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2026,38(3):875-884, DOI: 10.18307/2026.0300
Abstract:
Phytoplankton over-proliferation and the associated algal blooms in lakes is a worldwide ecological challenge. In China, bloom control has predominantly relied on the Environmental Quality Standards for Surface Water, which emphasize total nitrogen and total phosphorus concentration controls. However, this concentration-based approach may yield high costs and low effectiveness, failing to achieve cost-efficient control under constrained management resources. The limiting factor theory offers a scientific basis for resolving this dilemma by identifying the key influencing factors of phytoplankton, thereby enhancing the precision and efficacy of management interventions. Grounded in Liebig‘s law of the minimum (governing final yield) and Blackman‘s law of limiting factors (governing growth rate), this study systematically elucidates the multiple, interacting mechanisms that constrain phytoplankton, including nitrogen, phosphorus, light, temperature, hydrodynamics, and food-web regulation. We review three principal methodologies for identifying limiting factors—empirical threshold, empirical modeling, and experimental approaches—and discuss their respective applicability and limitations. Furthermore, the modulating roles of relatively uncontrollable environmental drivers, such as light and temperature, on the effectiveness of nutrient reduction on algal blooms are elaborated. From a precision lake management perspective, we propose three key prospects: i) clarifying external nutrient control strategies, ii) establishing a “climatic potential-realized performance” framework to evaluate phytoplankton nitrogen and phosphorus assimilation efficiency, and iii) elucidating nutrient redistribution among trophic levels under fishing-ban policies. These insights aim to address critical management questions—what to control, how much to control, where to control, and how to enhance the ecological capacity of lakes. This study focuses on constructing a selection framework to elucidate the integration of classical limiting factor theory with China‘s practical lake management needs, thereby identifying the most cost-effective technical measures from the existing technology pool to support precise algal bloom control.
Phytoplankton over-proliferation and the associated algal blooms in lakes is a worldwide ecological challenge. In China, bloom control has predominantly relied on the Environmental Quality Standards for Surface Water, which emphasize total nitrogen and total phosphorus concentration controls. However, this concentration-based approach may yield high costs and low effectiveness, failing to achieve cost-efficient control under constrained management resources. The limiting factor theory offers a scientific basis for resolving this dilemma by identifying the key influencing factors of phytoplankton, thereby enhancing the precision and efficacy of management interventions. Grounded in Liebig‘s law of the minimum (governing final yield) and Blackman‘s law of limiting factors (governing growth rate), this study systematically elucidates the multiple, interacting mechanisms that constrain phytoplankton, including nitrogen, phosphorus, light, temperature, hydrodynamics, and food-web regulation. We review three principal methodologies for identifying limiting factors—empirical threshold, empirical modeling, and experimental approaches—and discuss their respective applicability and limitations. Furthermore, the modulating roles of relatively uncontrollable environmental drivers, such as light and temperature, on the effectiveness of nutrient reduction on algal blooms are elaborated. From a precision lake management perspective, we propose three key prospects: i) clarifying external nutrient control strategies, ii) establishing a “climatic potential-realized performance” framework to evaluate phytoplankton nitrogen and phosphorus assimilation efficiency, and iii) elucidating nutrient redistribution among trophic levels under fishing-ban policies. These insights aim to address critical management questions—what to control, how much to control, where to control, and how to enhance the ecological capacity of lakes. This study focuses on constructing a selection framework to elucidate the integration of classical limiting factor theory with China‘s practical lake management needs, thereby identifying the most cost-effective technical measures from the existing technology pool to support precise algal bloom control.
Wang Cong, Wang Zhi, Li Enhua, Zhang Lu, Liu Xi, Li Shuyin, Li Ruiwen, Chen Shan, Xing Peng, Ao Sicheng, Lu Shaoyong, Tan Tiejun, Yang Jun
2026,38(3):885-902, DOI: 10.18307/2026.0301
Abstract:
The absence of a standardized damage assessment system for freshwater ecosystems significantly impedes the implementation of environmental justice and ecological compensation mechanisms in China. To address this gap, we developed a comprehensive assessment framework based on national technical guidelines for ecological and environmental damage assessment and the practical requirements of public interest litigation for environmental protection. This system integrates three dimensions—environmental quality, biological integrity, and ecological function—and is structured hierarchically into 1 overall objective, 2 sub-objectives, 8 criteria, and 27 indicators. Ecological baselines for each indicator were established using the trisection and quartile methods, with hierarchical formulas enabling stepwise aggregation from indicators to the overall objective. Ecosystem damage severity is quantified using an ecological damage index (EDI), with thresholds of 1.2, 1.5, and 2.0 corresponding to mild, moderate, and severe damage, respectively. The system was validated through case studies in Lake Honghu and a river in Xianning, Hubei Province. To enhance evaluation efficiency, sensitivity and accuracy analyses of the criteria were conducted, leading to the development of an optimized set of assessment criteria combinations with high accuracy (R2＞0.9, RMSE＜0.1). Non-core indicators within each criterion were subsequently eliminated through correlation analysis, resulting in a prioritized four-level combination scheme comprising 8, 7, 6, and 5 criteria, encompassing 13 to 21 indicators in total. The establishment and application of this assessment system not only advance the theoretical foundation for aquatic ecological damage assessment in China but also provide robust methodological support for ecological and environmental law enforcement and compensation practices.
The absence of a standardized damage assessment system for freshwater ecosystems significantly impedes the implementation of environmental justice and ecological compensation mechanisms in China. To address this gap, we developed a comprehensive assessment framework based on national technical guidelines for ecological and environmental damage assessment and the practical requirements of public interest litigation for environmental protection. This system integrates three dimensions—environmental quality, biological integrity, and ecological function—and is structured hierarchically into 1 overall objective, 2 sub-objectives, 8 criteria, and 27 indicators. Ecological baselines for each indicator were established using the trisection and quartile methods, with hierarchical formulas enabling stepwise aggregation from indicators to the overall objective. Ecosystem damage severity is quantified using an ecological damage index (EDI), with thresholds of 1.2, 1.5, and 2.0 corresponding to mild, moderate, and severe damage, respectively. The system was validated through case studies in Lake Honghu and a river in Xianning, Hubei Province. To enhance evaluation efficiency, sensitivity and accuracy analyses of the criteria were conducted, leading to the development of an optimized set of assessment criteria combinations with high accuracy (R2＞0.9, RMSE＜0.1). Non-core indicators within each criterion were subsequently eliminated through correlation analysis, resulting in a prioritized four-level combination scheme comprising 8, 7, 6, and 5 criteria, encompassing 13 to 21 indicators in total. The establishment and application of this assessment system not only advance the theoretical foundation for aquatic ecological damage assessment in China but also provide robust methodological support for ecological and environmental law enforcement and compensation practices.
2026,38(3):903-918, DOI: 10.18307/2026.0302
Abstract:
The construction of dams and reservoirs has profoundly altered the natural flow regimes of nearly two-thirds of the world‘s major rivers exceeding 1000 kilometers in length. With more than 90000 reservoirs, China ranks first in the world for the number of reservoirs. A series of complex factors, including the dam‘s trapping effect, hydraulic scheduling, local hydrometeorology, sediment inputs etc., not only shape reservoir sediments as a unique habitat, but also influence the diversity and functionality of microbial communities in the sediments. Microorganisms are the fundamental drivers of material cycling in the aquatic environment system and have important influences on the structure of watershed ecosystem, biogeochemical cycling of elements, global climate change, etc. Reservoirs alter sediment microbial communities not only via the changes of a variety of physical, chemical, and biological conditions, but also by dynamically influencing the spatiotemporal distribution of environmental-ecological conditions. In response, microbial communities in sediment also react by altering surrounding environmental conditions to some extent. Existing studies on individual factors, although relatively complete, lack systematicity, which hinders further in-depth understanding of the important interactions between microorganisms and hydraulic and ecological environment. Therefore, 189 related research articles have been collected and analyzed by 7th May, 2025, and this article reviews the physical, chemical, ecological impacts of reservoirs on sediment microbial communities, classifies and summarizes a series of responses of sediment microbial communities under hydrological regulation, and summarizes the environmental and ecological impacts brought by microbial communities. Results show that most of the existing studies consider reservoirs as lake-like habitats, and few studies consider changes in hydraulic conditions or special characteristics of the habitat; Although there are studies targeting microorganisms in sediments of water reservoirs, they are more focused on the biogeographical distribution patterns and less on the interactions between environment and microbial communities. Faced with the deficiencies in current research, it is recommended to strengthen the integration of interdisciplinary fields and to carry out in-depth related research in the fields of ecological and environmental effects of microbial communities, application of microbial ecology techniques and theories, development of big data and artificial intelligence models, global climate change and greenhouse gas emission reduction, etc.
The construction of dams and reservoirs has profoundly altered the natural flow regimes of nearly two-thirds of the world‘s major rivers exceeding 1000 kilometers in length. With more than 90000 reservoirs, China ranks first in the world for the number of reservoirs. A series of complex factors, including the dam‘s trapping effect, hydraulic scheduling, local hydrometeorology, sediment inputs etc., not only shape reservoir sediments as a unique habitat, but also influence the diversity and functionality of microbial communities in the sediments. Microorganisms are the fundamental drivers of material cycling in the aquatic environment system and have important influences on the structure of watershed ecosystem, biogeochemical cycling of elements, global climate change, etc. Reservoirs alter sediment microbial communities not only via the changes of a variety of physical, chemical, and biological conditions, but also by dynamically influencing the spatiotemporal distribution of environmental-ecological conditions. In response, microbial communities in sediment also react by altering surrounding environmental conditions to some extent. Existing studies on individual factors, although relatively complete, lack systematicity, which hinders further in-depth understanding of the important interactions between microorganisms and hydraulic and ecological environment. Therefore, 189 related research articles have been collected and analyzed by 7th May, 2025, and this article reviews the physical, chemical, ecological impacts of reservoirs on sediment microbial communities, classifies and summarizes a series of responses of sediment microbial communities under hydrological regulation, and summarizes the environmental and ecological impacts brought by microbial communities. Results show that most of the existing studies consider reservoirs as lake-like habitats, and few studies consider changes in hydraulic conditions or special characteristics of the habitat; Although there are studies targeting microorganisms in sediments of water reservoirs, they are more focused on the biogeographical distribution patterns and less on the interactions between environment and microbial communities. Faced with the deficiencies in current research, it is recommended to strengthen the integration of interdisciplinary fields and to carry out in-depth related research in the fields of ecological and environmental effects of microbial communities, application of microbial ecology techniques and theories, development of big data and artificial intelligence models, global climate change and greenhouse gas emission reduction, etc.
Li Xingyue, Liu Xiaomin, Liu Tingxi, Zhang Sheng, Wang Zihang, Lu Zongfu, Wang Wenjuan, Yang Yaotian
2026,38(3):919-930, DOI: 10.18307/2026.0311
Abstract:
In 2022, frequent cyanobacterial blooms occurred in Lake Hulun, covering nearly the entire lake surface, degrading aquatic landscapes, and posing serious threats to ecosystem health. To investigate the drivers of these large-scale blooms, water samples were collected from surface, middle, and bottom layers at 13 sampling sites during spring, summer, and autumn of 2022. Cyanobacterial species composition, abundance, biomass, and key water quality indicators were analyzed. A total of 22 cyanobacterial species were identified, with 10 dominant groups observed over the study period.Microcystis spp. remained the dominant genus across all seasons. The abundance and biomass of cyanobacteria varied significantly in different periods and depths. The abundance (2.58×109 cells/L) and biomass (3.30×102 mg/L) of cyanobacteria in summer were 1-2 orders of magnitude higher than those in spring and autumn. In spring, the abundance and biomass of cyanobacteria were the highest in the bottom layer of the lake, and the highest in the surface layer of the lake in summer and autumn. Correlation and redundancy analyses revealed seasonal differences in influencing factors, identifying water temperature, nitrogen and phosphorus concentrations, dissolved oxygen, and pH as key environmental drivers of bloom dynamics. For management, we recommend moderate nutrient control with a dual nitrogen-phosphorus reduction strategy, along with enhanced bloom prediction, early warning, and emergency response capabilities. These measures are essential for mitigating bloom risks in eutrophic lakes such as Lake Hulun and may inform future cyanobacterial bloom control strategies in similar ecosystems.
In 2022, frequent cyanobacterial blooms occurred in Lake Hulun, covering nearly the entire lake surface, degrading aquatic landscapes, and posing serious threats to ecosystem health. To investigate the drivers of these large-scale blooms, water samples were collected from surface, middle, and bottom layers at 13 sampling sites during spring, summer, and autumn of 2022. Cyanobacterial species composition, abundance, biomass, and key water quality indicators were analyzed. A total of 22 cyanobacterial species were identified, with 10 dominant groups observed over the study period.Microcystis spp. remained the dominant genus across all seasons. The abundance and biomass of cyanobacteria varied significantly in different periods and depths. The abundance (2.58×109 cells/L) and biomass (3.30×102 mg/L) of cyanobacteria in summer were 1-2 orders of magnitude higher than those in spring and autumn. In spring, the abundance and biomass of cyanobacteria were the highest in the bottom layer of the lake, and the highest in the surface layer of the lake in summer and autumn. Correlation and redundancy analyses revealed seasonal differences in influencing factors, identifying water temperature, nitrogen and phosphorus concentrations, dissolved oxygen, and pH as key environmental drivers of bloom dynamics. For management, we recommend moderate nutrient control with a dual nitrogen-phosphorus reduction strategy, along with enhanced bloom prediction, early warning, and emergency response capabilities. These measures are essential for mitigating bloom risks in eutrophic lakes such as Lake Hulun and may inform future cyanobacterial bloom control strategies in similar ecosystems.
2026,38(3):931-942, DOI: 10.18307/2026.0312
Abstract:
The Danjiangkou Reservoir serves as a critical water source for the middle route of the South-to-North Water Diversion Project and is designated as a national first-level drinking water protection zone. Since the project‘s impoundment in 2014, the overall water quality in the reservoir area has consistently met or exceeded Class II standards, underscoring its vital ecological and water resource functions. Water level fluctuation, as a key operational parameter, directly shapes the aquatic environment and indirectly influences the growth, distribution, and diversity of phytoplankton. To evaluate how water-level-induced habitat changes affect phytoplankton functional groups in the Danku District of Danjiangkou Reservoir, this study conducted sampling and analysis during high-water (October-December 2023) and low-water (April-June 2024) periods. We examined the structure and composition of phytoplankton functional groups and the environmental drivers affecting them. A total of 128 phytoplankton species from 75 genera and 7 phyla were identified across varying spatiotemporal conditions. Chlorophyta (37.33%), Bacillariophyta (36.00%), and Cyanophyta (14.67%) dominated the phytoplankton community. Significant differences in functional group composition were observed across time and space. In total, 26 functional groups were identified, including groups N and P (adapted to mixed water columns), Y and T (suited to stagnant waters), and generalist groups M and Lo. During the high-water period, functional group B dominated in the main reservoir, whereas groups MP, P, and Lo were dominant during the low-water period. In the tributaries, groups M, Lo, and S1 prevailed in the high-water period, while groups TC and B dominated in the low-water period. Redundancy analysis revealed that pH, turbidity, nitrate nitrogen, and phosphate were the primary environmental factors influencing dominant functional groups. Q-index-based water quality assessment indicated that the main reservoir water quality was generally “good”, while tributary water quality ranged from “poor” to “good”. These findings suggest that although water quality remains stable in the main reservoir, tributaries experience notable nutrient pollution impacts on phytoplankton communities during high-water periods, highlighting the need for management attention to external inputs under high-water conditions.
The Danjiangkou Reservoir serves as a critical water source for the middle route of the South-to-North Water Diversion Project and is designated as a national first-level drinking water protection zone. Since the project‘s impoundment in 2014, the overall water quality in the reservoir area has consistently met or exceeded Class II standards, underscoring its vital ecological and water resource functions. Water level fluctuation, as a key operational parameter, directly shapes the aquatic environment and indirectly influences the growth, distribution, and diversity of phytoplankton. To evaluate how water-level-induced habitat changes affect phytoplankton functional groups in the Danku District of Danjiangkou Reservoir, this study conducted sampling and analysis during high-water (October-December 2023) and low-water (April-June 2024) periods. We examined the structure and composition of phytoplankton functional groups and the environmental drivers affecting them. A total of 128 phytoplankton species from 75 genera and 7 phyla were identified across varying spatiotemporal conditions. Chlorophyta (37.33%), Bacillariophyta (36.00%), and Cyanophyta (14.67%) dominated the phytoplankton community. Significant differences in functional group composition were observed across time and space. In total, 26 functional groups were identified, including groups N and P (adapted to mixed water columns), Y and T (suited to stagnant waters), and generalist groups M and Lo. During the high-water period, functional group B dominated in the main reservoir, whereas groups MP, P, and Lo were dominant during the low-water period. In the tributaries, groups M, Lo, and S1 prevailed in the high-water period, while groups TC and B dominated in the low-water period. Redundancy analysis revealed that pH, turbidity, nitrate nitrogen, and phosphate were the primary environmental factors influencing dominant functional groups. Q-index-based water quality assessment indicated that the main reservoir water quality was generally “good”, while tributary water quality ranged from “poor” to “good”. These findings suggest that although water quality remains stable in the main reservoir, tributaries experience notable nutrient pollution impacts on phytoplankton communities during high-water periods, highlighting the need for management attention to external inputs under high-water conditions.
2026,38(3):943-954, DOI: 10.18307/2026.0313
Abstract:
Mesotrophic lakes and reservoirs, as critical sources of drinking water, exhibit unclear mechanisms governing the occurrence of occasional algal blooms and the dynamics of nutrient limitation. This study investigated Duihekou Reservoir in Zhejiang Province through four years ofin situmonitoring to elucidate fluctuations in algal growth rates and their dynamic coupling with intracellular nutrient quotas. Results indicated that during the diatom-dominated phase (December-April, DIA), thein situalgal growth rate varied markedly from -1.10 d-1 to 2.76 d-1, whereas during the cyanobacteria-dominated phase (July-August, CYA), it ranged from -0.43 d-1 to 0.81 d-1—higher than values typically observed in eutrophic systems—suggesting a high potential for rapid algal proliferation in mesotrophic waters. Growth rates in the DIA phase were primarily governed by nitrogen cell quotas, which may be attributed to the suppression of chlorophyll synthesis and nitrogen assimilation efficiency under light and temperature limitations. Therefore, a springtime rise in temperature and light intensity, coupled with elevated cellular nitrogen content, could trigger diatom blooms. In contrast, growth rates in the CYA phase were co-regulated by phosphorus cell quotas and environmental phosphorus quotas. Maintaining total phosphorus below 22 μg/L (95% CI: 15-32 μg/L) could effectively suppress cyanobacterial blooms (chlorophyll-a＞10 μg/L). This study innovatively incorporates dynamic intracellular nutrient quotas to analyze algal growth mechanisms, overcoming the traditional reliance on ambient nutrient concentrations, algal biomass, or N ∶P ratios to determine nutrient limitation. The approach offers a new theoretical basis for water quality management and bloom forecasting in mesotrophic lakes and reservoirs.
Mesotrophic lakes and reservoirs, as critical sources of drinking water, exhibit unclear mechanisms governing the occurrence of occasional algal blooms and the dynamics of nutrient limitation. This study investigated Duihekou Reservoir in Zhejiang Province through four years ofin situmonitoring to elucidate fluctuations in algal growth rates and their dynamic coupling with intracellular nutrient quotas. Results indicated that during the diatom-dominated phase (December-April, DIA), thein situalgal growth rate varied markedly from -1.10 d-1 to 2.76 d-1, whereas during the cyanobacteria-dominated phase (July-August, CYA), it ranged from -0.43 d-1 to 0.81 d-1—higher than values typically observed in eutrophic systems—suggesting a high potential for rapid algal proliferation in mesotrophic waters. Growth rates in the DIA phase were primarily governed by nitrogen cell quotas, which may be attributed to the suppression of chlorophyll synthesis and nitrogen assimilation efficiency under light and temperature limitations. Therefore, a springtime rise in temperature and light intensity, coupled with elevated cellular nitrogen content, could trigger diatom blooms. In contrast, growth rates in the CYA phase were co-regulated by phosphorus cell quotas and environmental phosphorus quotas. Maintaining total phosphorus below 22 μg/L (95% CI: 15-32 μg/L) could effectively suppress cyanobacterial blooms (chlorophyll-a＞10 μg/L). This study innovatively incorporates dynamic intracellular nutrient quotas to analyze algal growth mechanisms, overcoming the traditional reliance on ambient nutrient concentrations, algal biomass, or N ∶P ratios to determine nutrient limitation. The approach offers a new theoretical basis for water quality management and bloom forecasting in mesotrophic lakes and reservoirs.
2026,38(3):955-969, DOI: 10.18307/2026.0314
Abstract:
Phosphorus is a key nutrient in lake ecosystems and a primary limiting factor for primary productivity, with its speciation and concentration significantly influencing phytoplankton community structure. To investigate the characteristics of phosphorus fractions and their effects on phytoplankton assemblages in Lake Changhu, a typical shallow lake in the middle and lower reaches of the Yangtze River, and to provide a scientific basis for its ecological restoration and precision management, we conducted seasonal sampling in March, May, September, and December 2024 at 10 sites, analyzing phosphorus forms, environmental variables, and phytoplankton community composition. Results showed that the annual average total phosphorus (TP) concentration was 0.117 mg/L, with levels ordered as September ＞ March ＞ May ＞ December and a decreasing gradient from west to east. Dissolved total phosphorus (DTP; mean of 0.060 mg/L) contributed slightly more to TP than particulate phosphorus (PP; mean of 0.056 mg/L). Seasonal variation in phosphorus forms was observed: PP dominated in March; PP slightly exceeded DTP in May; DTP prevailed in September and December, with dissolved organic phosphorus (DOP) predominant in September and dissolved inorganic phosphorus (DIP) in December. DOP in September was significantly higher than in other months. Phytoplankton were dominated by Cyanophyta, Chlorophyta, Bacillariophyta, and Cryptophyta. Non-metric multidimensional scaling and permutational multivariate analysis of variance revealed significant temporal variation in community structure, showing a clear seasonal succession: from Bacillariophyta + Cryptophyta + Chlorophyta in March to Cyanophyta + Chlorophyta in May, then Cyanophyta in September, and finally Cryptophyta + Bacillariophyta + Cyanophyta + Chlorophyta in December. Dominant species included Cyclotella sp. (Bacillariophyta) in March,Merismopedia minima(Cyanophyta) in May,Komma caudata(Cryptophyta) in December, and Microcystis spp. (Cyanophyta)—a bloom-forming genus—in September, which was also dominant in May. Redundancy analysis and partial least squares path modeling identified DOP, water temperature, DTP, and suspended solids as the most influential factors on phytoplankton community structure, with phosphorus fractions exerting significant direct effects. DOP showed the strongest effect, particularly promotingMicrocystis spp. abundance. These results demonstrate that phosphorus speciation significantly shapes phytoplankton community structure in Lake Changhu and highlight the importance of quantitative assessment of different phosphorus forms—especially DOP—for evaluating ecological risks in eutrophic shallow lakes.
Phosphorus is a key nutrient in lake ecosystems and a primary limiting factor for primary productivity, with its speciation and concentration significantly influencing phytoplankton community structure. To investigate the characteristics of phosphorus fractions and their effects on phytoplankton assemblages in Lake Changhu, a typical shallow lake in the middle and lower reaches of the Yangtze River, and to provide a scientific basis for its ecological restoration and precision management, we conducted seasonal sampling in March, May, September, and December 2024 at 10 sites, analyzing phosphorus forms, environmental variables, and phytoplankton community composition. Results showed that the annual average total phosphorus (TP) concentration was 0.117 mg/L, with levels ordered as September ＞ March ＞ May ＞ December and a decreasing gradient from west to east. Dissolved total phosphorus (DTP; mean of 0.060 mg/L) contributed slightly more to TP than particulate phosphorus (PP; mean of 0.056 mg/L). Seasonal variation in phosphorus forms was observed: PP dominated in March; PP slightly exceeded DTP in May; DTP prevailed in September and December, with dissolved organic phosphorus (DOP) predominant in September and dissolved inorganic phosphorus (DIP) in December. DOP in September was significantly higher than in other months. Phytoplankton were dominated by Cyanophyta, Chlorophyta, Bacillariophyta, and Cryptophyta. Non-metric multidimensional scaling and permutational multivariate analysis of variance revealed significant temporal variation in community structure, showing a clear seasonal succession: from Bacillariophyta + Cryptophyta + Chlorophyta in March to Cyanophyta + Chlorophyta in May, then Cyanophyta in September, and finally Cryptophyta + Bacillariophyta + Cyanophyta + Chlorophyta in December. Dominant species included Cyclotella sp. (Bacillariophyta) in March,Merismopedia minima(Cyanophyta) in May,Komma caudata(Cryptophyta) in December, and Microcystis spp. (Cyanophyta)—a bloom-forming genus—in September, which was also dominant in May. Redundancy analysis and partial least squares path modeling identified DOP, water temperature, DTP, and suspended solids as the most influential factors on phytoplankton community structure, with phosphorus fractions exerting significant direct effects. DOP showed the strongest effect, particularly promotingMicrocystis spp. abundance. These results demonstrate that phosphorus speciation significantly shapes phytoplankton community structure in Lake Changhu and highlight the importance of quantitative assessment of different phosphorus forms—especially DOP—for evaluating ecological risks in eutrophic shallow lakes.
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Available online: June 15, 2026
Abstract:
To elucidate the spatiotemporal succession patterns and environmental driving mechanisms of bacterial communities across different habitats in reservoirs within the semi-arid region of southern Ningxia, water and sediment samples were collected from eight typical reservoirs in Guyuan City during April, July, and October 2025. By integrating 16S rRNA gene high-throughput sequencing with the Trophic Level Index (TLI), Mantel tests, and Redundancy Analysis (RDA), this study investigated community structure, seasonal dynamics, and their relationships with environmental factors.The results indicated that the eight reservoirs exhibited a complete environmental gradient ranging from mesotrophic (Site S6) to hyper-eutrophic (Site S1) status based on TLI evaluation. Proteobacteria was the predominant phylum in both water (31.68%–36.49%) and sediment (38.16%–43.48%) habitats. In July, high temperatures and strong irradiance drove an explosive enrichment of Cyanobacteriota and its constituent order Synechococcales in the water column, resulting in a simplified community structure and a decline in α-diversity. In contrast, the sediment habitat remained relatively stable, enriching benthic-specific taxa such as Acidobacteriota and Chloroflexi, with α-diversity exhibiting a trend of seasonal accumulation.The environmental driving mechanisms demonstrated distinct habitat specificity. Water bacterial communities were significantly influenced by Total Nitrogen (TN), Total Phosphorus (TP), Permanganate Index (CODMn), and Nitrate Nitrogen (NO3-N) (P<0.01), while high summer temperatures and pH were identified as key physical factors reshaping community structure. Conversely, the succession of sediment communities was primarily regulated by Ammonium Nitrogen (NH4+-N), TP, and Salinity (SAL). This study systematically elucidates the seasonal variations in microbial community structures across different habitats in arid-region reservoirs, providing a scientific basis for regional water environment management.
To elucidate the spatiotemporal succession patterns and environmental driving mechanisms of bacterial communities across different habitats in reservoirs within the semi-arid region of southern Ningxia, water and sediment samples were collected from eight typical reservoirs in Guyuan City during April, July, and October 2025. By integrating 16S rRNA gene high-throughput sequencing with the Trophic Level Index (TLI), Mantel tests, and Redundancy Analysis (RDA), this study investigated community structure, seasonal dynamics, and their relationships with environmental factors.The results indicated that the eight reservoirs exhibited a complete environmental gradient ranging from mesotrophic (Site S6) to hyper-eutrophic (Site S1) status based on TLI evaluation. Proteobacteria was the predominant phylum in both water (31.68%–36.49%) and sediment (38.16%–43.48%) habitats. In July, high temperatures and strong irradiance drove an explosive enrichment of Cyanobacteriota and its constituent order Synechococcales in the water column, resulting in a simplified community structure and a decline in α-diversity. In contrast, the sediment habitat remained relatively stable, enriching benthic-specific taxa such as Acidobacteriota and Chloroflexi, with α-diversity exhibiting a trend of seasonal accumulation.The environmental driving mechanisms demonstrated distinct habitat specificity. Water bacterial communities were significantly influenced by Total Nitrogen (TN), Total Phosphorus (TP), Permanganate Index (CODMn), and Nitrate Nitrogen (NO3-N) (P<0.01), while high summer temperatures and pH were identified as key physical factors reshaping community structure. Conversely, the succession of sediment communities was primarily regulated by Ammonium Nitrogen (NH4+-N), TP, and Salinity (SAL). This study systematically elucidates the seasonal variations in microbial community structures across different habitats in arid-region reservoirs, providing a scientific basis for regional water environment management.
Available online: June 12, 2026
Abstract:
The dynamics of total phosphorus (TP) concentrations in shallow lakes are collectively driven by multiple environmental factors. The complexity of these underlying mechanisms is closely related to the lake"s physicochemical properties. Based on high-frequency data from national water quality, hydrological, and meteorological monitoring stations in the Lake Chaohu basin from 2021 to 2024, this study employed principal component analysis (PCA) and time-lag correlation analysis to elucidate the variation patterns of TP concentrations, identify the primary driving factors, and determine the risk threshold grades of environmental factors associated with TP exceedance or abrupt changes. The results indicated that water temperature (WT), dissolved oxygen (DO), and algal density (AD) were the dominant environmental drivers governing TP fluctuations in Lake Chaohu, with a cumulative contribution rate exceeding 50%. Wind speed (WD) was identified as a key meteorological factor. Furthermore, this study identified a cascading driving process of TP dynamics with distinct time-lag effects in Lake Chaohu. Specifically, a rise in WT during summer was followed by an increase in algal biomass after 4 days, accompanied by a significant decline in DO. The decrease in DO rapidly induced an elevation in water TP concentration within 24 hours, indicating a rapid response of phosphorus release at the sediment-water microinterface. The peak impact of AD on TP concentration occurred with a 3-day lag, attributable to both direct phosphorus release during algal growth and senescence, and indirect effects via DO consumption. Based on these findings, risk threshold grades for DO (7.69, 7.08, 6.72 mg/L) and AD (9.80, 15.64, 21.14 × 10? cells/L) were established for different TP concentration intervals in Lake Chaohu: (0.05, 0.075], (0.075, 0.1], and >0.1 mg/L. These results provide a crucial temporal decision-making basis for TP risk early warning and precision management in Lake Chaohu.
The dynamics of total phosphorus (TP) concentrations in shallow lakes are collectively driven by multiple environmental factors. The complexity of these underlying mechanisms is closely related to the lake"s physicochemical properties. Based on high-frequency data from national water quality, hydrological, and meteorological monitoring stations in the Lake Chaohu basin from 2021 to 2024, this study employed principal component analysis (PCA) and time-lag correlation analysis to elucidate the variation patterns of TP concentrations, identify the primary driving factors, and determine the risk threshold grades of environmental factors associated with TP exceedance or abrupt changes. The results indicated that water temperature (WT), dissolved oxygen (DO), and algal density (AD) were the dominant environmental drivers governing TP fluctuations in Lake Chaohu, with a cumulative contribution rate exceeding 50%. Wind speed (WD) was identified as a key meteorological factor. Furthermore, this study identified a cascading driving process of TP dynamics with distinct time-lag effects in Lake Chaohu. Specifically, a rise in WT during summer was followed by an increase in algal biomass after 4 days, accompanied by a significant decline in DO. The decrease in DO rapidly induced an elevation in water TP concentration within 24 hours, indicating a rapid response of phosphorus release at the sediment-water microinterface. The peak impact of AD on TP concentration occurred with a 3-day lag, attributable to both direct phosphorus release during algal growth and senescence, and indirect effects via DO consumption. Based on these findings, risk threshold grades for DO (7.69, 7.08, 6.72 mg/L) and AD (9.80, 15.64, 21.14 × 10? cells/L) were established for different TP concentration intervals in Lake Chaohu: (0.05, 0.075], (0.075, 0.1], and >0.1 mg/L. These results provide a crucial temporal decision-making basis for TP risk early warning and precision management in Lake Chaohu.
Available online: June 12, 2026
Abstract:
The operation of the Three Gorges Reservoir (TGR) has altered water and sediment processes in the middle and lower reaches of the Yangtze River, affecting the adjustment characteristics of scouring and sedimentation in the branch channels as well as the flow distribution relationships among relatively balanced channels. Thereby exerting a cascading impact on flood control, navigation, and river management. Given the current limitations in understanding the adjustment patterns of branch channels under the influence of water and sediment conditions altered by the operation of cascade reservoi, this study utilizes measured hydrological and topographic data from 2003 to 2023. Taking eleven typical distributary channels in the Chenglingji to Jiujiang section as examples, it employs a distributary channel classification method based on dynamic diversion ratios to investigate channel type conversion phenomena and analyze their driving mechanisms. The study reveals：（1）The method for classifying branch channels based on dynamic diversion ratios demonstrates good adaptability in classifying branch channels in the middle and lower reaches of the Yangtze River and identifying their typological transitions under different operating modes of the TGR（2）Following the TGR impoundment, the branch channels exhibited different adjustment patterns during various periods. Since 2013, the section from Chenglingji to Jiujiang has been dominated by Type I branch channels (where the main channel corresponds to a low-flow-dominant branch channel), while in Type II branch channels (where the main channel corresponds to a low-flow-prone branch), the Jiepaoxin Sandbar branch section, Luxi Kou, Jiayu, and Yanzowo channels have transitioned to Type I branch channels, shifting from a “main channel shortening, branch channel lengthening” pattern to a “main channel lengthening, branch channel shortening” pattern;（3）For the transformation of Type II distributary channels into Type I channels, altered hydrological and sediment conditions were the primary driver. Navigation improvement projects demonstrated a promoting effect on this transformation in most distributary channels. After 2013, the frequency and duration of flow levels between 20,000 and 30,000 m3/s increased, leading to intensified scouring in the main channel branch at these flow levels. with some branches evolving into Class I distributary channels. It is foreseeable that branched river systems in the middle and lower reaches of the Yangtze River will predominantly shift toward Class I, characterized by an adjustment pattern where the main channel grows while tributaries diminish.
The operation of the Three Gorges Reservoir (TGR) has altered water and sediment processes in the middle and lower reaches of the Yangtze River, affecting the adjustment characteristics of scouring and sedimentation in the branch channels as well as the flow distribution relationships among relatively balanced channels. Thereby exerting a cascading impact on flood control, navigation, and river management. Given the current limitations in understanding the adjustment patterns of branch channels under the influence of water and sediment conditions altered by the operation of cascade reservoi, this study utilizes measured hydrological and topographic data from 2003 to 2023. Taking eleven typical distributary channels in the Chenglingji to Jiujiang section as examples, it employs a distributary channel classification method based on dynamic diversion ratios to investigate channel type conversion phenomena and analyze their driving mechanisms. The study reveals：（1）The method for classifying branch channels based on dynamic diversion ratios demonstrates good adaptability in classifying branch channels in the middle and lower reaches of the Yangtze River and identifying their typological transitions under different operating modes of the TGR（2）Following the TGR impoundment, the branch channels exhibited different adjustment patterns during various periods. Since 2013, the section from Chenglingji to Jiujiang has been dominated by Type I branch channels (where the main channel corresponds to a low-flow-dominant branch channel), while in Type II branch channels (where the main channel corresponds to a low-flow-prone branch), the Jiepaoxin Sandbar branch section, Luxi Kou, Jiayu, and Yanzowo channels have transitioned to Type I branch channels, shifting from a “main channel shortening, branch channel lengthening” pattern to a “main channel lengthening, branch channel shortening” pattern;（3）For the transformation of Type II distributary channels into Type I channels, altered hydrological and sediment conditions were the primary driver. Navigation improvement projects demonstrated a promoting effect on this transformation in most distributary channels. After 2013, the frequency and duration of flow levels between 20,000 and 30,000 m3/s increased, leading to intensified scouring in the main channel branch at these flow levels. with some branches evolving into Class I distributary channels. It is foreseeable that branched river systems in the middle and lower reaches of the Yangtze River will predominantly shift toward Class I, characterized by an adjustment pattern where the main channel grows while tributaries diminish.
Available online: June 12, 2026
Abstract:
In river ecosystems, environmental filtering selects for aquatic biological functional traits that exhibit specific responses to catchment-scale land use patterns. To elucidate the mechanisms by which spatial land use configurations influence the distribution of aquatic biological functional traits, this study conducted systematic surveys at 30 sampling sites in the Chishui River Basin from 2022 to 2024. Four macroinvertebrate functional groups were identified through functional trait matrix analysis and cluster analysis. Significant traits for each functional group were screened using Gini coefficients derived from random forest models. Multiple linear regression analysis was employed to examine the variation in explanatory power (R2) of habitat factors within buffer zones of 50, 100, 250, 500, 1000, and 2000 m. Based on the principle of R2 maximization, a 500-m circular buffer zone was determined as the optimal spatial scale for each sampling site. Generalized additive models were subsequently applied to identify the response intervals of buffer zone land use structure that maintain stability of each functional assemblage: forest land 15.21%–44.89%, cropland <5.29%, built-up land 1.21%–9.00%, bare land >32.49%, and water body 0.64%–10.89%, along with critical habitat parameter ranges (water temperature 15–24℃, pH 5.02–8.81, NH?-N 0.31–0.45 mg/L, substrate particle size 36–188 mm). This study further quantified the effects of natural land proportion on the suitability of each functional group: a 10% increase in natural land corresponded to suitability increases of 0.33 and 0.34 units for scrapers and predators, respectively; filters and collectors also exhibited significant suitability improvements with elevated natural land proportion. These findings reveal the response relationships and underlying mechanisms among land use, habitat factors, and macroinvertebrate functional groups, providing quantitative foundations for catchment ecological conservation and land management.
In river ecosystems, environmental filtering selects for aquatic biological functional traits that exhibit specific responses to catchment-scale land use patterns. To elucidate the mechanisms by which spatial land use configurations influence the distribution of aquatic biological functional traits, this study conducted systematic surveys at 30 sampling sites in the Chishui River Basin from 2022 to 2024. Four macroinvertebrate functional groups were identified through functional trait matrix analysis and cluster analysis. Significant traits for each functional group were screened using Gini coefficients derived from random forest models. Multiple linear regression analysis was employed to examine the variation in explanatory power (R2) of habitat factors within buffer zones of 50, 100, 250, 500, 1000, and 2000 m. Based on the principle of R2 maximization, a 500-m circular buffer zone was determined as the optimal spatial scale for each sampling site. Generalized additive models were subsequently applied to identify the response intervals of buffer zone land use structure that maintain stability of each functional assemblage: forest land 15.21%–44.89%, cropland <5.29%, built-up land 1.21%–9.00%, bare land >32.49%, and water body 0.64%–10.89%, along with critical habitat parameter ranges (water temperature 15–24℃, pH 5.02–8.81, NH?-N 0.31–0.45 mg/L, substrate particle size 36–188 mm). This study further quantified the effects of natural land proportion on the suitability of each functional group: a 10% increase in natural land corresponded to suitability increases of 0.33 and 0.34 units for scrapers and predators, respectively; filters and collectors also exhibited significant suitability improvements with elevated natural land proportion. These findings reveal the response relationships and underlying mechanisms among land use, habitat factors, and macroinvertebrate functional groups, providing quantitative foundations for catchment ecological conservation and land management.
Available online: June 11, 2026
Abstract:
Lakes are vital ecosystems providing essential functions such as water conservation, climate regulation, and biodiversity maintenance. Jiangsu Province, located in the lower reaches of the Yangtze and Huaihe rivers, is a typical region of shallow lakes in China where eutrophication remains a prominent issue. Due to the distinct natural geographical backgrounds and socio-economic development levels between Northern and Southern Jiangsu, the trophic states and driving mechanisms of these lakes exhibit significant regional heterogeneity. Based on long-term monthly monitoring data from 2011 to 2023, this study systematically analyzed the spatiotemporal evolution of water quality indicators and the comprehensive Trophic Level Index (TLI) in seven typical lakes: Lake Luoma, Lake Hongze, Lake Baima, and Lake Gaoyou in Northern Jiangsu, and Lake Ge, Lake Changdang, and Lake Gucheng in Southern Jiangsu. The driving mechanisms were further quantified using Random Forest (RF) models and Pearson correlation analysis. The results showed that over the past decade, the water quality of typical lakes in Jiangsu exhibited a distinct regional divergence. In terms of trophic status, Lake Ge and Lake Changdang exhibited the highest degree of eutrophication, ranging from light to moderate eutrophic states. Lake Baima, Lake Hongze, and Lake Gaoyou were categorized as lightly eutrophic, while Lake Luoma and Lake Gucheng were positioned within the critical transition range from mesotrophic to lightly eutrophic states. Trend analysis revealed that lakes in Southern Jiangsu exhibited significant water quality improvements, particularly Lake Ge and Lake Changdang, which were historically moderately eutrophic. Specifically, TN and TP concentrations in Lake Ge decreased by 1.96 mg/L and 0.087 mg/L (a 48.3% reduction), respectively, with its TLI dropping by 9.4. Conversely, lakes in Northern Jiangsu experienced a deteriorating trend. Lake Luoma transitioned from mesotrophic to lightly eutrophic as its TLI rose by 7.4, while Lake Hongze and Lake Gaoyou TLI increased 6.6 and 5.4, respectively. TLI values ranged across the study area from 47.36 to 61.01, with Southern lakes generally maintaining higher absolute trophic levels but showing better remediation progress. In terms of seasonal variation, Northern lakes exhibited significant differences between flood and non-flood seasons, with TLI values significantly higher during the flood season, whereas Southern lakes remained relatively stable throughout the year. Driver analysis revealed that water quality in Northern lakes was highly sensitive to hydrometeorological fluctuations. Increased precipitation and the resulting surge in inflow volume acted as the primary drivers of exogenous nutrient loading, further exacerbated by internal release under high temperatures and wind disturbances. In contrast, the improvement in Southern lakes was mainly attributed to landuse optimization and strict pollution control. The reduction in farmland (acting as a "source") and the restoration of forests and wetlands (acting as "sinks") effectively intercepted runoff pollution. These findings highlight the complexity of lake management under climate change and non-point source pressures, providing a scientific basis for differentiated eutrophication control and regional water security strategies in Jiangsu Province.
Lakes are vital ecosystems providing essential functions such as water conservation, climate regulation, and biodiversity maintenance. Jiangsu Province, located in the lower reaches of the Yangtze and Huaihe rivers, is a typical region of shallow lakes in China where eutrophication remains a prominent issue. Due to the distinct natural geographical backgrounds and socio-economic development levels between Northern and Southern Jiangsu, the trophic states and driving mechanisms of these lakes exhibit significant regional heterogeneity. Based on long-term monthly monitoring data from 2011 to 2023, this study systematically analyzed the spatiotemporal evolution of water quality indicators and the comprehensive Trophic Level Index (TLI) in seven typical lakes: Lake Luoma, Lake Hongze, Lake Baima, and Lake Gaoyou in Northern Jiangsu, and Lake Ge, Lake Changdang, and Lake Gucheng in Southern Jiangsu. The driving mechanisms were further quantified using Random Forest (RF) models and Pearson correlation analysis. The results showed that over the past decade, the water quality of typical lakes in Jiangsu exhibited a distinct regional divergence. In terms of trophic status, Lake Ge and Lake Changdang exhibited the highest degree of eutrophication, ranging from light to moderate eutrophic states. Lake Baima, Lake Hongze, and Lake Gaoyou were categorized as lightly eutrophic, while Lake Luoma and Lake Gucheng were positioned within the critical transition range from mesotrophic to lightly eutrophic states. Trend analysis revealed that lakes in Southern Jiangsu exhibited significant water quality improvements, particularly Lake Ge and Lake Changdang, which were historically moderately eutrophic. Specifically, TN and TP concentrations in Lake Ge decreased by 1.96 mg/L and 0.087 mg/L (a 48.3% reduction), respectively, with its TLI dropping by 9.4. Conversely, lakes in Northern Jiangsu experienced a deteriorating trend. Lake Luoma transitioned from mesotrophic to lightly eutrophic as its TLI rose by 7.4, while Lake Hongze and Lake Gaoyou TLI increased 6.6 and 5.4, respectively. TLI values ranged across the study area from 47.36 to 61.01, with Southern lakes generally maintaining higher absolute trophic levels but showing better remediation progress. In terms of seasonal variation, Northern lakes exhibited significant differences between flood and non-flood seasons, with TLI values significantly higher during the flood season, whereas Southern lakes remained relatively stable throughout the year. Driver analysis revealed that water quality in Northern lakes was highly sensitive to hydrometeorological fluctuations. Increased precipitation and the resulting surge in inflow volume acted as the primary drivers of exogenous nutrient loading, further exacerbated by internal release under high temperatures and wind disturbances. In contrast, the improvement in Southern lakes was mainly attributed to landuse optimization and strict pollution control. The reduction in farmland (acting as a "source") and the restoration of forests and wetlands (acting as "sinks") effectively intercepted runoff pollution. These findings highlight the complexity of lake management under climate change and non-point source pressures, providing a scientific basis for differentiated eutrophication control and regional water security strategies in Jiangsu Province.
Available online: June 11, 2026
Abstract:
Sediment nitrogen and phosphorus pollution has become a critical factor limiting the sustained improvement of lake water quality in China. To address this issue, this study reviewed domestic and international literature and monitoring data from 2000 to 2022, obtaining surface sediment data from 131 lakes within China"s five major lake zones—Eastern Plain Lakes (EPL), Northeast Plain & Mountain Lakes (NPML), Inner Mongolia-Xinjiang Plateau Lakes (IXML), Yunnan-Guizhou Plateau Lakes (YGPL), and Tibetan Plateau Lakes (TPL). The Single Pollution Index (Pi) method was employed to evaluate the pollution status and spatial differentiation characteristics of Total Nitrogen (TN) and Total Phosphorus (TP). Furthermore, by incorporating case studies, this research systematically reviews the nearly 70-year evolution of management paradigms for lake sediments in China. The key findings are as follows: (1) TN pollution in lake sediments is relatively severe overall (Average Pi = 4.54), reaching a heavy pollution level, with a spatial pattern showing higher levels in the northeast and southwest and lower levels in central and western regions. The pollution degree across lake zones, in descending order, is: NPML Pi = 6.90 > YGPL (5.89) > IXML (5.08) > EPL (4.09) > TPL (4.08). In contrast, TP pollution is relatively lighter overall (Average Pi = 1.41), with the order YGPL Pi = 2.26 > NPML (1.96) > IXML (1.32) > EPL (1.27) > TPL (0.94), at a light pollution level. This indicates that the relatively severe TN pollution and the TP pollution in Chinese lakes are primarily influenced by localized anthropogenic inputs and regional natural backgrounds. (2) The management of sediment pollution in China has undergone a clear three-stage developmental progression: from engineering dredging (1950–1998) to environmental dredging (1998–2015), and then to the current stage of systematic governance (2015–present). (3) For future management, a systematic approach guided by the principle of "zoning, classification, and gradation" must be implemented. Efforts should focus on strengthening foundational surveys and database construction, promoting the classified recycling and utilization of sediments based on pollution characteristics, and establishing long-term guarantee mechanisms, to achieve effective internal pollution control and the long-term restoration of lake ecosystems in China.
Sediment nitrogen and phosphorus pollution has become a critical factor limiting the sustained improvement of lake water quality in China. To address this issue, this study reviewed domestic and international literature and monitoring data from 2000 to 2022, obtaining surface sediment data from 131 lakes within China"s five major lake zones—Eastern Plain Lakes (EPL), Northeast Plain & Mountain Lakes (NPML), Inner Mongolia-Xinjiang Plateau Lakes (IXML), Yunnan-Guizhou Plateau Lakes (YGPL), and Tibetan Plateau Lakes (TPL). The Single Pollution Index (Pi) method was employed to evaluate the pollution status and spatial differentiation characteristics of Total Nitrogen (TN) and Total Phosphorus (TP). Furthermore, by incorporating case studies, this research systematically reviews the nearly 70-year evolution of management paradigms for lake sediments in China. The key findings are as follows: (1) TN pollution in lake sediments is relatively severe overall (Average Pi = 4.54), reaching a heavy pollution level, with a spatial pattern showing higher levels in the northeast and southwest and lower levels in central and western regions. The pollution degree across lake zones, in descending order, is: NPML Pi = 6.90 > YGPL (5.89) > IXML (5.08) > EPL (4.09) > TPL (4.08). In contrast, TP pollution is relatively lighter overall (Average Pi = 1.41), with the order YGPL Pi = 2.26 > NPML (1.96) > IXML (1.32) > EPL (1.27) > TPL (0.94), at a light pollution level. This indicates that the relatively severe TN pollution and the TP pollution in Chinese lakes are primarily influenced by localized anthropogenic inputs and regional natural backgrounds. (2) The management of sediment pollution in China has undergone a clear three-stage developmental progression: from engineering dredging (1950–1998) to environmental dredging (1998–2015), and then to the current stage of systematic governance (2015–present). (3) For future management, a systematic approach guided by the principle of "zoning, classification, and gradation" must be implemented. Efforts should focus on strengthening foundational surveys and database construction, promoting the classified recycling and utilization of sediments based on pollution characteristics, and establishing long-term guarantee mechanisms, to achieve effective internal pollution control and the long-term restoration of lake ecosystems in China.
Available online: June 10, 2026
Abstract:
The global attention to the pollution of nutrients and per-and polyfluoroalkyl substances (PFAS) is increasing, which requires the development of more efficient and low-cost remediation strategies. This study focuses on the remediation of nitrogen, phosphorus, and various PFAS components by aquatic plants, representing a sustainable alternative to traditional physical and chemical methods. In order to overcome the limitations of traditional experimental methods, we constructed a comprehensive dataset by systematically searching for literature in databases such as CNKI, Science Direct, and Web of Science from 2015 to 2025. The final database contains 128 independent experimental records, covering pollutant remediation data under different experimental conditions, ensuring the universality of research conclusions. The input features cover 14 dimensions, including aquatic plant types (submerged, emergent, and floating), planting density, environmental temperature, and initial concentrations of nitrogen, phosphorus, and eight specific PFAS components (such as PFOS, PFOA, PFBA). In order to mitigate inherent systematic biases in multi-source literature data, this study implemented strict quality control protocols. For missing values of secondary environmental parameters, RF-based imputation is used for processing, which can better preserve the nonlinear structure of the data than simple mean replacement. All numerical features are standardized using StandardScaler to eliminate dimensional deviations. In addition, data heterogeneity was quantitatively evaluated using one-way analysis of variance (ANOVA) and effect measures (η2). The results indicate that planting density and temperature are the main sources of statistical heterogeneity, explaining 41.67% and 41.47% of the total variation, respectively (P<0.001). We comprehensively evaluated the impact of various factors on the removal rate of PFAS using Multi-objective Random Forest (MTRF), Multilayer Perceptron (MLP), Random Forest (RF), and Extreme Gradient Boosting (XGBoost) algorithms.?Use R2 and Root Mean Square Err (RMSE) as evaluation metrics for different models.The MTRF model achieved average R2 values of 0.68 and 0.72 in nitrogen removal and PFNA prediction, respectively, demonstrating substantial predictive ability significantly better than the MLP model with negative R2 values and inability to capture complex patterns. The in-depth mechanism explanation using the SHAP framework reveals that initial phosphorus concentration has a positive effect on nitrogen absorption, and phosphorus can promote nitrogen absorption by improving plant metabolic capacity. For PFAS, a threshold suppression effect was observed; Due to oxidative stress and enzyme activity inhibition caused by reactive oxygen species (ROS), high initial concentrations and extreme temperatures are negatively correlated with removal efficiency. Through virtual screening, Vallisneria natans was identified as the dominant species, possibly due to its strong root to stem transport ability and high bioaccumulation factor for PFAS. By optimizing the operating conditions, the optimal planting density for removing nutrients from Vallisneria natans is 19 plants/m2, and the optimal restoration time is 69 days; The optimal planting density for removing PFAS is 59 plants/m2, and the optimal restoration time is 34 days. The machine learning model established in this study not only provides accurate predictions for plant remediation efficiency under complex water quality conditions, but also provides theoretical basis and engineering decision support for low-cost and systematic treatment of water composite pollution.
The global attention to the pollution of nutrients and per-and polyfluoroalkyl substances (PFAS) is increasing, which requires the development of more efficient and low-cost remediation strategies. This study focuses on the remediation of nitrogen, phosphorus, and various PFAS components by aquatic plants, representing a sustainable alternative to traditional physical and chemical methods. In order to overcome the limitations of traditional experimental methods, we constructed a comprehensive dataset by systematically searching for literature in databases such as CNKI, Science Direct, and Web of Science from 2015 to 2025. The final database contains 128 independent experimental records, covering pollutant remediation data under different experimental conditions, ensuring the universality of research conclusions. The input features cover 14 dimensions, including aquatic plant types (submerged, emergent, and floating), planting density, environmental temperature, and initial concentrations of nitrogen, phosphorus, and eight specific PFAS components (such as PFOS, PFOA, PFBA). In order to mitigate inherent systematic biases in multi-source literature data, this study implemented strict quality control protocols. For missing values of secondary environmental parameters, RF-based imputation is used for processing, which can better preserve the nonlinear structure of the data than simple mean replacement. All numerical features are standardized using StandardScaler to eliminate dimensional deviations. In addition, data heterogeneity was quantitatively evaluated using one-way analysis of variance (ANOVA) and effect measures (η2). The results indicate that planting density and temperature are the main sources of statistical heterogeneity, explaining 41.67% and 41.47% of the total variation, respectively (P<0.001). We comprehensively evaluated the impact of various factors on the removal rate of PFAS using Multi-objective Random Forest (MTRF), Multilayer Perceptron (MLP), Random Forest (RF), and Extreme Gradient Boosting (XGBoost) algorithms.?Use R2 and Root Mean Square Err (RMSE) as evaluation metrics for different models.The MTRF model achieved average R2 values of 0.68 and 0.72 in nitrogen removal and PFNA prediction, respectively, demonstrating substantial predictive ability significantly better than the MLP model with negative R2 values and inability to capture complex patterns. The in-depth mechanism explanation using the SHAP framework reveals that initial phosphorus concentration has a positive effect on nitrogen absorption, and phosphorus can promote nitrogen absorption by improving plant metabolic capacity. For PFAS, a threshold suppression effect was observed; Due to oxidative stress and enzyme activity inhibition caused by reactive oxygen species (ROS), high initial concentrations and extreme temperatures are negatively correlated with removal efficiency. Through virtual screening, Vallisneria natans was identified as the dominant species, possibly due to its strong root to stem transport ability and high bioaccumulation factor for PFAS. By optimizing the operating conditions, the optimal planting density for removing nutrients from Vallisneria natans is 19 plants/m2, and the optimal restoration time is 69 days; The optimal planting density for removing PFAS is 59 plants/m2, and the optimal restoration time is 34 days. The machine learning model established in this study not only provides accurate predictions for plant remediation efficiency under complex water quality conditions, but also provides theoretical basis and engineering decision support for low-cost and systematic treatment of water composite pollution.
Available online: June 10, 2026
Abstract:
As global climate change intensifies, hydrological cycles are exhibiting increasingly pronounced non-stationary, multi-scale, and highly nonlinear behaviors. Traditional mechanistic models face significant challenges in fully capturing the meteorological–runoff response mechanisms, while deep learning approaches still struggle with long-term dependency modeling, spatial correlations, and sequence decoupling. To address these issues, we propose a hybrid forecasting model, JMD-Gformer, which combines Jump plus AM-FM Mode Decomposition (JMD), sparse directed graph networks, and Transformer-based architectures. In this framework, JMD decomposes the non-stationary runoff time series into jump components (representing abrupt runoff events) and periodic components (capturing seasonal and inter-annual fluctuations), effectively mitigating noise and mode aliasing. Additionally, we construct a sparse directed graph based on meteorology-hydrology nodes to represent the upstream-downstream interactions. The model further incorporates a multi-head self-attention mechanism for long-range temporal dependencies. Experiments conducted on multi-time-scale runoff predictions in the Daliao River Basin demonstrate that, compared to the second-best benchmark model, JMD-Gformer reduces MAPE and RMSE by 36.4% and 41.2%, respectively, and shows strong robustness and predictive accuracy under complex hydrological conditions. This model provides a promising new approach for smart watershed management.
As global climate change intensifies, hydrological cycles are exhibiting increasingly pronounced non-stationary, multi-scale, and highly nonlinear behaviors. Traditional mechanistic models face significant challenges in fully capturing the meteorological–runoff response mechanisms, while deep learning approaches still struggle with long-term dependency modeling, spatial correlations, and sequence decoupling. To address these issues, we propose a hybrid forecasting model, JMD-Gformer, which combines Jump plus AM-FM Mode Decomposition (JMD), sparse directed graph networks, and Transformer-based architectures. In this framework, JMD decomposes the non-stationary runoff time series into jump components (representing abrupt runoff events) and periodic components (capturing seasonal and inter-annual fluctuations), effectively mitigating noise and mode aliasing. Additionally, we construct a sparse directed graph based on meteorology-hydrology nodes to represent the upstream-downstream interactions. The model further incorporates a multi-head self-attention mechanism for long-range temporal dependencies. Experiments conducted on multi-time-scale runoff predictions in the Daliao River Basin demonstrate that, compared to the second-best benchmark model, JMD-Gformer reduces MAPE and RMSE by 36.4% and 41.2%, respectively, and shows strong robustness and predictive accuracy under complex hydrological conditions. This model provides a promising new approach for smart watershed management.
Ye Zili, Zhi Mingqiang, Zhang Wenyu, Li Yuanhe, Shi Yuanzhi, Zhang Chunmin, Zhang Huajun, Huang Wei, Liu Cheng, Yin Hongbin
Available online: June 09, 2026
Abstract:
Taking East Taihu Lake as the research object, this study systematically investigated the physicochemical properties, nutrient distribution and pollutant release characteristics of sediments in historical aquaculture areas and aquatic vegetation zones. The single–factor pollution index method and comprehensive pollution index method were adopted to evaluate sediment pollution, so as to clarify the sediment pollution and release characteristics in the historical aquaculture areas of East Taihu Lake. The results showed that there were significant differences in the physicochemical properties, nutrient contents and distribution of sediments between the historical aquaculture areas and the aquatic vegetation zones. The pH values (7.19 and 7.23, respectively) and moisture contents (65.84% and 54.31%, respectively) of surface sediments at 0–10 cm and 10–20 cm in the aquaculture areas were significantly higher than those in the aquatic vegetation zones (p < 0.05). Moreover, the pH value increased with sediment depth, while the moisture content decreased with depth. The average contents of total nitrogen (TN), total phosphorus (TP) and organic matter (OM) in surface sediments at 0–10 cm in the aquaculture areas were 1610 mg/kg, 665 mg/kg and 4.26%, respectively, which were 1.22, 1.43 and 1.51 times those in the aquatic vegetation zones, and nutrients in the aquaculture areas were mainly accumulated in the surface sediment layer.The average total nitrogen release rate in the aquaculture areas (31.63 mg·m-2·d-1) was much higher than that in the aquatic vegetation zones (-3.99 mg·m-2·d-1), showing a continuous release state, whereas no significant difference was observed in the total phosphorus release rate between the two zones. The concentrations of ammonia nitrogen and ferrous iron in pore water, as well as the release fluxes calculated by Fick"s Law, were significantly higher in the aquaculture areas than in the aquatic vegetation zones (p < 0.05). The average concentration of diffusive gradients in thin films–extractable phosphorus (DGT–P) in the aquaculture areas (0.026 mg/L) was 1.5 times that in the aquatic vegetation zones (0.017 mg/L), indicating a stronger release capacity of labile phosphorus.The sediment pollution assessment revealed that sediment pollution exhibited the characteristics of "vertical decrease and regional differentiation".The proportion of heavily polluted sites for total nitrogen (TN) in the 0–10 cm layer was 17.4%, and that for the comprehensive pollution index (FF) was 35.5%; this proportion for FF decreased to 26.1% in the 10–20 cm layer. The 20–30 cm layer was dominated by light pollution for FF (accounting for 37.4%). The pollution indices of the aquaculture areas were significantly higher than those of the aquatic vegetation zones at all depth layers, and heavily polluted sites were concentrated in the historical aquaculture areas. The results of this study can provide scientific support for the precise control of internal pollution in the aquaculture areas of East Taihu Lake.
Taking East Taihu Lake as the research object, this study systematically investigated the physicochemical properties, nutrient distribution and pollutant release characteristics of sediments in historical aquaculture areas and aquatic vegetation zones. The single–factor pollution index method and comprehensive pollution index method were adopted to evaluate sediment pollution, so as to clarify the sediment pollution and release characteristics in the historical aquaculture areas of East Taihu Lake. The results showed that there were significant differences in the physicochemical properties, nutrient contents and distribution of sediments between the historical aquaculture areas and the aquatic vegetation zones. The pH values (7.19 and 7.23, respectively) and moisture contents (65.84% and 54.31%, respectively) of surface sediments at 0–10 cm and 10–20 cm in the aquaculture areas were significantly higher than those in the aquatic vegetation zones (p < 0.05). Moreover, the pH value increased with sediment depth, while the moisture content decreased with depth. The average contents of total nitrogen (TN), total phosphorus (TP) and organic matter (OM) in surface sediments at 0–10 cm in the aquaculture areas were 1610 mg/kg, 665 mg/kg and 4.26%, respectively, which were 1.22, 1.43 and 1.51 times those in the aquatic vegetation zones, and nutrients in the aquaculture areas were mainly accumulated in the surface sediment layer.The average total nitrogen release rate in the aquaculture areas (31.63 mg·m-2·d-1) was much higher than that in the aquatic vegetation zones (-3.99 mg·m-2·d-1), showing a continuous release state, whereas no significant difference was observed in the total phosphorus release rate between the two zones. The concentrations of ammonia nitrogen and ferrous iron in pore water, as well as the release fluxes calculated by Fick"s Law, were significantly higher in the aquaculture areas than in the aquatic vegetation zones (p < 0.05). The average concentration of diffusive gradients in thin films–extractable phosphorus (DGT–P) in the aquaculture areas (0.026 mg/L) was 1.5 times that in the aquatic vegetation zones (0.017 mg/L), indicating a stronger release capacity of labile phosphorus.The sediment pollution assessment revealed that sediment pollution exhibited the characteristics of "vertical decrease and regional differentiation".The proportion of heavily polluted sites for total nitrogen (TN) in the 0–10 cm layer was 17.4%, and that for the comprehensive pollution index (FF) was 35.5%; this proportion for FF decreased to 26.1% in the 10–20 cm layer. The 20–30 cm layer was dominated by light pollution for FF (accounting for 37.4%). The pollution indices of the aquaculture areas were significantly higher than those of the aquatic vegetation zones at all depth layers, and heavily polluted sites were concentrated in the historical aquaculture areas. The results of this study can provide scientific support for the precise control of internal pollution in the aquaculture areas of East Taihu Lake.
Chen Weijing, Fu Yu, Teng Jiakun, Xie Tian, Lu Xiuming, Yu Hailing, Che Chunguang, Duan Houlang, Yu Xiubo
Available online: June 09, 2026
Abstract:
Hydrology and vegetation are important components of the landscape structure of freshwater wetlands. Changes in the water and sediment regimes of the Yellow River, along with reduced freshwater input, have impacted waterbird diversity in the Shandong Yellow River Delta National Nature Reserve (hereinafter referred to as the "Nature Reserve"). In response, the Nature Reserve has implemented consecutive years of freshwater wetland ecological water supplement projects, regulating the distribution area of open water and shallow water, and improving plant community composition. However, quantitative research on waterbird diversity and its relationship with wetland landscape patterns following this ecological intervention has been lacking. This study utilizes waterbird survey data, Sentinel-2 satellite remote sensing data, and water level monitoring data collected during field investigations in 2023 and 2024. The aim is to elucidate the composition and numerical changes of waterbird communities in the wetland restoration area and to reveal the quantitative relationships between waterbird diversity and the areal extent of key wetland landscape elements. The results showed that a total of 126 waterbird species belonging to 15 families and 7 orders were recorded in the study area. Waterbird species richness and individual abundance exhibited significant monthly fluctuations, with peaks during migration periods in March and November. During migration seasons, ducks and shorebirds dominated in terms of species proportion, while ducks, cranes, and storks dominated in terms of individual abundance. Within the 10,000-mu wetland restoration area of the Nature Reserve, the areas of shallow water (water depth 0-30 cm) and open water were largest. Specifically, the shallow water area was greatest in winter (1888 m2), while the open water area was relatively larger in spring and autumn (2933 m2). The vegetation area exhibited a trend of "expansion in summer, contraction in winter," increasing by 26% in 2024 compared to 2023. The abundance of geese and ducks showed a unimodal relationship with the proportions of both open water area and vegetation area. Goose abundance peaked when the ratio of water area to vegetation area was approximately 2:1 (n = 44, df = 40, p < 0.01, R2 = 0.14; n = 44, df = 40, p < 0.01, R2 = 0.28). Duck abundance peaked when this ratio was approximately 1.5:1 (n = 118, df = 114, p < 0.01, R2 = 0.02; n = 118, df = 114, p < 0.01, R2 = 0.002). The abundance of shorebirds was significantly positively correlated with the proportion of shallow water area (n = 24, df = 22, p < 0.05, R2 = 0.29) but significantly negatively correlated with the proportion of vegetation area (n = 24, df = 22, p < 0.05, R2 = 0.17).
Hydrology and vegetation are important components of the landscape structure of freshwater wetlands. Changes in the water and sediment regimes of the Yellow River, along with reduced freshwater input, have impacted waterbird diversity in the Shandong Yellow River Delta National Nature Reserve (hereinafter referred to as the "Nature Reserve"). In response, the Nature Reserve has implemented consecutive years of freshwater wetland ecological water supplement projects, regulating the distribution area of open water and shallow water, and improving plant community composition. However, quantitative research on waterbird diversity and its relationship with wetland landscape patterns following this ecological intervention has been lacking. This study utilizes waterbird survey data, Sentinel-2 satellite remote sensing data, and water level monitoring data collected during field investigations in 2023 and 2024. The aim is to elucidate the composition and numerical changes of waterbird communities in the wetland restoration area and to reveal the quantitative relationships between waterbird diversity and the areal extent of key wetland landscape elements. The results showed that a total of 126 waterbird species belonging to 15 families and 7 orders were recorded in the study area. Waterbird species richness and individual abundance exhibited significant monthly fluctuations, with peaks during migration periods in March and November. During migration seasons, ducks and shorebirds dominated in terms of species proportion, while ducks, cranes, and storks dominated in terms of individual abundance. Within the 10,000-mu wetland restoration area of the Nature Reserve, the areas of shallow water (water depth 0-30 cm) and open water were largest. Specifically, the shallow water area was greatest in winter (1888 m2), while the open water area was relatively larger in spring and autumn (2933 m2). The vegetation area exhibited a trend of "expansion in summer, contraction in winter," increasing by 26% in 2024 compared to 2023. The abundance of geese and ducks showed a unimodal relationship with the proportions of both open water area and vegetation area. Goose abundance peaked when the ratio of water area to vegetation area was approximately 2:1 (n = 44, df = 40, p < 0.01, R2 = 0.14; n = 44, df = 40, p < 0.01, R2 = 0.28). Duck abundance peaked when this ratio was approximately 1.5:1 (n = 118, df = 114, p < 0.01, R2 = 0.02; n = 118, df = 114, p < 0.01, R2 = 0.002). The abundance of shorebirds was significantly positively correlated with the proportion of shallow water area (n = 24, df = 22, p < 0.05, R2 = 0.29) but significantly negatively correlated with the proportion of vegetation area (n = 24, df = 22, p < 0.05, R2 = 0.17).
Available online: June 08, 2026
Abstract:
To explore the spatiotemporal coupling mechanism of the water network in the Erhai Basin under the combined influence of natural and social drivers, and to reveal the mediating role of topological features between driving factors and water system elements, this study integrates four phases of remote sensing and geographic data within the framework of complex network theory. Nine topological indicators were selected to characterize the structural features of the basin’s water network，to overcome the limitation of traditional regression that it is difficult to simultaneously handle driver collinearity, spatial overflow and mechanism decomposition, this paper constructs a （Partial Least Squares）PLS-（Spatial Durbin Model）SDM-（Mediation effect）MED framework that can handle multi-driver collinearity, simultaneously characterize spatial overflow, and decompose the total effect into direct effects and indirect effects conducted through topological structure, thereby more accurately identifying key intermediate paths. The results show that:(1) From 2001 to 2023, the Erhai water network evolved from a multi-source redundant configuration to a stable state characterized by a clear mainstem and relatively high efficiency.(2) Among a total of 216 paths, 68 significant X-M-Y paths were identified, with mediation efficiencies mainly ranging between 40% and 80%. Betweenness centrality of edges, compactness, global efficiency, and algebraic connectivity were identified as the core mediating indicators.(3) Social factors primarily exerted high-proportion negative effects on hydrological elements through the mediating role of network topology, while natural factors generally displayed moderately strong and stable positive effects, with a few pathways showing structural suppressing effects.The proposed PLS–SDM–Med analytical framework provides a transferable approach for identifying key structural units and risk pathways in plateau lake basins, offering a theoretical basis for zoning control and ecological restoration in the Erhai Basin and other similar highland lake watersheds.
To explore the spatiotemporal coupling mechanism of the water network in the Erhai Basin under the combined influence of natural and social drivers, and to reveal the mediating role of topological features between driving factors and water system elements, this study integrates four phases of remote sensing and geographic data within the framework of complex network theory. Nine topological indicators were selected to characterize the structural features of the basin’s water network，to overcome the limitation of traditional regression that it is difficult to simultaneously handle driver collinearity, spatial overflow and mechanism decomposition, this paper constructs a （Partial Least Squares）PLS-（Spatial Durbin Model）SDM-（Mediation effect）MED framework that can handle multi-driver collinearity, simultaneously characterize spatial overflow, and decompose the total effect into direct effects and indirect effects conducted through topological structure, thereby more accurately identifying key intermediate paths. The results show that:(1) From 2001 to 2023, the Erhai water network evolved from a multi-source redundant configuration to a stable state characterized by a clear mainstem and relatively high efficiency.(2) Among a total of 216 paths, 68 significant X-M-Y paths were identified, with mediation efficiencies mainly ranging between 40% and 80%. Betweenness centrality of edges, compactness, global efficiency, and algebraic connectivity were identified as the core mediating indicators.(3) Social factors primarily exerted high-proportion negative effects on hydrological elements through the mediating role of network topology, while natural factors generally displayed moderately strong and stable positive effects, with a few pathways showing structural suppressing effects.The proposed PLS–SDM–Med analytical framework provides a transferable approach for identifying key structural units and risk pathways in plateau lake basins, offering a theoretical basis for zoning control and ecological restoration in the Erhai Basin and other similar highland lake watersheds.
Available online: June 08, 2026
Abstract:
PME (Phosphate monoesters) are key components of dissolved organic phosphorus, characterized by relatively high abundance and pronounced photoactivity; however, their photochemical dephosphorylation mechanisms in aquatic systems remain to be systematically elucidated. The study systematically investigated the photochemical behavior of the phosphate monoester G6P (Glucose-6-phosphate) by combining experimental investigations with DFT (Density Functional Theory) calculations. The results indicated that the light absorption of G6P is primarily in the 200–290?nm range, with higher photolysis efficiency under shorter-wavelength irradiation. Analysis of energy and electron transfer processes revealed that interactions between G6P and DO (Dissolved Oxygen), DOM (Dissolved Organic Matter), and major anions (e.g., NO3-, HCO3-) do not serve as the main pathways driving its photolysis. Instead, photodegradation relies more on the attack of RIs (Reactive Intermediates) on electron-rich sites, such as the extended region of the glycosyl–phosphate linkage, which triggers molecular destabilization and ultimately leads to IP (Inorganic Phosphate) release. Photolysis experiments further confirmed this mechanism, showing that 3DOM* plays a predominant role in promoting G6P degradation in DOM-containing systems. From an environmental perspective, significant differences were observed in the photolysis of PME between freshwater and seawater systems. The photolysis rate constants of G6P were determined to be (2.00–5.60)?×10-3?h-1 in freshwater and (1.60–3.30)?×10-3?h-1 in seawater. Freshwater systems favor oxidation-dominated pathways with higher thermodynamic driving force, whereas seawater systems, under high salinity and halide-rich conditions, exhibit more pronounced halogen substitution and addition characteristics. Overall, this study demonstrates that the photolysis of PME is co-determined by its molecular structure and ambient aqueous conditions, which collectively govern the pathways and efficiency of its photochemical transformation. These findings provide a new mechanistic perspective for understanding the abiotic mineralization and environmental behavior of DOP (Dissolved Organic Phosphorus) in aquatic systems.
PME (Phosphate monoesters) are key components of dissolved organic phosphorus, characterized by relatively high abundance and pronounced photoactivity; however, their photochemical dephosphorylation mechanisms in aquatic systems remain to be systematically elucidated. The study systematically investigated the photochemical behavior of the phosphate monoester G6P (Glucose-6-phosphate) by combining experimental investigations with DFT (Density Functional Theory) calculations. The results indicated that the light absorption of G6P is primarily in the 200–290?nm range, with higher photolysis efficiency under shorter-wavelength irradiation. Analysis of energy and electron transfer processes revealed that interactions between G6P and DO (Dissolved Oxygen), DOM (Dissolved Organic Matter), and major anions (e.g., NO3-, HCO3-) do not serve as the main pathways driving its photolysis. Instead, photodegradation relies more on the attack of RIs (Reactive Intermediates) on electron-rich sites, such as the extended region of the glycosyl–phosphate linkage, which triggers molecular destabilization and ultimately leads to IP (Inorganic Phosphate) release. Photolysis experiments further confirmed this mechanism, showing that 3DOM* plays a predominant role in promoting G6P degradation in DOM-containing systems. From an environmental perspective, significant differences were observed in the photolysis of PME between freshwater and seawater systems. The photolysis rate constants of G6P were determined to be (2.00–5.60)?×10-3?h-1 in freshwater and (1.60–3.30)?×10-3?h-1 in seawater. Freshwater systems favor oxidation-dominated pathways with higher thermodynamic driving force, whereas seawater systems, under high salinity and halide-rich conditions, exhibit more pronounced halogen substitution and addition characteristics. Overall, this study demonstrates that the photolysis of PME is co-determined by its molecular structure and ambient aqueous conditions, which collectively govern the pathways and efficiency of its photochemical transformation. These findings provide a new mechanistic perspective for understanding the abiotic mineralization and environmental behavior of DOP (Dissolved Organic Phosphorus) in aquatic systems.
Available online: June 08, 2026
Abstract:
The Tianshan Mountains serve as a crucial water resource formation zone in China"s arid northwest region. Understanding the hydrological processes within this area holds significant implications for water resource management in arid zones. The northern slope of the Tianshan Mountains lies at the heart of the Eurasian continent, encompassing primarily the region north of the Tianshan range and the southern edge of the Junggar Basin. It exhibits a typical temperate continental climate. While previous studies have primarily focused on precipitation and groundwater isotopes in arid regions, systematic investigations of river water hydrogen and oxygen stable isotopes across the entire northern slope of the Tianshan Mountains remain scarce. To reveal the stable isotope characteristics of river water on the northern slope of the Tianshan Mountains in the arid northwest region and their implications for the hydrological cycle, this study systematically collected river water samples from major rivers on the northern slope of the Tianshan Mountains between 2022 and 2025. Based on hydrogen and oxygen stable isotope data from 225 samples, it combined isotope analysis with remote sensing technology to elucidate the spatiotemporal variation characteristics of hydrogen and oxygen stable isotope compositions in river water. The study also analyzed the influence of river water physicochemical properties and environmental factors on these isotope compositions. The results indicate:(1) River water hydrogen and oxygen stable isotope compositions exhibit distinct spatiotemporal variation patterns. The ranges of δ2H and δ1?O values for rivers on the northern slope of the Tianshan Mountains were ?117.2‰ to ?46.4‰ and ?17.84‰ to?7.10‰, respectively, with regional averages of ?78.3‰ and ?13.27‰. The temporal variability in the stable hydrogen and oxygen isotope composition is relatively small. Spatially, significant regional differentiation is evident: the western, central, and eastern regions exhibit average δ2H and δ18O values of ?85.8‰,?14.16‰ and ?71.0‰,?12.28‰ and ?81.0‰, ?13.74‰, respectively, forming a spatial distribution pattern with higher values in the central area and lower values in the eastern and western wings.(2) The regional river water line (EL) equation is δ2H = 4.31δ18O? 21.94 (R2=0.72, n=225), with a slope (4.31) significantly lower than that of the local atmospheric precipitation line (slope 7.51) and the global atmospheric precipitation line (slope 8); The hydrogen and oxygen stable isotope compositions of rivers in the western and central regions are primarily dominated by precipitation recharge, while eastern rivers exhibit a strong signal of evaporative fractionation.(3) Hydrogen and oxygen stable isotope compositions in rivers on the northern slope of the Tianshan Mountains are influenced by multiple factors. The physicochemical properties of the river water itself contribute to its isotopic characteristics. Additionally, environmental factors such as precipitation, evapotranspiration, surface temperature, and vegetation cover influence river isotope compositions by regulating local hydrological processes. This study elucidates the spatiotemporal variation patterns of stable hydrogen and oxygen isotopes in river water along the northern slope of the Tianshan Mountains. Through field sampling and remote sensing techniques, it quantitatively identifies the primary factors influencing the stable hydrogen and oxygen isotope composition of regional river water. This research fills a gap in studies using stable hydrogen and oxygen isotopes in river water to indicate hydrological processes across the entire mountain range scale of the northern Tianshan slope, providing isotopic evidence for a deeper understanding of water cycle processes in the Tianshan region"s watersheds.
The Tianshan Mountains serve as a crucial water resource formation zone in China"s arid northwest region. Understanding the hydrological processes within this area holds significant implications for water resource management in arid zones. The northern slope of the Tianshan Mountains lies at the heart of the Eurasian continent, encompassing primarily the region north of the Tianshan range and the southern edge of the Junggar Basin. It exhibits a typical temperate continental climate. While previous studies have primarily focused on precipitation and groundwater isotopes in arid regions, systematic investigations of river water hydrogen and oxygen stable isotopes across the entire northern slope of the Tianshan Mountains remain scarce. To reveal the stable isotope characteristics of river water on the northern slope of the Tianshan Mountains in the arid northwest region and their implications for the hydrological cycle, this study systematically collected river water samples from major rivers on the northern slope of the Tianshan Mountains between 2022 and 2025. Based on hydrogen and oxygen stable isotope data from 225 samples, it combined isotope analysis with remote sensing technology to elucidate the spatiotemporal variation characteristics of hydrogen and oxygen stable isotope compositions in river water. The study also analyzed the influence of river water physicochemical properties and environmental factors on these isotope compositions. The results indicate:(1) River water hydrogen and oxygen stable isotope compositions exhibit distinct spatiotemporal variation patterns. The ranges of δ2H and δ1?O values for rivers on the northern slope of the Tianshan Mountains were ?117.2‰ to ?46.4‰ and ?17.84‰ to?7.10‰, respectively, with regional averages of ?78.3‰ and ?13.27‰. The temporal variability in the stable hydrogen and oxygen isotope composition is relatively small. Spatially, significant regional differentiation is evident: the western, central, and eastern regions exhibit average δ2H and δ18O values of ?85.8‰,?14.16‰ and ?71.0‰,?12.28‰ and ?81.0‰, ?13.74‰, respectively, forming a spatial distribution pattern with higher values in the central area and lower values in the eastern and western wings.(2) The regional river water line (EL) equation is δ2H = 4.31δ18O? 21.94 (R2=0.72, n=225), with a slope (4.31) significantly lower than that of the local atmospheric precipitation line (slope 7.51) and the global atmospheric precipitation line (slope 8); The hydrogen and oxygen stable isotope compositions of rivers in the western and central regions are primarily dominated by precipitation recharge, while eastern rivers exhibit a strong signal of evaporative fractionation.(3) Hydrogen and oxygen stable isotope compositions in rivers on the northern slope of the Tianshan Mountains are influenced by multiple factors. The physicochemical properties of the river water itself contribute to its isotopic characteristics. Additionally, environmental factors such as precipitation, evapotranspiration, surface temperature, and vegetation cover influence river isotope compositions by regulating local hydrological processes. This study elucidates the spatiotemporal variation patterns of stable hydrogen and oxygen isotopes in river water along the northern slope of the Tianshan Mountains. Through field sampling and remote sensing techniques, it quantitatively identifies the primary factors influencing the stable hydrogen and oxygen isotope composition of regional river water. This research fills a gap in studies using stable hydrogen and oxygen isotopes in river water to indicate hydrological processes across the entire mountain range scale of the northern Tianshan slope, providing isotopic evidence for a deeper understanding of water cycle processes in the Tianshan region"s watersheds.
Available online: June 05, 2026
Abstract:
Rivers entering the lake constitute the primary pathways for external nutrient inputs, and variations in nitrogen (N) and phosphorus (P) fluxes directly influence lake eutrophication and the risk of algal blooms. To accurately assess the pollutant export characteristics and driving mechanisms of typical inflow rivers in the Chaohu Basin, this study focuses on the Hangbu River, the largest tributary discharging into Chaohu Lake. Using the period-average flux method, the Load Estimator (LOADEST) model, and the WRTDS model, fluxes and long-term trends were estimated for hydrological and water-quality data from 2019 to 2024 at four stations along the river: Yaojiahe (upstream), Hekou Bridge (midstream), Sanhe Town Bridge (mid-downstream), and Beizhadukou (downstream). The period-average method is computationally simple but produces large errors. In comparison, the LOADEST model performs better in the Chaohu Basin and achieves substantially higher agreement with observed daily fluxes than the WRTDS model. The results show that LOADEST performs best under conditions of continuous discharge records and relatively sparse water-quality measurements, with R2 values of 0.89 to 0.97 and NSE values of 0.84 to 0.98, allowing stable reconstruction of continuous flux series. Based on LOADEST, the estimated total nitrogen (TN) and total phosphorus (TP) fluxes exhibit strong temporal and spatial variability. At the lake-inlet section, the wet season from May to September contributes 68 to 77 percent of annual TN flux and 72 to 81 percent of annual TP flux. A single storm event with 61.8 mm of rainfall can generate as much as 73 percent of the monthly flux, revealing a pronounced pulse-like export pattern. Spatially, TN and TP fluxes increase progressively from upstream to downstream, and the annual fluxes at the Beizhadukou section reach 4.24×106 kg N per year and 2.25×105 kg P per year, which are 10 to 17 times higher than those upstream. Trend decomposition indicates that TN flux into the lake has continued to rise over the past five years, whereas TP flux shows a slight decline, suggesting persistent nitrogen accumulation but a temporary easing of phosphorus export. Overall, flux variations are jointly driven by hydrological processes and human activities. Intense rainfall events amplify the contributions of agricultural and urban pollution to nutrient loading at downstream sections. These findings provide scientific support for external load assessment, pollution control, and algal bloom risk management in the Chaohu Basin under current environmental conditions.
Rivers entering the lake constitute the primary pathways for external nutrient inputs, and variations in nitrogen (N) and phosphorus (P) fluxes directly influence lake eutrophication and the risk of algal blooms. To accurately assess the pollutant export characteristics and driving mechanisms of typical inflow rivers in the Chaohu Basin, this study focuses on the Hangbu River, the largest tributary discharging into Chaohu Lake. Using the period-average flux method, the Load Estimator (LOADEST) model, and the WRTDS model, fluxes and long-term trends were estimated for hydrological and water-quality data from 2019 to 2024 at four stations along the river: Yaojiahe (upstream), Hekou Bridge (midstream), Sanhe Town Bridge (mid-downstream), and Beizhadukou (downstream). The period-average method is computationally simple but produces large errors. In comparison, the LOADEST model performs better in the Chaohu Basin and achieves substantially higher agreement with observed daily fluxes than the WRTDS model. The results show that LOADEST performs best under conditions of continuous discharge records and relatively sparse water-quality measurements, with R2 values of 0.89 to 0.97 and NSE values of 0.84 to 0.98, allowing stable reconstruction of continuous flux series. Based on LOADEST, the estimated total nitrogen (TN) and total phosphorus (TP) fluxes exhibit strong temporal and spatial variability. At the lake-inlet section, the wet season from May to September contributes 68 to 77 percent of annual TN flux and 72 to 81 percent of annual TP flux. A single storm event with 61.8 mm of rainfall can generate as much as 73 percent of the monthly flux, revealing a pronounced pulse-like export pattern. Spatially, TN and TP fluxes increase progressively from upstream to downstream, and the annual fluxes at the Beizhadukou section reach 4.24×106 kg N per year and 2.25×105 kg P per year, which are 10 to 17 times higher than those upstream. Trend decomposition indicates that TN flux into the lake has continued to rise over the past five years, whereas TP flux shows a slight decline, suggesting persistent nitrogen accumulation but a temporary easing of phosphorus export. Overall, flux variations are jointly driven by hydrological processes and human activities. Intense rainfall events amplify the contributions of agricultural and urban pollution to nutrient loading at downstream sections. These findings provide scientific support for external load assessment, pollution control, and algal bloom risk management in the Chaohu Basin under current environmental conditions.
Available online: June 05, 2026
Abstract:
Semi-arid closed lakes are critical nodes where ecological, climate, and human factors intertwine. Their multifunctionality plays an important supporting role in regional sustainable development. This study focuses on the ecological function maintenance of closed lakes in semi-arid regions, with Lake Daihai, a typical inland closed saline lake in the Mongolian Plateau, as the research subject. Given the ongoing deterioration of its water environment, this study conducts a systematic analysis based on continuous monitoring data from 2020 to 2024. Using Principal Component Analysis/Factor Analysis (PCA/FA), five key water quality parameters—dissolved oxygen (DO), chemical oxygen demand (CODCr), total nitrogen (TN), total phosphorus (TP), and salinity (Sal)—were selected from the multidimensional water quality dataset. The spatiotemporal variation patterns of the water environment parameters in Lake Daihai were systematically analyzed, and the Water Quality Index (WQI) was used for quantitative assessment. Pollution source apportionment was carried out using a comparative analysis of the Absolute Principal Component Scores-Multiple Linear Regression (APCS-MLR) and Positive Matrix Factorization (PMF) models. The results show that the PMF model exhibited better performance in pollution source identification. The source apportionment results revealed that the main pollution sources in Lake Daihai are as follows, with their contribution rates: rural domestic pollution (23.5%), planktonic endogenous release (22.5%), livestock farming pollution (20.1%), surface runoff pollution (19.6%), and agricultural cultivation pollution (14.4%). This study quantifies the contribution rates of pollution sources in Lake Daihai, providing a theoretical basis for targeted management and ecological restoration of Daihai and similar lakes in semi-arid regions.
Semi-arid closed lakes are critical nodes where ecological, climate, and human factors intertwine. Their multifunctionality plays an important supporting role in regional sustainable development. This study focuses on the ecological function maintenance of closed lakes in semi-arid regions, with Lake Daihai, a typical inland closed saline lake in the Mongolian Plateau, as the research subject. Given the ongoing deterioration of its water environment, this study conducts a systematic analysis based on continuous monitoring data from 2020 to 2024. Using Principal Component Analysis/Factor Analysis (PCA/FA), five key water quality parameters—dissolved oxygen (DO), chemical oxygen demand (CODCr), total nitrogen (TN), total phosphorus (TP), and salinity (Sal)—were selected from the multidimensional water quality dataset. The spatiotemporal variation patterns of the water environment parameters in Lake Daihai were systematically analyzed, and the Water Quality Index (WQI) was used for quantitative assessment. Pollution source apportionment was carried out using a comparative analysis of the Absolute Principal Component Scores-Multiple Linear Regression (APCS-MLR) and Positive Matrix Factorization (PMF) models. The results show that the PMF model exhibited better performance in pollution source identification. The source apportionment results revealed that the main pollution sources in Lake Daihai are as follows, with their contribution rates: rural domestic pollution (23.5%), planktonic endogenous release (22.5%), livestock farming pollution (20.1%), surface runoff pollution (19.6%), and agricultural cultivation pollution (14.4%). This study quantifies the contribution rates of pollution sources in Lake Daihai, providing a theoretical basis for targeted management and ecological restoration of Daihai and similar lakes in semi-arid regions.
Available online: June 04, 2026
Abstract:
Over the past half-century of evolution in the Yangtze River-Dongting Lake water network, the regulating and storage function of Dongting Lake over the Yangtze River and the Xiang, Zi, Yuan, and Li Rivers in Hunan has gradually shifted from flood retention and sedimentation to flood regulation and sediment replenishment. This transition marks a new phase in the relationship between rivers and lakes, necessitating updated perspectives for their governance and protection. This study, based on comprehensive prototype observation data of the Yangtze River main stream and the Dongting Lake water system, thoroughly analyzes the developmental process, distribution characteristics, and driving factors of sedimentation to sediment replenishment in Dongting Lake. It reveals the macroscopic response of hydrological conditions (flood and dry seasons) in the lake region to changes in sediment deposition status. Results indicate that Dongting Lake has sequentially undergone three developmental stages: the sediment retention weakening phase, the sediment retention stabilization phase, and the sediment replenishment enhancement phase. Sediment deposition progresses from west to east, while sediment replenishment moves from east to west, maintaining the seasonal pattern of deposition during flood periods and replenishment during non-flood periods. Sediment replenishment is primarily dominated by extremely fine particles, which do not contribute to bed formation in the Yangtze River main stream but facilitate the replenishment of nutrient materials. High sediment inflow and weak hydrodynamic conditions are the primary causes of sediment deposition. The sustained decline in sediment concentration of lake inflow, driven by the operation of controlling reservoir groups and soil conservation projects, serves as the core driving factor for sediment replenishment. However, the level of sediment replenishment in the lake region remains low and shows limited potential for further development. Sediment deposition is one of the main factors behind the widespread elevation of the highest water levels in the lake region prior to the impoundment of the Three Gorges Reservoir. The water replenishment regulation of the Three Gorges Reservoir downstream of the dam struggles to mitigate the declining trend of the lowest water levels in the Dongting Lake region. While changes in sediment deposition status will improve flood control conditions in Dongting Lake, the hydrological situation during dry seasons in the lake region is becoming increasingly strained.
Over the past half-century of evolution in the Yangtze River-Dongting Lake water network, the regulating and storage function of Dongting Lake over the Yangtze River and the Xiang, Zi, Yuan, and Li Rivers in Hunan has gradually shifted from flood retention and sedimentation to flood regulation and sediment replenishment. This transition marks a new phase in the relationship between rivers and lakes, necessitating updated perspectives for their governance and protection. This study, based on comprehensive prototype observation data of the Yangtze River main stream and the Dongting Lake water system, thoroughly analyzes the developmental process, distribution characteristics, and driving factors of sedimentation to sediment replenishment in Dongting Lake. It reveals the macroscopic response of hydrological conditions (flood and dry seasons) in the lake region to changes in sediment deposition status. Results indicate that Dongting Lake has sequentially undergone three developmental stages: the sediment retention weakening phase, the sediment retention stabilization phase, and the sediment replenishment enhancement phase. Sediment deposition progresses from west to east, while sediment replenishment moves from east to west, maintaining the seasonal pattern of deposition during flood periods and replenishment during non-flood periods. Sediment replenishment is primarily dominated by extremely fine particles, which do not contribute to bed formation in the Yangtze River main stream but facilitate the replenishment of nutrient materials. High sediment inflow and weak hydrodynamic conditions are the primary causes of sediment deposition. The sustained decline in sediment concentration of lake inflow, driven by the operation of controlling reservoir groups and soil conservation projects, serves as the core driving factor for sediment replenishment. However, the level of sediment replenishment in the lake region remains low and shows limited potential for further development. Sediment deposition is one of the main factors behind the widespread elevation of the highest water levels in the lake region prior to the impoundment of the Three Gorges Reservoir. The water replenishment regulation of the Three Gorges Reservoir downstream of the dam struggles to mitigate the declining trend of the lowest water levels in the Dongting Lake region. While changes in sediment deposition status will improve flood control conditions in Dongting Lake, the hydrological situation during dry seasons in the lake region is becoming increasingly strained.
Available online: June 04, 2026
Abstract:
Runoff simulation and forecasting are essential for watershed flood hazard mitigation and optimal utilization of regional water resources. A key factor affecting these processes is the structural heterogeneity of precipitation inputs. As the primary source of precipitation data derived from ground observations, rain gauges can substantially improve rainfall-runoff modeling accuracy when deployed with appropriate density and spatial distribution. This study constructs a spatio-temporal graph neural network framework that integrates Long Short-Term Memory (LSTM) and Graph Neural Network (GNN) approaches to jointly capture the temporal dynamics of hydrological variables and the spatial topological structure among stations for watershed runoff simulation. Meanwhile, the effects of rain gauge density and spatial distribution on model performance are systematically assessed using multiple mean areal precipitation (MAP) estimation methods. The results revealed that: (1) Rain gauge samples selected through clustering form four density distribution scenarios, representing 100%, 72.22%, 50%, and 27.78% of the full network respectively. Across four distributions, the average Nash-Sutcliffe efficiency (NSE) values exceeded 0.93. The runoff simulation associated with Distribution 3 yielded the best performance (NSE=0.967, mean absolute error MAE=175.5m3/s, relative bias BIAS=0.01, and coefficient of determination R2=0.98) under both high-flow and low-flow conditions; (2) Among all the MAP methods, the clustering weight method produced the most robust results, achieving the highest NSE, relatively low MAE, and BIAS closest to 0. Additionally, Distribution 3 maintained the best overall performance, with the smallest simulation errors and biases. The optimization of the rain gauge network combined with the selection of appropriate MAP approaches can enhance the efficiency and adaptability and simulation accuracy of runoff simulation models, offering a solid scientific foundation for hydrological forecasting.
Runoff simulation and forecasting are essential for watershed flood hazard mitigation and optimal utilization of regional water resources. A key factor affecting these processes is the structural heterogeneity of precipitation inputs. As the primary source of precipitation data derived from ground observations, rain gauges can substantially improve rainfall-runoff modeling accuracy when deployed with appropriate density and spatial distribution. This study constructs a spatio-temporal graph neural network framework that integrates Long Short-Term Memory (LSTM) and Graph Neural Network (GNN) approaches to jointly capture the temporal dynamics of hydrological variables and the spatial topological structure among stations for watershed runoff simulation. Meanwhile, the effects of rain gauge density and spatial distribution on model performance are systematically assessed using multiple mean areal precipitation (MAP) estimation methods. The results revealed that: (1) Rain gauge samples selected through clustering form four density distribution scenarios, representing 100%, 72.22%, 50%, and 27.78% of the full network respectively. Across four distributions, the average Nash-Sutcliffe efficiency (NSE) values exceeded 0.93. The runoff simulation associated with Distribution 3 yielded the best performance (NSE=0.967, mean absolute error MAE=175.5m3/s, relative bias BIAS=0.01, and coefficient of determination R2=0.98) under both high-flow and low-flow conditions; (2) Among all the MAP methods, the clustering weight method produced the most robust results, achieving the highest NSE, relatively low MAE, and BIAS closest to 0. Additionally, Distribution 3 maintained the best overall performance, with the smallest simulation errors and biases. The optimization of the rain gauge network combined with the selection of appropriate MAP approaches can enhance the efficiency and adaptability and simulation accuracy of runoff simulation models, offering a solid scientific foundation for hydrological forecasting.
Available online: June 02, 2026
Abstract:
While there is a wealth of research on the water quality improvement effects of lake ecological restoration projects, a systematic assessment of the dynamic changes in endogenous pollution in sediments and the mechanisms of nitrogen and phosphorus release is lacking. In particular, the seasonal characteristics of nutrient release at the sediment-water interface after ecological restoration of eutrophic lakes in the plateau region remain unclear. This study takes Dapokou, a typical eutrophic water area in the Caohai Lake of Dianchi Lake, as the research object. By comparing the water environment characteristics, sediment nitrogen and phosphorus occurrence forms, and interface release fluxes in the ecological restoration area and the unrestored area during the rainy season (peak growth period of submerged plants) and the dry season (decline period of submerged plants), the study systematically elucidates the spatiotemporal distribution characteristics of nitrogen and phosphorus in the overlying water-sediment system and the seasonal evolution of interface release fluxes in the ecological restoration area. The results show that ecological restoration improved the quality of the overlying water environment, with the water structure exhibiting a transformation from algal to grass-like patterns. During the rainy season, the total nitrogen (TN) and total phosphorus (TP) concentrations in the restored area decreased by 53.9% and 43.2%, respectively, compared to the unrestored area, while transparency (SD) significantly improved, and dissolved oxygen (DO) returned from supersaturation to normal levels. Regarding sediment occurrence, the remediation area exhibited differentiated evolutionary characteristics: total sediment nitrogen (STN) was significantly reduced by about 50% compared to the unremediation area, and convertible nitrogen (TTN) accounted for only 0.01%–0.02% of total nitrogen, with nitrogen mainly in stable form; however, bioavailable phosphorus (BAP) was enriched in the surface layer of the remediation area (reaching 468.72–534.35 mg/kg), forming a high potential releasable phosphorus reservoir. Regarding nitrogen and phosphorus release characteristics, the release flux at the sediment-water interface exhibits a clear seasonal shift: during the rainy season, when submerged plants are thriving, the interface is dominated by net adsorption, with a sediment-phosphorus (SRP) release flux of -1.08 mg/(m2·d). During the dry season, the decomposition of plant remains alters the sediment microenvironment, significantly increasing the interfacial release flux. At some sites, the ammonia nitrogen (NH4+-N) release flux reaches 86.31–91.53 mg/(m2·d), more than seven times that of the unrestored area, and SRP also shifts to a release state. In summary, the Dapokou ecological restoration project demonstrates improved water quality and net adsorption at the interface during the plant growth period, but there is a risk of nitrogen and phosphorus re-release due to remains decomposition during the dry season. Given the significant fluctuations in water levels and the concentrated seasonal decline of vegetation in shallow plateau lakes, submerged plant restoration measures should be combined with management methods such as dry season debris removal, water level regulation, and bottom sediment oxidation maintenance to control the intensity of seasonal endogenous release and provide a scientific basis and engineering reference for the treatment of endogenous pollution in Dianchi Lake and similar plateau lakes.
While there is a wealth of research on the water quality improvement effects of lake ecological restoration projects, a systematic assessment of the dynamic changes in endogenous pollution in sediments and the mechanisms of nitrogen and phosphorus release is lacking. In particular, the seasonal characteristics of nutrient release at the sediment-water interface after ecological restoration of eutrophic lakes in the plateau region remain unclear. This study takes Dapokou, a typical eutrophic water area in the Caohai Lake of Dianchi Lake, as the research object. By comparing the water environment characteristics, sediment nitrogen and phosphorus occurrence forms, and interface release fluxes in the ecological restoration area and the unrestored area during the rainy season (peak growth period of submerged plants) and the dry season (decline period of submerged plants), the study systematically elucidates the spatiotemporal distribution characteristics of nitrogen and phosphorus in the overlying water-sediment system and the seasonal evolution of interface release fluxes in the ecological restoration area. The results show that ecological restoration improved the quality of the overlying water environment, with the water structure exhibiting a transformation from algal to grass-like patterns. During the rainy season, the total nitrogen (TN) and total phosphorus (TP) concentrations in the restored area decreased by 53.9% and 43.2%, respectively, compared to the unrestored area, while transparency (SD) significantly improved, and dissolved oxygen (DO) returned from supersaturation to normal levels. Regarding sediment occurrence, the remediation area exhibited differentiated evolutionary characteristics: total sediment nitrogen (STN) was significantly reduced by about 50% compared to the unremediation area, and convertible nitrogen (TTN) accounted for only 0.01%–0.02% of total nitrogen, with nitrogen mainly in stable form; however, bioavailable phosphorus (BAP) was enriched in the surface layer of the remediation area (reaching 468.72–534.35 mg/kg), forming a high potential releasable phosphorus reservoir. Regarding nitrogen and phosphorus release characteristics, the release flux at the sediment-water interface exhibits a clear seasonal shift: during the rainy season, when submerged plants are thriving, the interface is dominated by net adsorption, with a sediment-phosphorus (SRP) release flux of -1.08 mg/(m2·d). During the dry season, the decomposition of plant remains alters the sediment microenvironment, significantly increasing the interfacial release flux. At some sites, the ammonia nitrogen (NH4+-N) release flux reaches 86.31–91.53 mg/(m2·d), more than seven times that of the unrestored area, and SRP also shifts to a release state. In summary, the Dapokou ecological restoration project demonstrates improved water quality and net adsorption at the interface during the plant growth period, but there is a risk of nitrogen and phosphorus re-release due to remains decomposition during the dry season. Given the significant fluctuations in water levels and the concentrated seasonal decline of vegetation in shallow plateau lakes, submerged plant restoration measures should be combined with management methods such as dry season debris removal, water level regulation, and bottom sediment oxidation maintenance to control the intensity of seasonal endogenous release and provide a scientific basis and engineering reference for the treatment of endogenous pollution in Dianchi Lake and similar plateau lakes.
Yu Haihao, Wang Ligong, Lv Tian, Fan Shufeng, Zuo Zhenjun, Wang Zhong, Yu Dan, Xu Xinwei, Liu Chunhua
Available online: June 02, 2026
Abstract:
As a critical component of freshwater ecosystems, aquatic plants play an essential role in maintaining ecosystem structure, function, and stability. However, under global change scenarios, aquatic plants are facing multiple stressors such as eutrophication, climate warming, emerging pollutants, and biological invasions, leading to a significant decline in aquatic vegetation, particularly submerged macrophytes. Based on systematic research findings over the years from the Liangzi Lake National Field Station for Scientific Observation and Research, Wuhan University, this paper provides a comprehensive review of the major advances in the ecology of aquatic plants and ecosystem functions across individual, population, community, and ecosystem scales. At the individual and population levels, the environmental regulation mechanisms of ecological stoichiometry in aquatic plants were revealed, and the adaptive strategies of clonal integration and functional traits to heterogeneous habitats were elucidated. At the community level, the key regulatory factors of biodiversity-productivity relationships and mechanisms of interspecific interactions were analyzed. In invasion ecology, the mechanisms driving the invasion of exotic aquatic plants under environmental change and biotic interactions were systematically clarified, and the ecological effects of exotic plants on material cycling, epiphytic communities, and pollutant responses were evaluated. In terms of genetic evolution, multi-omics approaches were comprehensively employed to uncover the phylogeographic patterns, local adaptation mechanisms, and invasion potential of aquatic plants. In ecological restoration, long-term in-situ monitoring and restoration practices have verified the effectiveness of submerged vegetation reconstruction in controlling internal nitrogen and phosphorus loading, and new ideas for combined remediation technologies and biological regulation were proposed. These studies not only deepen the theoretical understanding of the relationship between ecological adaptation of aquatic plants and ecosystem functions but also provide important theoretical basis and practical guidance for the conservation, restoration, and sustainable management of freshwater ecosystems.
As a critical component of freshwater ecosystems, aquatic plants play an essential role in maintaining ecosystem structure, function, and stability. However, under global change scenarios, aquatic plants are facing multiple stressors such as eutrophication, climate warming, emerging pollutants, and biological invasions, leading to a significant decline in aquatic vegetation, particularly submerged macrophytes. Based on systematic research findings over the years from the Liangzi Lake National Field Station for Scientific Observation and Research, Wuhan University, this paper provides a comprehensive review of the major advances in the ecology of aquatic plants and ecosystem functions across individual, population, community, and ecosystem scales. At the individual and population levels, the environmental regulation mechanisms of ecological stoichiometry in aquatic plants were revealed, and the adaptive strategies of clonal integration and functional traits to heterogeneous habitats were elucidated. At the community level, the key regulatory factors of biodiversity-productivity relationships and mechanisms of interspecific interactions were analyzed. In invasion ecology, the mechanisms driving the invasion of exotic aquatic plants under environmental change and biotic interactions were systematically clarified, and the ecological effects of exotic plants on material cycling, epiphytic communities, and pollutant responses were evaluated. In terms of genetic evolution, multi-omics approaches were comprehensively employed to uncover the phylogeographic patterns, local adaptation mechanisms, and invasion potential of aquatic plants. In ecological restoration, long-term in-situ monitoring and restoration practices have verified the effectiveness of submerged vegetation reconstruction in controlling internal nitrogen and phosphorus loading, and new ideas for combined remediation technologies and biological regulation were proposed. These studies not only deepen the theoretical understanding of the relationship between ecological adaptation of aquatic plants and ecosystem functions but also provide important theoretical basis and practical guidance for the conservation, restoration, and sustainable management of freshwater ecosystems.
Available online: June 02, 2026
Abstract:
Per- and polyfluoroalkyl substances (PFASs) in peri-urban shallow lakes have attracted increasing scientific attention due to their complex environmental behavior and potential health risks. This study investigated the occurrence, bioaccumulation, and trophic magnification of 15 PFASs in water and tissues (muscle and viscera) of 11 fish species from Luoma Lake (a representative peri-urban shallow lake in eastern China), and conducted a preliminary human health risk assessment associated with fish consumption. Results showed that nine PFASs were detected in surface water (∑PFASs: 58.80~90.59 ng/L), while all 15 target compounds were present in both muscle and visceral tissues (∑PFASs: 166.59~417.65 ng/g dw in muscle; 76.04~897.83 ng/g dw in viscera). PFBA, PFOA, and PFHpA were the predominant congeners in water, muscle, and viscera, respectively. PFASs exhibited pronounced tissue-specific accumulation, with concentrations following the order: kidney > liver > gill > muscle > intestine > brain, indicating preferential enrichment in excretory and metabolic organs. A significant urban-rural gradient was observed: PFASs concentrations in muscle, kidney, liver, and gill of fish from urban zone were significantly higher than those from rural zone, whereas no significant differences were found in brain and intestine. Long-chain PFASs generally displayed higher bioaccumulation factors (BAFs) than short-chain analogues. Trophic transfer analysis revealed that long-chain PFASs underwent significant biomagnification (trophic magnification factor, TMF > 1), whereas short-chain PFASs tended to be biodiluted (TMF < 1). Health risk assessment indicated that current dietary exposure to PFASs via consumption of Luoma Lake fish is within acceptable limits (HR < 1). Nevertheless, potential risks from long-term low-dose exposure and the relatively high cumulative toxicity in rural zones warrant further attention. These findings provide valuable insights into the environmental fate, ecological effects, and health risk management of PFASs in peri-urban shallow lake ecosystems.
Per- and polyfluoroalkyl substances (PFASs) in peri-urban shallow lakes have attracted increasing scientific attention due to their complex environmental behavior and potential health risks. This study investigated the occurrence, bioaccumulation, and trophic magnification of 15 PFASs in water and tissues (muscle and viscera) of 11 fish species from Luoma Lake (a representative peri-urban shallow lake in eastern China), and conducted a preliminary human health risk assessment associated with fish consumption. Results showed that nine PFASs were detected in surface water (∑PFASs: 58.80~90.59 ng/L), while all 15 target compounds were present in both muscle and visceral tissues (∑PFASs: 166.59~417.65 ng/g dw in muscle; 76.04~897.83 ng/g dw in viscera). PFBA, PFOA, and PFHpA were the predominant congeners in water, muscle, and viscera, respectively. PFASs exhibited pronounced tissue-specific accumulation, with concentrations following the order: kidney > liver > gill > muscle > intestine > brain, indicating preferential enrichment in excretory and metabolic organs. A significant urban-rural gradient was observed: PFASs concentrations in muscle, kidney, liver, and gill of fish from urban zone were significantly higher than those from rural zone, whereas no significant differences were found in brain and intestine. Long-chain PFASs generally displayed higher bioaccumulation factors (BAFs) than short-chain analogues. Trophic transfer analysis revealed that long-chain PFASs underwent significant biomagnification (trophic magnification factor, TMF > 1), whereas short-chain PFASs tended to be biodiluted (TMF < 1). Health risk assessment indicated that current dietary exposure to PFASs via consumption of Luoma Lake fish is within acceptable limits (HR < 1). Nevertheless, potential risks from long-term low-dose exposure and the relatively high cumulative toxicity in rural zones warrant further attention. These findings provide valuable insights into the environmental fate, ecological effects, and health risk management of PFASs in peri-urban shallow lake ecosystems.
Zhang Wenting, Zhang Xia, Yan Xingcheng, Feng Tao, Qiao Ruxia, Wang Li, Chen Qiuwen, Zhang Xin, Cao Rui
Available online: June 01, 2026
Abstract:
Dissolved inorganic phosphorus (DIP) is a key limiting nutrient in freshwater ecosystems, and its excessive input poses a serious threat to lake water quality and ecological stability. Previous studies have primarily focused on identifying DIP sources in surface waters such as rivers and lakes, while systematic understanding of the spatiotemporal distribution and source contributions of groundwater DIP remains limited. In this study, the Taihu Basin was selected as a representative case. Groundwater samples were systematically collected during the normal, wet, and dry water period in 2024 to analyze DIP concentrations, hydrochemical characteristics, and phosphate oxygen isotope compositions for source apportionment. The results showed that groundwater levels across the basin generally exhibited a spatial pattern of higher values in the west and lower values in the east, with a central depression zone. During the wet water period, groundwater levels were higher and primarily discharged into Lake Taihu, whereas during the dry water period, groundwater levels declined and the flow direction reversed toward discharge-dominated conditions. Spatially, groundwater DIP concentrations were higher in the central and southern regions of the basin and lower in the western and eastern regions. Temporally, DIP concentrations followed the order wet > normal > dry water period. Hydrochemical analyses indicated that groundwater was mainly affected by agricultural activities and domestic sewage during the wet and normal water period, while industrial activities exerted stronger influence during the dry water period. Source apportionment based on phosphate oxygen isotopes revealed that, during the normal season, the contributions of industrial effluents, domestic sewage, and agricultural wastewater were comparable, accounting for 34%, 31%, and 30%, respectively, while forest runoff contributed the least (5%). During the wet water period, agricultural wastewater became the dominant source, accounting for 37%, whereas domestic sewage and industrial effluents decreased to 28% and 25%, respectively, and forest runoff slightly increased to 10%. In contrast, during the dry water period, the agricultural contribution further increased to 42%, followed by domestic sewage (31%), while forest runoff rose significantly to 18% and industrial effluents declined to 9%. Overall, this study provides the comprehensive characterization of the spatiotemporal patterns and seasonal variations in groundwater DIP sources across the Taihu Basin. The findings offer new insights into identifying dominant groundwater phosphorus sources and provide a scientific basis for developing differentiated strategies for water quality management and eutrophication control in large lake basins.
Dissolved inorganic phosphorus (DIP) is a key limiting nutrient in freshwater ecosystems, and its excessive input poses a serious threat to lake water quality and ecological stability. Previous studies have primarily focused on identifying DIP sources in surface waters such as rivers and lakes, while systematic understanding of the spatiotemporal distribution and source contributions of groundwater DIP remains limited. In this study, the Taihu Basin was selected as a representative case. Groundwater samples were systematically collected during the normal, wet, and dry water period in 2024 to analyze DIP concentrations, hydrochemical characteristics, and phosphate oxygen isotope compositions for source apportionment. The results showed that groundwater levels across the basin generally exhibited a spatial pattern of higher values in the west and lower values in the east, with a central depression zone. During the wet water period, groundwater levels were higher and primarily discharged into Lake Taihu, whereas during the dry water period, groundwater levels declined and the flow direction reversed toward discharge-dominated conditions. Spatially, groundwater DIP concentrations were higher in the central and southern regions of the basin and lower in the western and eastern regions. Temporally, DIP concentrations followed the order wet > normal > dry water period. Hydrochemical analyses indicated that groundwater was mainly affected by agricultural activities and domestic sewage during the wet and normal water period, while industrial activities exerted stronger influence during the dry water period. Source apportionment based on phosphate oxygen isotopes revealed that, during the normal season, the contributions of industrial effluents, domestic sewage, and agricultural wastewater were comparable, accounting for 34%, 31%, and 30%, respectively, while forest runoff contributed the least (5%). During the wet water period, agricultural wastewater became the dominant source, accounting for 37%, whereas domestic sewage and industrial effluents decreased to 28% and 25%, respectively, and forest runoff slightly increased to 10%. In contrast, during the dry water period, the agricultural contribution further increased to 42%, followed by domestic sewage (31%), while forest runoff rose significantly to 18% and industrial effluents declined to 9%. Overall, this study provides the comprehensive characterization of the spatiotemporal patterns and seasonal variations in groundwater DIP sources across the Taihu Basin. The findings offer new insights into identifying dominant groundwater phosphorus sources and provide a scientific basis for developing differentiated strategies for water quality management and eutrophication control in large lake basins.
minjialing, yujinxiang, raorongcheng, huanyi, liufangning, meizhigang, yangying, weilingxia, yinheng, zhangyun, lindanqing, chenyukuan, huaqi, licaigang, quejianglong
Available online: May 28, 2026
Abstract:
To investigate the distribution dynamics of Yangtze finless porpoises (YFPs) in Poyang Lake and its tributaries during the middle of the fishing ban, we conducted ten surveys at different water levels between 2022 and 2025. The results indicate that the YFP population is primarily concentrated in the Laoye Temple-Zhuxi Estuary-Piaotou and Duchang-Piaoshan-Meixizui waters. The high water level period is scattered and widely distributed in the lake area, with less distribution in the waterway connecting the Yangtze River and tributaries; The low water level period is concentrated in the main channel and increases in the distribution of sand pits, the waterway connecting the Yangtze River, and tributary tails. The tributaries Gan River, Xin River, Rao River, Fu River, and Xiu River all have distribution of YFPs. Stable, year-round populations were observed in the Gan River (Yangzizhou) and Xin River (Xiniuwan). Migration activities of YFPs are related to seasons and water levels. During winter/low water periods, they migrate from the lake area to the tail of tributaries, while during summer/high water periods, they migrate from the tail of tributaries to the lake area. And as the low water level continues, the distance of migration towards the tail of the tributary may increase for search of resources and space. The KDE model results indicate that the 50% KDE distribution of the YFPs is mainly continuous in the central part of the lake area during the high water level period, while it is fragmented in the lake area and tributary tails during the low water level period. The 50% KDE area decreases with declining water levels, exhibiting a significant positive linear correlation (R=0.721, P<0.05). The fishing ban has led to an expanded distribution range for the YFPs in Poyang Lake. However, the habitat area has decreased and become fragmented due to the normalization of low water levels which may be an important risk factor for the population. The research results suggest that the protection of YFPs in Poyang Lake should focus on the protection of core home range and the connectivity of ecological corridors under the background of normalized low water levels.
To investigate the distribution dynamics of Yangtze finless porpoises (YFPs) in Poyang Lake and its tributaries during the middle of the fishing ban, we conducted ten surveys at different water levels between 2022 and 2025. The results indicate that the YFP population is primarily concentrated in the Laoye Temple-Zhuxi Estuary-Piaotou and Duchang-Piaoshan-Meixizui waters. The high water level period is scattered and widely distributed in the lake area, with less distribution in the waterway connecting the Yangtze River and tributaries; The low water level period is concentrated in the main channel and increases in the distribution of sand pits, the waterway connecting the Yangtze River, and tributary tails. The tributaries Gan River, Xin River, Rao River, Fu River, and Xiu River all have distribution of YFPs. Stable, year-round populations were observed in the Gan River (Yangzizhou) and Xin River (Xiniuwan). Migration activities of YFPs are related to seasons and water levels. During winter/low water periods, they migrate from the lake area to the tail of tributaries, while during summer/high water periods, they migrate from the tail of tributaries to the lake area. And as the low water level continues, the distance of migration towards the tail of the tributary may increase for search of resources and space. The KDE model results indicate that the 50% KDE distribution of the YFPs is mainly continuous in the central part of the lake area during the high water level period, while it is fragmented in the lake area and tributary tails during the low water level period. The 50% KDE area decreases with declining water levels, exhibiting a significant positive linear correlation (R=0.721, P<0.05). The fishing ban has led to an expanded distribution range for the YFPs in Poyang Lake. However, the habitat area has decreased and become fragmented due to the normalization of low water levels which may be an important risk factor for the population. The research results suggest that the protection of YFPs in Poyang Lake should focus on the protection of core home range and the connectivity of ecological corridors under the background of normalized low water levels.
Available online: May 22, 2026
Abstract:
The Qarhan Salt Lake plays a crucial role in China"s potassium fertilizer production, highlighting the essential relationship of water-salt (Here, the term “water-salt” refers to the coupled mass balance of water (liquid) and potash (solid + dissolved) in the Qarhan playa-lake system)for sustainable resource management and potassium fertilizer supply. This research investigates the complex evolutionary mechanisms governing the water-salt relationship in the mining region, influenced by climate change and human activities. This study utilised a comprehensive set of hydrometeorological data collected over a period of nearly three decades (1990–2024) to identify the evolving trends in the key factors influencing the water-salt relationship in the Qarhan Salt Lake mining area. Pearson correlation analysis was employed to reveal the evolution patterns and driving factors of the water-salt system in this region. The results indicate that over the past two decades (2000-2024), the climate in the mining area has transitioned from "warm and dry" to a "warm and humid". The volume of runoff of the recharged river has increased by more than 20%, accompanied by a temperature increasing of 1.5-2.0 °C. Conversely, a reduction of 18.5% has been noted in evaporation rates. Large-scale resource development activities have adversely affected water replenishment in the mining area, leading to a significant decline in the level of confined brine and a reduction in KCl grade. The implementation of artificial water replenishment and mineral dissolution has been shown to alleviate the severity of these negative impacts. The evolution of water-mineral interactions can be divided into three distinct stages. Initially, there is a transition from a naturally "hydrometeorological-dominated" state to a phase characterized by "combined natural and human influences." This is subsequently followed by a shift to a "human-dominated" trajectory. The key drivers of this transformation include climate warming, brine mining, and artificial water recharge for mineral dissolution. It is clear that brine extraction and artificial water recharge serve as the essential conditions for regulating the water-salt balance. These findings offer a scientific foundation for achieving effective water-salt balance and management in the Qarhan Salt Lake mining area.
The Qarhan Salt Lake plays a crucial role in China"s potassium fertilizer production, highlighting the essential relationship of water-salt (Here, the term “water-salt” refers to the coupled mass balance of water (liquid) and potash (solid + dissolved) in the Qarhan playa-lake system)for sustainable resource management and potassium fertilizer supply. This research investigates the complex evolutionary mechanisms governing the water-salt relationship in the mining region, influenced by climate change and human activities. This study utilised a comprehensive set of hydrometeorological data collected over a period of nearly three decades (1990–2024) to identify the evolving trends in the key factors influencing the water-salt relationship in the Qarhan Salt Lake mining area. Pearson correlation analysis was employed to reveal the evolution patterns and driving factors of the water-salt system in this region. The results indicate that over the past two decades (2000-2024), the climate in the mining area has transitioned from "warm and dry" to a "warm and humid". The volume of runoff of the recharged river has increased by more than 20%, accompanied by a temperature increasing of 1.5-2.0 °C. Conversely, a reduction of 18.5% has been noted in evaporation rates. Large-scale resource development activities have adversely affected water replenishment in the mining area, leading to a significant decline in the level of confined brine and a reduction in KCl grade. The implementation of artificial water replenishment and mineral dissolution has been shown to alleviate the severity of these negative impacts. The evolution of water-mineral interactions can be divided into three distinct stages. Initially, there is a transition from a naturally "hydrometeorological-dominated" state to a phase characterized by "combined natural and human influences." This is subsequently followed by a shift to a "human-dominated" trajectory. The key drivers of this transformation include climate warming, brine mining, and artificial water recharge for mineral dissolution. It is clear that brine extraction and artificial water recharge serve as the essential conditions for regulating the water-salt balance. These findings offer a scientific foundation for achieving effective water-salt balance and management in the Qarhan Salt Lake mining area.
Deng Guoping, Fang Dian, Ding Yuting, Yuan Jia, Zhang Xizhao, Zhou Yanfeng, Xu Dongpo, Tang Fujiang, You Yang
Available online: May 22, 2026
Abstract:
In the 1980s, a fishery transplant was carried out nationwide using the H. nipponensis from the Yalu River system as the source population, which achieved significant economic benefits. However, the genetic diversity of the initial small population established by transplantation has not received due attention due to the subsequent effects of different transplantation behaviors (repeated introduction, mixing of other sources, and unintentional transplantation) and adaptation to the habitat. In this study, 439 individuals were collected from 15 transplanted populations across China’s main production regions (Northeast, North, Northwest and Southwest). Mitochondrial cytochrome c oxidase I (CO I) sequences were used to assess genetic diversity and differentiation. The analysis results showed that a total of 47 haplotypes were detected in 15 populations, Overall haplotype diversity (Hd=0.690) and nucleotide diversity (Pi=0.00290) exhibit species characteristics of high haplotype diversity (Hd) and low nucleotide diversity (Pi). Group Evolutionary Tree, haplotype networks and AMOVA showed that most molecular variance occurred within populations (65.06 %, versus 34.94 % among populations). Populations from Miyun Reservoir (MY) and Panjiakou Reservoir (PJK) in North China formed a separate clade and were highly differentiated from all others (Fst > 0.5), probably reflecting repeated introductions from native Japanese sources. The Dahushi Reservoir (DHS) population showed marked diversity loss, likely attributable to accidental transplantation of a very small founder group. The diversity levels of the four populations in Northeast China, which are connected to the water system of their source areas, are relatively balanced. The populations in Northwest and Southwest China, exhibit moderate to high levels of diversity, which demonstrated the potential adaptation of fish species to the new habitat. Neutrality tests, mismatch distributions and Bayesian skyline plots all indicated a historical population expansion. Based on the current research results, it is recommended to identify the biological management units and core population germplasm resources in China as soon as possible, implement necessary genetic monitoring in a timely manner, and then carry out orderly germplasm use strategies, block based resource management, and fishery production management measures to promote the sustainable and healthy development of the industry.
In the 1980s, a fishery transplant was carried out nationwide using the H. nipponensis from the Yalu River system as the source population, which achieved significant economic benefits. However, the genetic diversity of the initial small population established by transplantation has not received due attention due to the subsequent effects of different transplantation behaviors (repeated introduction, mixing of other sources, and unintentional transplantation) and adaptation to the habitat. In this study, 439 individuals were collected from 15 transplanted populations across China’s main production regions (Northeast, North, Northwest and Southwest). Mitochondrial cytochrome c oxidase I (CO I) sequences were used to assess genetic diversity and differentiation. The analysis results showed that a total of 47 haplotypes were detected in 15 populations, Overall haplotype diversity (Hd=0.690) and nucleotide diversity (Pi=0.00290) exhibit species characteristics of high haplotype diversity (Hd) and low nucleotide diversity (Pi). Group Evolutionary Tree, haplotype networks and AMOVA showed that most molecular variance occurred within populations (65.06 %, versus 34.94 % among populations). Populations from Miyun Reservoir (MY) and Panjiakou Reservoir (PJK) in North China formed a separate clade and were highly differentiated from all others (Fst > 0.5), probably reflecting repeated introductions from native Japanese sources. The Dahushi Reservoir (DHS) population showed marked diversity loss, likely attributable to accidental transplantation of a very small founder group. The diversity levels of the four populations in Northeast China, which are connected to the water system of their source areas, are relatively balanced. The populations in Northwest and Southwest China, exhibit moderate to high levels of diversity, which demonstrated the potential adaptation of fish species to the new habitat. Neutrality tests, mismatch distributions and Bayesian skyline plots all indicated a historical population expansion. Based on the current research results, it is recommended to identify the biological management units and core population germplasm resources in China as soon as possible, implement necessary genetic monitoring in a timely manner, and then carry out orderly germplasm use strategies, block based resource management, and fishery production management measures to promote the sustainable and healthy development of the industry.
Available online: May 20, 2026
Abstract:
: This study investigated the driving mechanisms of methane (CH?) emission flux (FCH?) through controlled laboratory experiments simulating the decomposition process of submerged plant (Potamogeton pectinatus) residues in a eutrophic lake. Four treatment groups were established: a no-plant control (CK), and low (300 g), medium (500 g), and high (1000 g) plant residue addition groups. Constant-temperature incubation was used to simulate environments during both the ice-covered period (0–4°C) and the ice-melt period (10–15°C), with continuous monitoring employed to reveal the dynamics of FCH? and key environmental parameters.The results indicated that plant residue decomposition released dissolved organic carbon (DOC) and total organic carbon (TOC) into the water-sediment system. Their subsequent mineralization produced dissolved inorganic carbon (DIC) and total inorganic carbon (TIC). The decomposition process concurrently consumed dissolved oxygen (DO), causing DO concentrations to rapidly decline below 2 mg/L and forming a strongly reducing anaerobic environment, which significantly increased the abundance of methanogens. During the ice-covered period, FCH? increased significantly with the amount of plant residues added, with the FCH? in the high plant group being 3.7 times that of the control group. This confirms that the synergistic effect of “carbon source input–anoxic environment”drove the increase in FCH? during the ice-covered period.Rising temperatures further accelerated organic matter mineralization and CH? production. During this period, FCH? remained significantly positively correlated with the amount of plant residue added (r = 0.86, p<0.001), indicating that climate warming may amplify the promoting effect of plant input on CH? emissions. In conclusion, the decomposition of plant residues in macrophyte-dominated eutrophic lakes jointly promotes CH? production by supplying organic carbon sources and creating anaerobic conditions, while global climate warming—leading to shorter ice-covered periods and higher temperatures—further exacerbates CH? emissions. This study provides an important theoretical basis for the management of eutrophic lakes under global climate change.
: This study investigated the driving mechanisms of methane (CH?) emission flux (FCH?) through controlled laboratory experiments simulating the decomposition process of submerged plant (Potamogeton pectinatus) residues in a eutrophic lake. Four treatment groups were established: a no-plant control (CK), and low (300 g), medium (500 g), and high (1000 g) plant residue addition groups. Constant-temperature incubation was used to simulate environments during both the ice-covered period (0–4°C) and the ice-melt period (10–15°C), with continuous monitoring employed to reveal the dynamics of FCH? and key environmental parameters.The results indicated that plant residue decomposition released dissolved organic carbon (DOC) and total organic carbon (TOC) into the water-sediment system. Their subsequent mineralization produced dissolved inorganic carbon (DIC) and total inorganic carbon (TIC). The decomposition process concurrently consumed dissolved oxygen (DO), causing DO concentrations to rapidly decline below 2 mg/L and forming a strongly reducing anaerobic environment, which significantly increased the abundance of methanogens. During the ice-covered period, FCH? increased significantly with the amount of plant residues added, with the FCH? in the high plant group being 3.7 times that of the control group. This confirms that the synergistic effect of “carbon source input–anoxic environment”drove the increase in FCH? during the ice-covered period.Rising temperatures further accelerated organic matter mineralization and CH? production. During this period, FCH? remained significantly positively correlated with the amount of plant residue added (r = 0.86, p<0.001), indicating that climate warming may amplify the promoting effect of plant input on CH? emissions. In conclusion, the decomposition of plant residues in macrophyte-dominated eutrophic lakes jointly promotes CH? production by supplying organic carbon sources and creating anaerobic conditions, while global climate warming—leading to shorter ice-covered periods and higher temperatures—further exacerbates CH? emissions. This study provides an important theoretical basis for the management of eutrophic lakes under global climate change.
Available online: May 20, 2026
Abstract:
Arid-zone lakes serve as key indicators of watershed ecological and environmental changes, playing vital hydrological and ecological roles in maintaining regional water-cycle balance and ecosystem stability. This study examines lake dynamics and their climatic responses in the Hunshandake Sandy Land, a climate-sensitive region in northern China characterized by pronounced aridification and ecological fragility. By integrating multi-source datasets including Landsat, Sentinel, Global Surface Water (GSW), and Global Land Analysis and Discovery (GLAD), water extent was mapped applying the water-index method, water classification enhancement approach, and random-forest classification. Changes in water storage were estimated by combining stage-area relationships and volume-area empirical curves. Based on these methods, we quantified monthly and annual changes in lake area (＞0.01 km2) and water storage from 2003 to 2023, while analyzing relevant meteorological factors. Results indicate significant intra-annual seasonality, exhibiting a single-peak trend in lake extent from May to October. At the interannual scale, the lake system has undergone persistent degradation trend over the 21-year record. Total lake area had decreased by 37.17% compared to 2003. The number of lakes declined from 1,198 to 466, primarily driven by losses of small, shallow lakes and widespread drying. Under regional climatic aridity conditions, 8% of formerly permanent water bodies converted to seasonal status, while 86% of seasonal water bodies experienced episodic drying. Net water storage decreased at a rate of -0.005 km3·yr?1, with medium-to-large lakes (≥1km2) accounting for 60% of the storage loss. Climate-driven mechanisms indicate that precipitation, vapor pressure deficit (VPD), and air temperature exhibit spatiotemporal lags of 0-2 months, with precipitation and VPD both peaking at a 1-month lag. VPD emerges as primary negative factor influencing annual and monthly water body area, while precipitation dominates the interannual regulation of seasonal water body area and, jointly governs positively monthly fluctuations with potential evapotranspiration (ET). Temperature indirectly affects lake dynamics by increasing the VPD and evapotranspiration demand. This regional-scale study elucidates the response mechanisms and spatiotemporal heterogeneity of arid-region lakes under climate change, providing data support for adaptive water-resource management in ecologically fragile areas.
Arid-zone lakes serve as key indicators of watershed ecological and environmental changes, playing vital hydrological and ecological roles in maintaining regional water-cycle balance and ecosystem stability. This study examines lake dynamics and their climatic responses in the Hunshandake Sandy Land, a climate-sensitive region in northern China characterized by pronounced aridification and ecological fragility. By integrating multi-source datasets including Landsat, Sentinel, Global Surface Water (GSW), and Global Land Analysis and Discovery (GLAD), water extent was mapped applying the water-index method, water classification enhancement approach, and random-forest classification. Changes in water storage were estimated by combining stage-area relationships and volume-area empirical curves. Based on these methods, we quantified monthly and annual changes in lake area (＞0.01 km2) and water storage from 2003 to 2023, while analyzing relevant meteorological factors. Results indicate significant intra-annual seasonality, exhibiting a single-peak trend in lake extent from May to October. At the interannual scale, the lake system has undergone persistent degradation trend over the 21-year record. Total lake area had decreased by 37.17% compared to 2003. The number of lakes declined from 1,198 to 466, primarily driven by losses of small, shallow lakes and widespread drying. Under regional climatic aridity conditions, 8% of formerly permanent water bodies converted to seasonal status, while 86% of seasonal water bodies experienced episodic drying. Net water storage decreased at a rate of -0.005 km3·yr?1, with medium-to-large lakes (≥1km2) accounting for 60% of the storage loss. Climate-driven mechanisms indicate that precipitation, vapor pressure deficit (VPD), and air temperature exhibit spatiotemporal lags of 0-2 months, with precipitation and VPD both peaking at a 1-month lag. VPD emerges as primary negative factor influencing annual and monthly water body area, while precipitation dominates the interannual regulation of seasonal water body area and, jointly governs positively monthly fluctuations with potential evapotranspiration (ET). Temperature indirectly affects lake dynamics by increasing the VPD and evapotranspiration demand. This regional-scale study elucidates the response mechanisms and spatiotemporal heterogeneity of arid-region lakes under climate change, providing data support for adaptive water-resource management in ecologically fragile areas.
Available online: May 20, 2026
Abstract:
Submerged macrophytes are critical component in ecological restoration of lakes, which harbor epiphytic microbes that play important roles in nutrient cycling and water quality improvement in aquatic ecosystems. However, the responses of planktonic and epiphytic microbial communities to different restoration strategies, as well as the underlying mechanisms, remain largely unknown. To address this gap, we investigated bacterial and microeukaryotic communities in both water column and phyllosphere of Vallisneria natans (V. natans) across three areas of the urban Lake Xuanwu: a near-natural restoration (NR) area, an enclosure restoration (ER) area, and an unrestored (UR) area, to uncover how ecological restoration shapes microbial communities and their potential functions. The results showed that the NR area exhibited higher coverage and greater species richness of submerged macrophytes, along with lower concentrations of total nitrogen (TN), total phosphorus (TP), turbidity (Turb), and chlorophyll a (Chl a). The diversity of both planktonic and phyllosphere microbial communities was significantly higher in the NR area than in the ER and UR areas. The dominant microbial taxa in the phyllosphere of V. natans differed from those in the surrounding water, with obvious compositional differences among the three restoration areas. Variations in microbial community structure were primarily driven by differences in TN, TP, Turb, and Chl a, with bacterial communities being more strongly influenced by environmental factors than microeukaryotic communities. Functional bacterial groups involved in nitrification and nitrate ammonification were selectively enriched in the phyllosphere of V. natans, and the abundance of nitrogen-cycling populations was significantly correlated with ambient nitrogen concentrations in the water. The microbial co-occurrence networks in the NR area displayed greater complexity and stability than those in the ER and UR areas. Compared with the microeukaryotic network, the bacterial network contained more nodes and edges connecting nodes with environmental factors, reflecting a stronger susceptible to environmental influence for the bacterial community. Moreover, based on functional predictions, the key bacterial genera within the phyllosphere network of Vallisneria natans may play important roles in carbon and nitrogen cycling. This study elucidates the mechanisms by which submerged macrophytes regulate microbial community structure, interaction networks, and keystone functional taxa during ecological restoration to improve water quality, thereby providing scientific support for the ecological restoration of eutrophic lakes.
Submerged macrophytes are critical component in ecological restoration of lakes, which harbor epiphytic microbes that play important roles in nutrient cycling and water quality improvement in aquatic ecosystems. However, the responses of planktonic and epiphytic microbial communities to different restoration strategies, as well as the underlying mechanisms, remain largely unknown. To address this gap, we investigated bacterial and microeukaryotic communities in both water column and phyllosphere of Vallisneria natans (V. natans) across three areas of the urban Lake Xuanwu: a near-natural restoration (NR) area, an enclosure restoration (ER) area, and an unrestored (UR) area, to uncover how ecological restoration shapes microbial communities and their potential functions. The results showed that the NR area exhibited higher coverage and greater species richness of submerged macrophytes, along with lower concentrations of total nitrogen (TN), total phosphorus (TP), turbidity (Turb), and chlorophyll a (Chl a). The diversity of both planktonic and phyllosphere microbial communities was significantly higher in the NR area than in the ER and UR areas. The dominant microbial taxa in the phyllosphere of V. natans differed from those in the surrounding water, with obvious compositional differences among the three restoration areas. Variations in microbial community structure were primarily driven by differences in TN, TP, Turb, and Chl a, with bacterial communities being more strongly influenced by environmental factors than microeukaryotic communities. Functional bacterial groups involved in nitrification and nitrate ammonification were selectively enriched in the phyllosphere of V. natans, and the abundance of nitrogen-cycling populations was significantly correlated with ambient nitrogen concentrations in the water. The microbial co-occurrence networks in the NR area displayed greater complexity and stability than those in the ER and UR areas. Compared with the microeukaryotic network, the bacterial network contained more nodes and edges connecting nodes with environmental factors, reflecting a stronger susceptible to environmental influence for the bacterial community. Moreover, based on functional predictions, the key bacterial genera within the phyllosphere network of Vallisneria natans may play important roles in carbon and nitrogen cycling. This study elucidates the mechanisms by which submerged macrophytes regulate microbial community structure, interaction networks, and keystone functional taxa during ecological restoration to improve water quality, thereby providing scientific support for the ecological restoration of eutrophic lakes.
Available online: May 20, 2026
Abstract:
As one of the most advanced ensemble learning technologies, Stacking is an important way to improve the performance of runoff prediction. The existing researches of Stacking-based runoff prediction mostly focus on the accuracy evaluation under few basins and few lead times. Applicability evaluation and influencing factors analysis under multiple basins and multiple lead times remains unexplored. In this study, Support Vector Regression (SVR) and Random Forest (RF) were used as individual learners, and Ridge Regression was used as a meta-learner, and runoff prediction models based on Stacking were constructed. Taking 200 basins in CAMELS dataset as the study area, and taking 1~7 days as the lead times, the accuracy, stability and applicability of Stacking-based runoff prediction were systematically evaluated, and the correlation between the effectiveness of Stacking and the characteristics of basins and the accuracy of individual learners were analyzed. The main results are as follows: (1) The overall accuracy and stability of Stacking are higher than those of the individual learners. (2) Stacking can improve the accuracy of runoff prediction in most basins in the continental United States. The improvement effect is more significant in the basins with heavy precipitation and high temperature, but the effect is relatively limited in the basins with light precipitation and low temperature. (3) Stacking tends to improve prediction accuracy in the basins with low accuracy of the individual learners, but it is difficult to improve the prediction accuracy in the basins with high accuracy of the individual learners. This study can provide a reference for the application of Stacking in runoff prediction.
As one of the most advanced ensemble learning technologies, Stacking is an important way to improve the performance of runoff prediction. The existing researches of Stacking-based runoff prediction mostly focus on the accuracy evaluation under few basins and few lead times. Applicability evaluation and influencing factors analysis under multiple basins and multiple lead times remains unexplored. In this study, Support Vector Regression (SVR) and Random Forest (RF) were used as individual learners, and Ridge Regression was used as a meta-learner, and runoff prediction models based on Stacking were constructed. Taking 200 basins in CAMELS dataset as the study area, and taking 1~7 days as the lead times, the accuracy, stability and applicability of Stacking-based runoff prediction were systematically evaluated, and the correlation between the effectiveness of Stacking and the characteristics of basins and the accuracy of individual learners were analyzed. The main results are as follows: (1) The overall accuracy and stability of Stacking are higher than those of the individual learners. (2) Stacking can improve the accuracy of runoff prediction in most basins in the continental United States. The improvement effect is more significant in the basins with heavy precipitation and high temperature, but the effect is relatively limited in the basins with light precipitation and low temperature. (3) Stacking tends to improve prediction accuracy in the basins with low accuracy of the individual learners, but it is difficult to improve the prediction accuracy in the basins with high accuracy of the individual learners. This study can provide a reference for the application of Stacking in runoff prediction.
luosi, zhoushangrong, zhoujunjie, JinShiyu, quxiao, 葛超, shizhining, wangzexin, zhangzhen, FAMUREW A Janet A
Available online: May 11, 2026
Abstract:
To investigate the trophic niche characteristics of fish in regulated lakes under water level fluctuations, Hongze Lake was selected as the study area. Carbon and nitrogen stable isotope techniques were used to analyze the trophic levels, trophic niche widths, niche overlap, and major food sources of six common benthic fish species—Cyprinus carpio, Pelteobagrus nitidus, Hemibarbus maculatus, Pelteobagrus fulvidraco, Saurogobio dabryi, and Paracanthobrama guichenoti—during the low-water period (July) and the high-water period (November). The results showed that the average trophic levels of all six benthic fish species ranged from 2.43 to 3.65, placing them at mid-trophic levels. However, their δ13C–δ1?N spatial distributions, trophic levels, and resource use patterns differed significantly between species and water-level periods. Distinct trophic niche characteristics were observed for the six fish species across the two periods. Specifically, the trophic niches of S. dabryi and P. guichenoti expanded significantly during the high-water period, indicating trophic niche expansion; the trophic niches of P. nitidus and P. fulvidraco contracted overall, showing trophic niche compression; whereas H. maculatus exhibited relatively stable trophic niche widths between the two periods but demonstrated trophic niche shifts. Niche overlap analysis revealed that trophic niche overlap among benthic fishes was highly asymmetric during the low-water period, suggesting stronger potential interspecific competition, while niche overlap became more symmetric during the high-water period, indicating a reduction in competitive pressure. These findings suggest that water level fluctuations, by altering habitat conditions and food resource patterns, significantly impact the trophic niche structure and interspecific relationships of benthic fishes in Hongze Lake. This study provides valuable insights into fish resource use and coexistence mechanisms under water level fluctuations, and offers scientific guidance for fish resource conservation in regulated lakes.
To investigate the trophic niche characteristics of fish in regulated lakes under water level fluctuations, Hongze Lake was selected as the study area. Carbon and nitrogen stable isotope techniques were used to analyze the trophic levels, trophic niche widths, niche overlap, and major food sources of six common benthic fish species—Cyprinus carpio, Pelteobagrus nitidus, Hemibarbus maculatus, Pelteobagrus fulvidraco, Saurogobio dabryi, and Paracanthobrama guichenoti—during the low-water period (July) and the high-water period (November). The results showed that the average trophic levels of all six benthic fish species ranged from 2.43 to 3.65, placing them at mid-trophic levels. However, their δ13C–δ1?N spatial distributions, trophic levels, and resource use patterns differed significantly between species and water-level periods. Distinct trophic niche characteristics were observed for the six fish species across the two periods. Specifically, the trophic niches of S. dabryi and P. guichenoti expanded significantly during the high-water period, indicating trophic niche expansion; the trophic niches of P. nitidus and P. fulvidraco contracted overall, showing trophic niche compression; whereas H. maculatus exhibited relatively stable trophic niche widths between the two periods but demonstrated trophic niche shifts. Niche overlap analysis revealed that trophic niche overlap among benthic fishes was highly asymmetric during the low-water period, suggesting stronger potential interspecific competition, while niche overlap became more symmetric during the high-water period, indicating a reduction in competitive pressure. These findings suggest that water level fluctuations, by altering habitat conditions and food resource patterns, significantly impact the trophic niche structure and interspecific relationships of benthic fishes in Hongze Lake. This study provides valuable insights into fish resource use and coexistence mechanisms under water level fluctuations, and offers scientific guidance for fish resource conservation in regulated lakes.
Available online: May 11, 2026
Abstract:
To investigate the effect of temperature on the immobilization of phosphorus (P) and arsenic (As) by lanthanum-modified bentonite (LMB) at the sediment-water interface (SWI) and determine the optimal remediation temperature for maximizing its efficacy, laboratory-scale simulation experiments were performed using SWI samples collected from eutrophic shallow lakes. Microelectrode profiling, high-resolution porewater sampling, and inductively coupled plasma mass spectrometry (ICP-MS) were employed to characterize the spatiotemporal dynamics of dissolved oxygen (DO), pH, iron (Fe), manganese (Mn), and dissolved organic matter (DOM) under three controlled temperature conditions (10?℃, 20?℃, and 30?℃). Concurrently, high-precision analytical methods were utilized to quantify the speciation and distribution of dissolved P and As. Results showed that elevated temperatures decreased DO concentrations, increased pH values, and elevated DOM content in the SWI. These changes facilitated the formation of anaerobic conditions, promoting the reductive dissolution of Fe and Mn oxides and thereby enhancing the release of dissolved P and As. The immobilization efficiency of LMB was clearly temperature-dependent, with maximal efficacy observed at 20?℃. At this temperature, the concentrations of dissolved P and As decreased by 85.97% and 41.43%, respectively, on day 7, and remained significantly suppressed on day 50, with reduction rates of 82.10% and 20.35%. Furthermore, LMB application facilitated the transformation of mobile fractions of P and As into more stable chemical forms in the sediment matrix. Specifically, at 20?℃, the proportion of stable P increased from 48.55% to 51.05%, whereas that of stable As rose from 62.20% to 68.92%. This study demonstrates that the effectiveness of LMB in mitigating the release of P and As at the SWI is strongly temperature-dependent. The optimal restoration temperature of 20?℃ identified by the study can be applied to address endogenous pollution in shallow lakes of temperate and subtropical regions during the spring and autumn seasons when water temperatures are suitable. Keyword: Temperature; lanthanum-modified bentonite; sediment-water interface; phosphorus; arsenic
To investigate the effect of temperature on the immobilization of phosphorus (P) and arsenic (As) by lanthanum-modified bentonite (LMB) at the sediment-water interface (SWI) and determine the optimal remediation temperature for maximizing its efficacy, laboratory-scale simulation experiments were performed using SWI samples collected from eutrophic shallow lakes. Microelectrode profiling, high-resolution porewater sampling, and inductively coupled plasma mass spectrometry (ICP-MS) were employed to characterize the spatiotemporal dynamics of dissolved oxygen (DO), pH, iron (Fe), manganese (Mn), and dissolved organic matter (DOM) under three controlled temperature conditions (10?℃, 20?℃, and 30?℃). Concurrently, high-precision analytical methods were utilized to quantify the speciation and distribution of dissolved P and As. Results showed that elevated temperatures decreased DO concentrations, increased pH values, and elevated DOM content in the SWI. These changes facilitated the formation of anaerobic conditions, promoting the reductive dissolution of Fe and Mn oxides and thereby enhancing the release of dissolved P and As. The immobilization efficiency of LMB was clearly temperature-dependent, with maximal efficacy observed at 20?℃. At this temperature, the concentrations of dissolved P and As decreased by 85.97% and 41.43%, respectively, on day 7, and remained significantly suppressed on day 50, with reduction rates of 82.10% and 20.35%. Furthermore, LMB application facilitated the transformation of mobile fractions of P and As into more stable chemical forms in the sediment matrix. Specifically, at 20?℃, the proportion of stable P increased from 48.55% to 51.05%, whereas that of stable As rose from 62.20% to 68.92%. This study demonstrates that the effectiveness of LMB in mitigating the release of P and As at the SWI is strongly temperature-dependent. The optimal restoration temperature of 20?℃ identified by the study can be applied to address endogenous pollution in shallow lakes of temperate and subtropical regions during the spring and autumn seasons when water temperatures are suitable. Keyword: Temperature; lanthanum-modified bentonite; sediment-water interface; phosphorus; arsenic
Available online: May 11, 2026
Abstract:
Microcystis, the most frequently observed genus among cyanobacterial blooms, exhibits significant morphological diversity and pronounced spatio-tempo variation. However, the seasonal distribution patterns of its distinct morphological characteristics remain unclear. This study systematically analyzed the morphological features, spatio-temporal distribution patterns, and coupling relationships with environmental factors (temperature, nutrients, etc.) of Microcystis in Chaohu Lake from 2022 to 2024. Results indicate: Significant differences exist among Microcystis species in colony size and single-cell diameter. M. panniformis and M. aeruginosa exhibit the largest colony sizes, significantly exceeding those of M. flos-aquae and M. botrys. M. wesenbergii possesses the largest cell diameter, significantly exceeding M. botrys, M. aeruginosa, and M. viridis, while M. flos-aquae and M. ichthyoblabe exhibit the smallest diameters. These phenomenon exhibited distinct differences in response to nutrients (nitrogen, phosphorus) and temperature. Nitrogen and phosphorus were key nutrients influencing Microcystis population size and cell diameter, with significant differences in the distribution proportions of different species across total nitrogen and temperature ranges. During the cold season, M. viridis and M. pseudofilamentosa exhibited higher frequencies. As water temperatures rose into the warm season, the community shifted toward higher frequencies of M. wesenbergii, M. novacekii, and M. aeruginosa. In the hot season, M. botrys and M. smithii became the most frequent species. Correlation analysis and regression models further revealed the regulatory effects of environmental factors on Microcystis cell diameter. Temperature and phosphorus show significant correlations (p<0.05) with cell diameter in most species. This study aims to provide scientific basis for understanding the ecological adaptation mechanisms of Microcystis in Chaohu Lake and for managing cyanobacteria in eutrophic lakes.
Microcystis, the most frequently observed genus among cyanobacterial blooms, exhibits significant morphological diversity and pronounced spatio-tempo variation. However, the seasonal distribution patterns of its distinct morphological characteristics remain unclear. This study systematically analyzed the morphological features, spatio-temporal distribution patterns, and coupling relationships with environmental factors (temperature, nutrients, etc.) of Microcystis in Chaohu Lake from 2022 to 2024. Results indicate: Significant differences exist among Microcystis species in colony size and single-cell diameter. M. panniformis and M. aeruginosa exhibit the largest colony sizes, significantly exceeding those of M. flos-aquae and M. botrys. M. wesenbergii possesses the largest cell diameter, significantly exceeding M. botrys, M. aeruginosa, and M. viridis, while M. flos-aquae and M. ichthyoblabe exhibit the smallest diameters. These phenomenon exhibited distinct differences in response to nutrients (nitrogen, phosphorus) and temperature. Nitrogen and phosphorus were key nutrients influencing Microcystis population size and cell diameter, with significant differences in the distribution proportions of different species across total nitrogen and temperature ranges. During the cold season, M. viridis and M. pseudofilamentosa exhibited higher frequencies. As water temperatures rose into the warm season, the community shifted toward higher frequencies of M. wesenbergii, M. novacekii, and M. aeruginosa. In the hot season, M. botrys and M. smithii became the most frequent species. Correlation analysis and regression models further revealed the regulatory effects of environmental factors on Microcystis cell diameter. Temperature and phosphorus show significant correlations (p<0.05) with cell diameter in most species. This study aims to provide scientific basis for understanding the ecological adaptation mechanisms of Microcystis in Chaohu Lake and for managing cyanobacteria in eutrophic lakes.
Available online: May 09, 2026
Abstract:
To elucidate the trophic ecological characteristics of the fish community in the Jiangjin section of the National Nature Reserve for Rare and Endemic Fishes in the Upper Yangtze River, this study analyzed 246 individuals across 42 fish species using stable isotope analysis (SIA) of carbon (δ13C) and nitrogen (δ1?N) during the flood and dry seasons of 2024. The results revealed that: (1) At the fish community level, the δ13C values ranged from -28.76‰ to -19.05‰, showing no significant difference between the flood and dry seasons; meanwhile, the δ1?N values ranged from 3.73‰ to 13.01‰, exhibiting significant seasonal differences and reflecting clear trophic differentiation. (2) The trophic level (TL) of the fish community ranged from 1.17 to 3.82, with a mean value of 2.37 ± 0.45, illustrating multi-level trophic relationships. (3) Significant seasonal hydrological differences were observed in the community trophic structure, with overall δ1?N values and the trophic levels of major feeding guilds being significantly higher in the dry season than in the flood season(P<0.05). (4) The community trophic niche width, measured by the Standard Ellipse Area (SEAc), was significantly larger in the flood season than in the dry season, indicating seasonal hydrological differences in food resource utilization patterns. This study provides a critical perspective for understanding the food web structure, seasonal hydrological dynamics, and resource utilization strategies of the fish community in this protected area, thereby offering a scientific basis for fish biodiversity conservation and ecosystem management in the region.
To elucidate the trophic ecological characteristics of the fish community in the Jiangjin section of the National Nature Reserve for Rare and Endemic Fishes in the Upper Yangtze River, this study analyzed 246 individuals across 42 fish species using stable isotope analysis (SIA) of carbon (δ13C) and nitrogen (δ1?N) during the flood and dry seasons of 2024. The results revealed that: (1) At the fish community level, the δ13C values ranged from -28.76‰ to -19.05‰, showing no significant difference between the flood and dry seasons; meanwhile, the δ1?N values ranged from 3.73‰ to 13.01‰, exhibiting significant seasonal differences and reflecting clear trophic differentiation. (2) The trophic level (TL) of the fish community ranged from 1.17 to 3.82, with a mean value of 2.37 ± 0.45, illustrating multi-level trophic relationships. (3) Significant seasonal hydrological differences were observed in the community trophic structure, with overall δ1?N values and the trophic levels of major feeding guilds being significantly higher in the dry season than in the flood season(P<0.05). (4) The community trophic niche width, measured by the Standard Ellipse Area (SEAc), was significantly larger in the flood season than in the dry season, indicating seasonal hydrological differences in food resource utilization patterns. This study provides a critical perspective for understanding the food web structure, seasonal hydrological dynamics, and resource utilization strategies of the fish community in this protected area, thereby offering a scientific basis for fish biodiversity conservation and ecosystem management in the region.
Available online: May 09, 2026
Abstract:
With climate change, the increasing frequency and intensity of extreme climate events have intensified the outbreak and expansion of cyanobacterial blooms in shallow eutrophic lakes, posing severe threats to the security and water supply safety of lake ecosystems. However, how extreme climate events drive the long-term dynamics of cyanobacterial blooms, as well as the dominant factors and underlying mechanisms, remain unclear. Taking Lake Hongze as a case study, Mann-Kendall trend analysis based on 64 years of meteorological observations revealed a significant warming trend in extreme temperature indices. Since 1991, the total duration and frequency of extreme heat events has increased by approximately 5.33 days and 2 events per decade, respectively. Meanwhile, the Simple Daily Intensity Index (SDII) and the annual total precipitation from very wet days (R95p) have increased by 0.38 mm d-1and 15.18 mm per decade, respectively. Based on remote-sensing observations from 2003 to 2020, the bloom occurrence rate in Lake Hongze has increased by 1.15%, while the maximum bloom extent has expanded by 154.69 km². The bloom onset has advanced by 24.56 days, and the potential bloom duration has extended by an average of 27.20 days. Further attribution analysis using the SHAP method indicated that the bloom occurrence rate and the maximum bloom extent are the cyanobacterial bloom metrics most sensitive to extreme climate events, with the mean intensity of extreme heat events playing a dominant role. The continued intensification of extreme heat events is expected to further advance the bloom onset and expand the bloom extent. Notably, when temperatures exceed a certain threshold, algal growth may be inhibited due to thermal stress, suggesting a dual “promoting-inhibiting” effect of extreme heat events on cyanobacterial bloom dynamics. This study elucidates the response mechanisms and threshold behaviors of cyanobacterial blooms under extreme climate forcing, providing a theoretical basis and scientific support for the early warning of bloom risks and adaptive watershed management.
With climate change, the increasing frequency and intensity of extreme climate events have intensified the outbreak and expansion of cyanobacterial blooms in shallow eutrophic lakes, posing severe threats to the security and water supply safety of lake ecosystems. However, how extreme climate events drive the long-term dynamics of cyanobacterial blooms, as well as the dominant factors and underlying mechanisms, remain unclear. Taking Lake Hongze as a case study, Mann-Kendall trend analysis based on 64 years of meteorological observations revealed a significant warming trend in extreme temperature indices. Since 1991, the total duration and frequency of extreme heat events has increased by approximately 5.33 days and 2 events per decade, respectively. Meanwhile, the Simple Daily Intensity Index (SDII) and the annual total precipitation from very wet days (R95p) have increased by 0.38 mm d-1and 15.18 mm per decade, respectively. Based on remote-sensing observations from 2003 to 2020, the bloom occurrence rate in Lake Hongze has increased by 1.15%, while the maximum bloom extent has expanded by 154.69 km². The bloom onset has advanced by 24.56 days, and the potential bloom duration has extended by an average of 27.20 days. Further attribution analysis using the SHAP method indicated that the bloom occurrence rate and the maximum bloom extent are the cyanobacterial bloom metrics most sensitive to extreme climate events, with the mean intensity of extreme heat events playing a dominant role. The continued intensification of extreme heat events is expected to further advance the bloom onset and expand the bloom extent. Notably, when temperatures exceed a certain threshold, algal growth may be inhibited due to thermal stress, suggesting a dual “promoting-inhibiting” effect of extreme heat events on cyanobacterial bloom dynamics. This study elucidates the response mechanisms and threshold behaviors of cyanobacterial blooms under extreme climate forcing, providing a theoretical basis and scientific support for the early warning of bloom risks and adaptive watershed management.
Available online: May 09, 2026
Abstract:
Lake ecosystems in cold and arid regions are highly sensitive to climate change and anthropogenic disturbances, with phytoplankton community dynamics serving as a key indicator of aquatic ecological changes. Hulun Lake, a typical shallow lake in the arid and semi-arid region of northern China, has experienced significant alterations in its hydrological cycle and pollution patterns following the implementation of the "River Water Diversion to Lake" project, leading to eutrophication. Against this backdrop, investigating the assembly mechanisms of its phytoplankton community and identifying the key environmental drivers are crucial for lake ecological restoration and algal bloom prevention. This study conducted systematic ecological surveys at 26 sampling sites in the main body of Hulun Lake and its major inflow rivers during spring and summer of 2024 and 2025. The aim was to analyze the seasonal succession patterns of the phytoplankton community, its taxonomic beta diversity characteristics, and its coupling relationship with environmental factors. The results showed that: The phytoplankton community structure exhibited significant seasonal succession. Bacillariophyta dominated in spring, with Cyclotella menaquinone as the key dominant species, while the community shifted to absolute dominance by Cyanobacteria in summer, led by Microcystis aeruginosa and Anabaenopsis oscillarioides. Although species richness was higher in summer, the Shannon-Wiener diversity index was significantly lower than in spring. Canonical Correspondence Analysis (CCA) indicated that the key environmental drivers of community succession differed between seasons. The spring community was primarily influenced by Total Phosphorus (TP), Turbidity (Turb), and Chemical Oxygen Demand (BOD<sub>5</sub>), whereas the summer community was mainly driven by Water Temperature (WT), Total Nitrogen (TN), Five-day Biochemical Oxygen Demand (BOD<sub>5</sub>), and Chlorophyll-a (Chl-a). Decomposition of taxonomic beta diversity revealed that the total β-diversity between seasons and across years was primarily driven by the turnover component, with a limited contribution from the nestedness component. This indicates that species replacement is the core process structuring the phytoplankton community in Hulun Lake, reflecting strong environmental filtering and habitat heterogeneity. This study, from the dual perspectives of species composition and community assembly mechanisms, reveals that environmental filtering is the core driving force shaping the seasonal dynamics of the phytoplankton community in Hulun Lake. The research findings not only identify key regulatory factors in the eutrophication process of Hulun Lake but also provide important scientific evidence and a case study for the aquatic ecological health assessment, cyanobacterial bloom early warning, and ecological restoration practices for Hulun Lake and similar lakes in cold and arid regions of northern China.
Lake ecosystems in cold and arid regions are highly sensitive to climate change and anthropogenic disturbances, with phytoplankton community dynamics serving as a key indicator of aquatic ecological changes. Hulun Lake, a typical shallow lake in the arid and semi-arid region of northern China, has experienced significant alterations in its hydrological cycle and pollution patterns following the implementation of the "River Water Diversion to Lake" project, leading to eutrophication. Against this backdrop, investigating the assembly mechanisms of its phytoplankton community and identifying the key environmental drivers are crucial for lake ecological restoration and algal bloom prevention. This study conducted systematic ecological surveys at 26 sampling sites in the main body of Hulun Lake and its major inflow rivers during spring and summer of 2024 and 2025. The aim was to analyze the seasonal succession patterns of the phytoplankton community, its taxonomic beta diversity characteristics, and its coupling relationship with environmental factors. The results showed that: The phytoplankton community structure exhibited significant seasonal succession. Bacillariophyta dominated in spring, with Cyclotella menaquinone as the key dominant species, while the community shifted to absolute dominance by Cyanobacteria in summer, led by Microcystis aeruginosa and Anabaenopsis oscillarioides. Although species richness was higher in summer, the Shannon-Wiener diversity index was significantly lower than in spring. Canonical Correspondence Analysis (CCA) indicated that the key environmental drivers of community succession differed between seasons. The spring community was primarily influenced by Total Phosphorus (TP), Turbidity (Turb), and Chemical Oxygen Demand (BOD<sub>5</sub>), whereas the summer community was mainly driven by Water Temperature (WT), Total Nitrogen (TN), Five-day Biochemical Oxygen Demand (BOD<sub>5</sub>), and Chlorophyll-a (Chl-a). Decomposition of taxonomic beta diversity revealed that the total β-diversity between seasons and across years was primarily driven by the turnover component, with a limited contribution from the nestedness component. This indicates that species replacement is the core process structuring the phytoplankton community in Hulun Lake, reflecting strong environmental filtering and habitat heterogeneity. This study, from the dual perspectives of species composition and community assembly mechanisms, reveals that environmental filtering is the core driving force shaping the seasonal dynamics of the phytoplankton community in Hulun Lake. The research findings not only identify key regulatory factors in the eutrophication process of Hulun Lake but also provide important scientific evidence and a case study for the aquatic ecological health assessment, cyanobacterial bloom early warning, and ecological restoration practices for Hulun Lake and similar lakes in cold and arid regions of northern China.
Available online: May 08, 2026
Abstract:
To address the limitations of data-driven model, which lack physical constraints, and to enable rapid prediction of reservoir thermal structure under future non-stationary climate scenarios, this study proposes a hybrid framework that integrates physical mechanisms with data-driven modeling for predicting reservoir water temperature profiles. Utilizing observed data from the Sanbanxi Reservoir (2007-2016), a one-dimensional hydrodynamic-water temperature model (GLM), a Random Forest-Bidirectional Long Short-Term Memory (RF-BILSTM) machine learning model, and Global Climate Models (GCMs), we reconstructed the historical thermal structure of the reservoir and projected its evolution under future climate scenarios from 2023 to 2100. The results indicate that: (1) A physically constrained training data set generated by combining the GLM model with measured data effectively mitigates spurious correlations inherent in purely data-driven approaches. The RF-BILSTM prediction framework achieved high simulation accuracy, with R2> 0.9. (2) Projections from GCMs show a significant increasing trend in future air temperature at the Sanbanxi Reservoir (p < 0.01). The temperature increase under the SSP5-8.5 scenario is substantially greater than under SSP2-4.5, while precipitation also exhibits a significant upward trend. (3) By 2100, the average water temperature in the reservoir is projected to rise by 0.39 ℃ and 0.87 ℃ under the SSP2-4.5 and SSP5-8.5 scenarios, respectively, showing pronounced vertical differentiation. Surface warming is more significant, with projected increases of 0.94℃ and 2.04℃, respectively. The annual mean surface-bottom temperature difference is expected to increase by 1.32℃ and 1.55℃, with the maximum vertical difference occurring in August. Annual water column stability (Schmidt stability, St) is projected to increase by 643.41 J/m2(+7.85%) and 1829.47 J/m2(+22.31%), respectively, indicating intensified thermal stratification. This could elevate the risks of surface algal blooms and nutrient stratification enrichment, while also advancing the spawning timing of downstream fish. This study presents a novel approach that deeply integrates physical mechanisms with data-driven techniques, providing technical support for reservoir water temperature management.
To address the limitations of data-driven model, which lack physical constraints, and to enable rapid prediction of reservoir thermal structure under future non-stationary climate scenarios, this study proposes a hybrid framework that integrates physical mechanisms with data-driven modeling for predicting reservoir water temperature profiles. Utilizing observed data from the Sanbanxi Reservoir (2007-2016), a one-dimensional hydrodynamic-water temperature model (GLM), a Random Forest-Bidirectional Long Short-Term Memory (RF-BILSTM) machine learning model, and Global Climate Models (GCMs), we reconstructed the historical thermal structure of the reservoir and projected its evolution under future climate scenarios from 2023 to 2100. The results indicate that: (1) A physically constrained training data set generated by combining the GLM model with measured data effectively mitigates spurious correlations inherent in purely data-driven approaches. The RF-BILSTM prediction framework achieved high simulation accuracy, with R2> 0.9. (2) Projections from GCMs show a significant increasing trend in future air temperature at the Sanbanxi Reservoir (p < 0.01). The temperature increase under the SSP5-8.5 scenario is substantially greater than under SSP2-4.5, while precipitation also exhibits a significant upward trend. (3) By 2100, the average water temperature in the reservoir is projected to rise by 0.39 ℃ and 0.87 ℃ under the SSP2-4.5 and SSP5-8.5 scenarios, respectively, showing pronounced vertical differentiation. Surface warming is more significant, with projected increases of 0.94℃ and 2.04℃, respectively. The annual mean surface-bottom temperature difference is expected to increase by 1.32℃ and 1.55℃, with the maximum vertical difference occurring in August. Annual water column stability (Schmidt stability, St) is projected to increase by 643.41 J/m2(+7.85%) and 1829.47 J/m2(+22.31%), respectively, indicating intensified thermal stratification. This could elevate the risks of surface algal blooms and nutrient stratification enrichment, while also advancing the spawning timing of downstream fish. This study presents a novel approach that deeply integrates physical mechanisms with data-driven techniques, providing technical support for reservoir water temperature management.
Available online: May 08, 2026
Abstract:
Exploring the temporal variation characteristics of phytoplankton community structure is of great significance for understanding the evolution of aquatic ecological environment; The automatic monitoring of phytoplankton communities provides fundamental data for revealing the multi-scale changes in phytoplankton community structure. However, the multi periodicity of high-frequency monitoring data also poses challenges to traditional time series analysis methods. This study takes the Jiangdong Reservoir in Beixi, Jiulong River as a case study, and obtains hourly automatic monitoring data of the biomass of four groups of green algae, blue-green algae, diatoms, and cryptoalgae from 2017 to 2022. Using Multiple Seasonal-Trend decomposition using LOESS, the biomass of each group is decomposed into four components: trend, annual period, daily period, and residual. The multi time scale variation characteristics of community structure are analyzed. The results showed that: (1) The biomass of the green algae group rapidly increased from 2020 and reached its peak in 2021, becoming the dominant group; The overall trend of other groups is declining. (2) The seasonal fluctuations of various groups are relatively stable, with cryptic algae having the largest amplitude, followed by green algae and blue-green algae, and diatoms having the smallest amplitude. (3) All types of groups have stable diurnal rhythms, reaching their peak before 12-16 pm, with green algae showing the largest amplitude and blue-green algae showing the smoothest changes. (4) Seasonal cycles and long-term trends jointly explain the main part of community abundance variation, while the contribution of daily cycles is relatively small. The research results indicate that the changes in green algae and diatom groups are driven by both multi-year background and seasonal factors, while the fluctuations in blue-green algae and cryptoalgae groups are more dependent on seasonal temperature light cycles. This study reveals the dominant substitution and niche segregation phenomena of phytoplankton at multiple scales including interannual, seasonal, and diurnal, which can provide scientific basis for early warning of harmful algal blooms and management of aquatic ecosystems.
Exploring the temporal variation characteristics of phytoplankton community structure is of great significance for understanding the evolution of aquatic ecological environment; The automatic monitoring of phytoplankton communities provides fundamental data for revealing the multi-scale changes in phytoplankton community structure. However, the multi periodicity of high-frequency monitoring data also poses challenges to traditional time series analysis methods. This study takes the Jiangdong Reservoir in Beixi, Jiulong River as a case study, and obtains hourly automatic monitoring data of the biomass of four groups of green algae, blue-green algae, diatoms, and cryptoalgae from 2017 to 2022. Using Multiple Seasonal-Trend decomposition using LOESS, the biomass of each group is decomposed into four components: trend, annual period, daily period, and residual. The multi time scale variation characteristics of community structure are analyzed. The results showed that: (1) The biomass of the green algae group rapidly increased from 2020 and reached its peak in 2021, becoming the dominant group; The overall trend of other groups is declining. (2) The seasonal fluctuations of various groups are relatively stable, with cryptic algae having the largest amplitude, followed by green algae and blue-green algae, and diatoms having the smallest amplitude. (3) All types of groups have stable diurnal rhythms, reaching their peak before 12-16 pm, with green algae showing the largest amplitude and blue-green algae showing the smoothest changes. (4) Seasonal cycles and long-term trends jointly explain the main part of community abundance variation, while the contribution of daily cycles is relatively small. The research results indicate that the changes in green algae and diatom groups are driven by both multi-year background and seasonal factors, while the fluctuations in blue-green algae and cryptoalgae groups are more dependent on seasonal temperature light cycles. This study reveals the dominant substitution and niche segregation phenomena of phytoplankton at multiple scales including interannual, seasonal, and diurnal, which can provide scientific basis for early warning of harmful algal blooms and management of aquatic ecosystems.
Available online: May 07, 2026
Abstract:
To understand the changes in fish community structure and diversity in the Zhenjiang section of the Yangtze River since the implementation of the ten-year fishing ban, this study conducted surveys once during the fish breeding period (April–July) and once during the fattening period (September–November) each year from 2021 to 2024. Over the four-year period, a total of 792 net hauls were conducted in the Zhenjiang section, collecting 3,908 fish weighing 575.62?kg. A total of 66 fish species were identified, belonging to 9 orders, 16 families, and 47 genera. During the study period, the fish assemblage in the Zhenjiang reach of the Yangtze River was dominated by omnivorous (carnivorous) species, freshwater resident species, and benthic fish, accounting for 40.91% (40.91%), 69.70%, and 43.94% of the total species, respectively. The dominant species were Parabramis pekinensis, Hemiculter bleekeri, and Saurogobio dabryi. The highest number of fish species was recorded in 2024, with 48 species, significantly higher than the 39 species recorded in 2023. One-way ANOVA results indicated significant interannual differences in fish community diversity. In 2024, the fish diversity, richness, evenness, and dominance indices were the highest. The diversity index in 2024 (3.04) was significantly higher (P < 0.05) than in the previous three years. The richness index (6.86) was significantly higher (P < 0.05) than in 2023, and the evenness index (0.79) was significantly higher (P < 0.05) than in 2022. The abundance/biomass curve results showed that after the implementation of the fishing ban, the fish community structure in the Zhenjiang section was generally less disturbed. However, in 2022, the fish community was moderately disturbed due to abnormally low water levels, leading to decreased stability. By 2024, the fish community had preliminarily reached a stable state. Cluster and NMDS analyses indicated that the fish community in the Zhenjiang section was grouped into two clusters: 2021 and 2022–2024. Compared with 2021, the relative abundances of small fish such as Pelteobagrus nitidus, Hemiculter bleekeri, and Xenocypris argentea decreased from 2022 to 2024, while the relative abundance of Coilia nasus increased, reflecting certain successional characteristics in the community structure. After the ten-year fishing ban in the Yangtze River, fish resources in the Zhenjiang section showed a gradual recovery trend, and the community remained relatively stable. However, the recovery of the fish community was not a simple linear progression but was simultaneously influenced by both the “fishing ban (positive)” and “extremely low water levels (negative)” factors. This study clarifies the basic characteristics and trends of the fish community in the Zhenjiang section since the implementation of the ten-year fishing ban, providing support for evaluating the effectiveness of the fishing ban and assessing the aquatic biological integrity index. It also contributes to the steady and long-term implementation of the ten-year fishing ban policy in the Yangtze River.
To understand the changes in fish community structure and diversity in the Zhenjiang section of the Yangtze River since the implementation of the ten-year fishing ban, this study conducted surveys once during the fish breeding period (April–July) and once during the fattening period (September–November) each year from 2021 to 2024. Over the four-year period, a total of 792 net hauls were conducted in the Zhenjiang section, collecting 3,908 fish weighing 575.62?kg. A total of 66 fish species were identified, belonging to 9 orders, 16 families, and 47 genera. During the study period, the fish assemblage in the Zhenjiang reach of the Yangtze River was dominated by omnivorous (carnivorous) species, freshwater resident species, and benthic fish, accounting for 40.91% (40.91%), 69.70%, and 43.94% of the total species, respectively. The dominant species were Parabramis pekinensis, Hemiculter bleekeri, and Saurogobio dabryi. The highest number of fish species was recorded in 2024, with 48 species, significantly higher than the 39 species recorded in 2023. One-way ANOVA results indicated significant interannual differences in fish community diversity. In 2024, the fish diversity, richness, evenness, and dominance indices were the highest. The diversity index in 2024 (3.04) was significantly higher (P < 0.05) than in the previous three years. The richness index (6.86) was significantly higher (P < 0.05) than in 2023, and the evenness index (0.79) was significantly higher (P < 0.05) than in 2022. The abundance/biomass curve results showed that after the implementation of the fishing ban, the fish community structure in the Zhenjiang section was generally less disturbed. However, in 2022, the fish community was moderately disturbed due to abnormally low water levels, leading to decreased stability. By 2024, the fish community had preliminarily reached a stable state. Cluster and NMDS analyses indicated that the fish community in the Zhenjiang section was grouped into two clusters: 2021 and 2022–2024. Compared with 2021, the relative abundances of small fish such as Pelteobagrus nitidus, Hemiculter bleekeri, and Xenocypris argentea decreased from 2022 to 2024, while the relative abundance of Coilia nasus increased, reflecting certain successional characteristics in the community structure. After the ten-year fishing ban in the Yangtze River, fish resources in the Zhenjiang section showed a gradual recovery trend, and the community remained relatively stable. However, the recovery of the fish community was not a simple linear progression but was simultaneously influenced by both the “fishing ban (positive)” and “extremely low water levels (negative)” factors. This study clarifies the basic characteristics and trends of the fish community in the Zhenjiang section since the implementation of the ten-year fishing ban, providing support for evaluating the effectiveness of the fishing ban and assessing the aquatic biological integrity index. It also contributes to the steady and long-term implementation of the ten-year fishing ban policy in the Yangtze River.
Available online: May 07, 2026
Abstract:
The full open discharge scouring during flood season is important for the scouring of Sanmenxia reservoir, and often presents a scouring-equilibrium process. But the current related research is still insufficient. Using the combination methods of field data analysis, theory research, experiment study and model simulation, the sediment transport law and scouring-equilibrium process of full open discharge are studied. Data analysis show that the sediment transport rate of full open discharge during flood season can be calculated by the power law relationship model by addition of the upstream sediment supply function, in which the sediment transport coefficient decrease with the increase of accumulated scouring time and volume. The decrease of sediment transport coefficient is a fundamental reason for the formation of the scouring-equilibrium process, and is an important reason for the unreasonable phenomenon of the power law index of discharge being less than 1.0 in previous calibrations. Furthermore, considering the difference of incipient motion condition for upper layer new deposited sediment and lower layer consolidated sediment, the power law relationship model is improved and the sediment transport coefficient is revised. It shows that the variation of revised sediment transport coefficient becomes more smooth and reasonable. Scouring experiment for the consolidated sediment proves that if the dry density of consolidated sediment increases slightly, the incipient motion condition (velocity, shear stress and discharge) will increase significantly. Finally, according to the principle of self-adjustment of alluvial river and using the delayed response model theory, the delayed response model for sediment transport coefficient and accumulated scouring volume are established and applied to simulate the scouring-equilibrium process of full open discharge for Sanmenxia reservoir. The simulation results show that the calculated curve of sediment transport coefficient varied with the accumulated scouring time are in agreement with the measured values, the calculated curve of accumulated scouring volume varied with the accumulated incoming water are in good agreement with the measured values. The values of determination coefficient and Nash-Sutcliffe efficiency are 0.98 and 0.98, which preliminarily illustrate the rationality of the proposed model.
The full open discharge scouring during flood season is important for the scouring of Sanmenxia reservoir, and often presents a scouring-equilibrium process. But the current related research is still insufficient. Using the combination methods of field data analysis, theory research, experiment study and model simulation, the sediment transport law and scouring-equilibrium process of full open discharge are studied. Data analysis show that the sediment transport rate of full open discharge during flood season can be calculated by the power law relationship model by addition of the upstream sediment supply function, in which the sediment transport coefficient decrease with the increase of accumulated scouring time and volume. The decrease of sediment transport coefficient is a fundamental reason for the formation of the scouring-equilibrium process, and is an important reason for the unreasonable phenomenon of the power law index of discharge being less than 1.0 in previous calibrations. Furthermore, considering the difference of incipient motion condition for upper layer new deposited sediment and lower layer consolidated sediment, the power law relationship model is improved and the sediment transport coefficient is revised. It shows that the variation of revised sediment transport coefficient becomes more smooth and reasonable. Scouring experiment for the consolidated sediment proves that if the dry density of consolidated sediment increases slightly, the incipient motion condition (velocity, shear stress and discharge) will increase significantly. Finally, according to the principle of self-adjustment of alluvial river and using the delayed response model theory, the delayed response model for sediment transport coefficient and accumulated scouring volume are established and applied to simulate the scouring-equilibrium process of full open discharge for Sanmenxia reservoir. The simulation results show that the calculated curve of sediment transport coefficient varied with the accumulated scouring time are in agreement with the measured values, the calculated curve of accumulated scouring volume varied with the accumulated incoming water are in good agreement with the measured values. The values of determination coefficient and Nash-Sutcliffe efficiency are 0.98 and 0.98, which preliminarily illustrate the rationality of the proposed model.
Available online: May 07, 2026
Abstract:
Abstract: To investigate the spatiotemporal dynamics of fish resources downstream of the Wudongde Hydropower Station, hydroacoustic surveys were conducted using a Simrad EK80 echosounder (200 kHz) from May 2024 to April 2025. These surveys were integrated with fish catch sampling conducted in May and November and monthly monitoring data from a fixed fish aggregation station located on the right bank downstream of the dam. The fish catch surveys collected 250 individuals representing 31 species across 24 genera and 6 families, with Carassius auratus dominating the assemblage (44.4%), followed by Coreius guichenoti (5.6%) and Hemiculter leucisculus (5.2%). Both species richness and abundance were higher in May than in November. The fixed aggregation station recorded a total of 35,026 individuals representing 55 species from 40 genera and 11 families. The assemblage was numerically dominated by Hemiculter leucisculus (54.90%), Culter alburnus (32.98%), and Lepturichthys fimbriata (5.11%), with daily catches exhibiting pronounced seasonal peaks between June and September. Hydroacoustic target strength corresponded to fish body lengths ranging from 10.1 to 117.4 cm, and monthly fish densities varied between 3.07 and 53.43 individuals per 1000 m3. Temporal trends in fish length and density derived from hydroacoustic data were consistent with those from catch surveys and showed significant monthly correlations with aggregation station data (density: R = 0.73, p < 0.01; body length during May–October: R = 0.82, p = 0.047), demonstrating strong complementarity between the two monitoring approaches in terms of spatial coverage (hydroacoustics) and temporal continuity (aggregation station). Hydroacoustic observations further revealed distinct seasonal spatial patterns of fish distribution downstream of the dam. During spring and early summer (March–June), spawning-driven aggregations dominated, with spawning grounds of different species shifting longitudinally within 1.8–12.0 km downstream of the dam across months. In contrast, during autumn and winter (September–March), fish distributions became increasingly dispersed, characterized by downstream diffusion, low-density conditions, and intermittent return movements. Overall, fish distribution dynamics downstream of the dam can be summarized as a seasonal cycle of reproduction-driven aggregation, dispersal, low-density persistence, and return migration. These findings provide a scientific basis for optimizing the operation of fish aggregation systems and ecological regulation downstream of large dams and highlight the value of integrating hydroacoustic monitoring with fish tracking, hydrological observations, and environmental data to further elucidate underlying driving mechanisms.
Abstract: To investigate the spatiotemporal dynamics of fish resources downstream of the Wudongde Hydropower Station, hydroacoustic surveys were conducted using a Simrad EK80 echosounder (200 kHz) from May 2024 to April 2025. These surveys were integrated with fish catch sampling conducted in May and November and monthly monitoring data from a fixed fish aggregation station located on the right bank downstream of the dam. The fish catch surveys collected 250 individuals representing 31 species across 24 genera and 6 families, with Carassius auratus dominating the assemblage (44.4%), followed by Coreius guichenoti (5.6%) and Hemiculter leucisculus (5.2%). Both species richness and abundance were higher in May than in November. The fixed aggregation station recorded a total of 35,026 individuals representing 55 species from 40 genera and 11 families. The assemblage was numerically dominated by Hemiculter leucisculus (54.90%), Culter alburnus (32.98%), and Lepturichthys fimbriata (5.11%), with daily catches exhibiting pronounced seasonal peaks between June and September. Hydroacoustic target strength corresponded to fish body lengths ranging from 10.1 to 117.4 cm, and monthly fish densities varied between 3.07 and 53.43 individuals per 1000 m3. Temporal trends in fish length and density derived from hydroacoustic data were consistent with those from catch surveys and showed significant monthly correlations with aggregation station data (density: R = 0.73, p < 0.01; body length during May–October: R = 0.82, p = 0.047), demonstrating strong complementarity between the two monitoring approaches in terms of spatial coverage (hydroacoustics) and temporal continuity (aggregation station). Hydroacoustic observations further revealed distinct seasonal spatial patterns of fish distribution downstream of the dam. During spring and early summer (March–June), spawning-driven aggregations dominated, with spawning grounds of different species shifting longitudinally within 1.8–12.0 km downstream of the dam across months. In contrast, during autumn and winter (September–March), fish distributions became increasingly dispersed, characterized by downstream diffusion, low-density conditions, and intermittent return movements. Overall, fish distribution dynamics downstream of the dam can be summarized as a seasonal cycle of reproduction-driven aggregation, dispersal, low-density persistence, and return migration. These findings provide a scientific basis for optimizing the operation of fish aggregation systems and ecological regulation downstream of large dams and highlight the value of integrating hydroacoustic monitoring with fish tracking, hydrological observations, and environmental data to further elucidate underlying driving mechanisms.
Available online: May 06, 2026
Abstract:
Poyang Lake is a key habitat for waterbirds along the East Asian–Australasian Flyway. Understanding the spatiotemporal dynamics of wintering waterbird diversity is critical for optimizing regional wetland conservation. Using waterbird survey data from 44 sites during 2013–2023, we quantified species richness, abundance, Shannon diversity and Pielou evenness to assess interannual trends, feeding-guild responses, contrasts inside versus outside protected areas, and spatial patterns of diversity. We recorded 109 wintering waterbird species from 7 orders and 16 families. Total abundance showed no significant long-term change, but community structure shifted markedly. Feeding guilds responded differently: diversity increased in guilds feeding on sedges and grasses, whereas the abundance of invertebrate-feeding guilds declined and tuber-feeding guilds showed a weak declining trend that was not statistically significant. Diversity was generally higher inside protected areas, yet abundance decreased inside reserves and increased outside, suggesting a redistribution of birds towards surrounding habitats. Based on mean Shannon diversity and its temporal change, sites were classified into diversity core, degradation-warning, recovery-potential and vulnerable areas, revealing strong spatial differentiation in wintering waterbird diversity across the lake. Against a backdrop of overall numerical stability, our results indicate substantial structural and functional reorganization of wintering waterbird communities and support tiered, spatially differentiated management that integrates feeding-guild responses and protected-area versus non-protected patterns to enhance population and habitat resilience in Poyang Lake.
Poyang Lake is a key habitat for waterbirds along the East Asian–Australasian Flyway. Understanding the spatiotemporal dynamics of wintering waterbird diversity is critical for optimizing regional wetland conservation. Using waterbird survey data from 44 sites during 2013–2023, we quantified species richness, abundance, Shannon diversity and Pielou evenness to assess interannual trends, feeding-guild responses, contrasts inside versus outside protected areas, and spatial patterns of diversity. We recorded 109 wintering waterbird species from 7 orders and 16 families. Total abundance showed no significant long-term change, but community structure shifted markedly. Feeding guilds responded differently: diversity increased in guilds feeding on sedges and grasses, whereas the abundance of invertebrate-feeding guilds declined and tuber-feeding guilds showed a weak declining trend that was not statistically significant. Diversity was generally higher inside protected areas, yet abundance decreased inside reserves and increased outside, suggesting a redistribution of birds towards surrounding habitats. Based on mean Shannon diversity and its temporal change, sites were classified into diversity core, degradation-warning, recovery-potential and vulnerable areas, revealing strong spatial differentiation in wintering waterbird diversity across the lake. Against a backdrop of overall numerical stability, our results indicate substantial structural and functional reorganization of wintering waterbird communities and support tiered, spatially differentiated management that integrates feeding-guild responses and protected-area versus non-protected patterns to enhance population and habitat resilience in Poyang Lake.
Available online: May 06, 2026
Abstract:
Freshwater lakes are hotspots in the global carbon cycle and significant sources of surface carbon emissions. This study focuses on the satellite lakes within the Poyang Lake Basin, the largest throughflow freshwater lake in China. By integrating cavity ring-down spectroscopy, stable isotope analysis, and organic matter spectroscopic analysis, we systematically investigate the spatiotemporal characteristics, methane (CH4) prduction pathways, and key driving factors of carbon dioxide (CO2) and CH4 emissions under different hydrological conditions. The results reveal that carbon emission fluxes from the satellite lakes in the Poyang Lake Basin exhibit significant spatiotemporal heterogeneity driven primarily by hydrological conditions. The seasonal patterns of CO2 emission fluxes varied across lakes of different scales. Large and medium-sized lakes exhibited higher emissions during the wet season due to enhanced terrestrial inputs and heterotrophic respiration, with a mean of 13.68 ± 26.77 mmol m-2 d-1.Conversely, small lakes (<10 km2) displayed higher emissions during the dry season, with an average flux of 18.23 ± 28.72 mmol m-2 d-1. Hotspots of CO2 emission remained concentrated in river inlets and shallow zones, which are strongly influenced by terrestrial inputs, with peak fluxes reaching up to 127.80 mmol m-2 d-1 during the wet season. Concurrently, CH4 emissions were consistently higher during the wet season than the dry season across all lakes. This seasonal difference was particularly pronounced in medium-sized lakes, where the average flux increased from 0.07 ± 0.12 mmol m-2 d-1 in the dry season to 0.27 ± 0.23 mmol m-2 d-1 in the wet season; however, localized peak emissions in the dry season could reach as high as 2.6 mmol m-2d-1. Stable isotope analysis revealed a shift in methanogenic pathways from the wet to the dry season. The overall range of αC narrowed, with the maximum value decreasing from 1.07 to 1.05, indicating a transition from coexisting hydrogenotrophic and acetoclastic methanogenesis during the wet season to a predominance of acetoclastic methanogenesis during the dry season. Further analysis indicated that the primary drivers of CO2 emissions shifted from allochthonous inputs and respiration in the wet season to autochthonous photochemical and biological degradation in the dry season. Similarly, CH4 production transitioned from benthic methanogenesis fueled by allochthonous substrates to the decomposition of autochthonous matter in local microenvironments. These findings demonstrate that catchment processes significantly affect throughflow lakes carbon emissions, contributing to a deeper understanding of the dynamics of lake carbon cycling.
Freshwater lakes are hotspots in the global carbon cycle and significant sources of surface carbon emissions. This study focuses on the satellite lakes within the Poyang Lake Basin, the largest throughflow freshwater lake in China. By integrating cavity ring-down spectroscopy, stable isotope analysis, and organic matter spectroscopic analysis, we systematically investigate the spatiotemporal characteristics, methane (CH4) prduction pathways, and key driving factors of carbon dioxide (CO2) and CH4 emissions under different hydrological conditions. The results reveal that carbon emission fluxes from the satellite lakes in the Poyang Lake Basin exhibit significant spatiotemporal heterogeneity driven primarily by hydrological conditions. The seasonal patterns of CO2 emission fluxes varied across lakes of different scales. Large and medium-sized lakes exhibited higher emissions during the wet season due to enhanced terrestrial inputs and heterotrophic respiration, with a mean of 13.68 ± 26.77 mmol m-2 d-1.Conversely, small lakes (<10 km2) displayed higher emissions during the dry season, with an average flux of 18.23 ± 28.72 mmol m-2 d-1. Hotspots of CO2 emission remained concentrated in river inlets and shallow zones, which are strongly influenced by terrestrial inputs, with peak fluxes reaching up to 127.80 mmol m-2 d-1 during the wet season. Concurrently, CH4 emissions were consistently higher during the wet season than the dry season across all lakes. This seasonal difference was particularly pronounced in medium-sized lakes, where the average flux increased from 0.07 ± 0.12 mmol m-2 d-1 in the dry season to 0.27 ± 0.23 mmol m-2 d-1 in the wet season; however, localized peak emissions in the dry season could reach as high as 2.6 mmol m-2d-1. Stable isotope analysis revealed a shift in methanogenic pathways from the wet to the dry season. The overall range of αC narrowed, with the maximum value decreasing from 1.07 to 1.05, indicating a transition from coexisting hydrogenotrophic and acetoclastic methanogenesis during the wet season to a predominance of acetoclastic methanogenesis during the dry season. Further analysis indicated that the primary drivers of CO2 emissions shifted from allochthonous inputs and respiration in the wet season to autochthonous photochemical and biological degradation in the dry season. Similarly, CH4 production transitioned from benthic methanogenesis fueled by allochthonous substrates to the decomposition of autochthonous matter in local microenvironments. These findings demonstrate that catchment processes significantly affect throughflow lakes carbon emissions, contributing to a deeper understanding of the dynamics of lake carbon cycling.
Available online: May 06, 2026
Abstract:
Fuxian Lake, China"s largest deep freshwater lake in terms of water storage capacity, has seen its water level decline since 2010 due to reduced inflow and other reasons, affecting the natural reproduction of its indigenous fish species. To protect the rare fish resources and biodiversity of Fuxian Lake, and to ensure the healthy and sustainable development of its ecosystem, it is imperative to determine a suitable ecological water level that promotes the habitat protection and restoration of its endemic fish species. This study focused on the endemic fish, Anabarilius grahami, of Fuxian Lake, taking it as the target species for analysis. Based on the habitat requirements of Anabarilius grahami during its growth period, three crucial habitat factors were identified: water temperature, flow velocity, and dissolved oxygen (DO). Given Fuxian Lake’s characteristic as a deep lake, a three-dimensional hydrodynamic and water quality model was constructed using the Environmental Fluid Dynamics Code (EFDC). The Vertical Cumulative Weighted Usable Area (VCWUA) tailored for deep lakes was proposed, leveraging the habitat simulation method to calculate the suitable ecological water level for Fuxian Lake and assess its feasibility. The study yielded several key findings: ①The spatial distribution characteristics of the Suitability Index(SI) for the three key habitat factors — water temperature, flow velocity, and DO — exhibit differences. The SI for water temperature and flow velocity show minimal variation at different depths and have little impact on the comprehensive HSI. However, the SI for DO decreases significantly when the water depth exceeds 15 meters, which is the main factor affecting the vertical distribution of suitable habitat space. ②The variation of the Weighted Usable Area (WUA) in the living space (0-20m underwater range) of Anabarilius grahami is the same under different water level schemes. As the water depth increases, the WUA first increases and then decreases, peaking at a depth of 15 meters underwater. ③By analyzing the relationship between the water level of Fuxian Lake and the VCWUA of Anabarilius grahami, it is observed that the VCWUA increases initially and then decreases as the water level rises. The target value of the suitable ecological water level corresponding to the maximum value of the curve is 1722.29 m. Considering predictions of water level changes driven by climate change and human activities, as well as the scale of water diversion projects implemented in the Fuxian Lake basin, it is deemed achievable to attain this target water level.
Fuxian Lake, China"s largest deep freshwater lake in terms of water storage capacity, has seen its water level decline since 2010 due to reduced inflow and other reasons, affecting the natural reproduction of its indigenous fish species. To protect the rare fish resources and biodiversity of Fuxian Lake, and to ensure the healthy and sustainable development of its ecosystem, it is imperative to determine a suitable ecological water level that promotes the habitat protection and restoration of its endemic fish species. This study focused on the endemic fish, Anabarilius grahami, of Fuxian Lake, taking it as the target species for analysis. Based on the habitat requirements of Anabarilius grahami during its growth period, three crucial habitat factors were identified: water temperature, flow velocity, and dissolved oxygen (DO). Given Fuxian Lake’s characteristic as a deep lake, a three-dimensional hydrodynamic and water quality model was constructed using the Environmental Fluid Dynamics Code (EFDC). The Vertical Cumulative Weighted Usable Area (VCWUA) tailored for deep lakes was proposed, leveraging the habitat simulation method to calculate the suitable ecological water level for Fuxian Lake and assess its feasibility. The study yielded several key findings: ①The spatial distribution characteristics of the Suitability Index(SI) for the three key habitat factors — water temperature, flow velocity, and DO — exhibit differences. The SI for water temperature and flow velocity show minimal variation at different depths and have little impact on the comprehensive HSI. However, the SI for DO decreases significantly when the water depth exceeds 15 meters, which is the main factor affecting the vertical distribution of suitable habitat space. ②The variation of the Weighted Usable Area (WUA) in the living space (0-20m underwater range) of Anabarilius grahami is the same under different water level schemes. As the water depth increases, the WUA first increases and then decreases, peaking at a depth of 15 meters underwater. ③By analyzing the relationship between the water level of Fuxian Lake and the VCWUA of Anabarilius grahami, it is observed that the VCWUA increases initially and then decreases as the water level rises. The target value of the suitable ecological water level corresponding to the maximum value of the curve is 1722.29 m. Considering predictions of water level changes driven by climate change and human activities, as well as the scale of water diversion projects implemented in the Fuxian Lake basin, it is deemed achievable to attain this target water level.
Available online: April 29, 2026
Abstract:
To elucidate the hydrological evolution patterns of Lake Taihu, this study utilized compiled hydrological data from 1986–2024, employing inflow/outflow volumes and water retention time as key indicators. Mann-Kendall trend tests and other statistical methods were applied to analyze trend and periodic characteristics, identify abrupt change points, and investigate driving factors. The results shows that: (1) Both the inflow and outflow of water have shown a significant upward trend and experienced a sudden change in 2007, with main cycles at 23-25 years, 14 years, and 9 years. (2) Spatially, the spatial structure of the inflow of water has been reconstructed. The inflow and proportion in Huxi area of the lake have shown a significant upward trend, while the inflow in Zhexi area has slightly increased. The inflow from the Yangtze River to Taihu Lake has risen to the third place. The inflow in the Wuchengxiyu area and the Hangjiahu area has sharply decreased in 2009 and 2004, respectively. In terms of outflow, the WanYu River, Zhexi area, and the Hangjiahu area have shown a significant upward trend. (3) showed a significant decreasing trend with a synchronous abrupt change in 2007, dropping from 227 days annually before the change to 195 days; when accounting for peripheral water withdrawal, it decreased more sharply from 226 days to 172 days. After the 2007 change, water withdrawal caused an average reduction of 23 days in the retention time. Further analysis revealed that watershed precipitation was the primary driver in the early period (1986–2006), but after the 2007 change, engineering regulation significantly altered the inflow mechanisms in Huxi, Zhexi, and Wucheng-Xiyu areas. Consequently, total inflow around the lake (a composite of rainfall-runoff and artificial regulation) replaced precipitation as the dominant driving factor of the retention time.
To elucidate the hydrological evolution patterns of Lake Taihu, this study utilized compiled hydrological data from 1986–2024, employing inflow/outflow volumes and water retention time as key indicators. Mann-Kendall trend tests and other statistical methods were applied to analyze trend and periodic characteristics, identify abrupt change points, and investigate driving factors. The results shows that: (1) Both the inflow and outflow of water have shown a significant upward trend and experienced a sudden change in 2007, with main cycles at 23-25 years, 14 years, and 9 years. (2) Spatially, the spatial structure of the inflow of water has been reconstructed. The inflow and proportion in Huxi area of the lake have shown a significant upward trend, while the inflow in Zhexi area has slightly increased. The inflow from the Yangtze River to Taihu Lake has risen to the third place. The inflow in the Wuchengxiyu area and the Hangjiahu area has sharply decreased in 2009 and 2004, respectively. In terms of outflow, the WanYu River, Zhexi area, and the Hangjiahu area have shown a significant upward trend. (3) showed a significant decreasing trend with a synchronous abrupt change in 2007, dropping from 227 days annually before the change to 195 days; when accounting for peripheral water withdrawal, it decreased more sharply from 226 days to 172 days. After the 2007 change, water withdrawal caused an average reduction of 23 days in the retention time. Further analysis revealed that watershed precipitation was the primary driver in the early period (1986–2006), but after the 2007 change, engineering regulation significantly altered the inflow mechanisms in Huxi, Zhexi, and Wucheng-Xiyu areas. Consequently, total inflow around the lake (a composite of rainfall-runoff and artificial regulation) replaced precipitation as the dominant driving factor of the retention time.
Available online: April 29, 2026
Abstract:
To clarify the current situation of water resources reserved for exceptional drought in the water network area is the premise of improving the regional water network pattern and enhancing regional drought resistance. Aiming at the problems of unclear concept of water source reserve and lack of calculation method of reserve scale, this paper puts forward the definition of water source reserved for exceptional drought on the basis of analyzing existing concepts of water source reserve, and gives the calculation method of water source reserve scale for four types of water sources: lake and reservoir water, river water, groundwater and external water. The method was applied to the intake area of the middle route of the South-to-North Water Transfer project. The results showed that the total water reserved for exceptional drought of the intake area reached 12.252 billion m3, among which the water reserved by lake and reservoir, river, groundwater and transferred water accounted for 10.86%, 15.7%, 56.31% and 17.12% respectively. Among the 20 cities in the water receiving area, only 7 cities have the above 4 types of water sources in their water reserves to cope with severe drought, and 13 cities have groundwater reserves that account for more than 50%, and the type of water reserves is single. There are four cities with small reserve amount and single reserve type, so it is urgent to further improve the water resources reserve system for exceptional drought in the intake area of the middle route of the South-to-North Water Transfer project.
To clarify the current situation of water resources reserved for exceptional drought in the water network area is the premise of improving the regional water network pattern and enhancing regional drought resistance. Aiming at the problems of unclear concept of water source reserve and lack of calculation method of reserve scale, this paper puts forward the definition of water source reserved for exceptional drought on the basis of analyzing existing concepts of water source reserve, and gives the calculation method of water source reserve scale for four types of water sources: lake and reservoir water, river water, groundwater and external water. The method was applied to the intake area of the middle route of the South-to-North Water Transfer project. The results showed that the total water reserved for exceptional drought of the intake area reached 12.252 billion m3, among which the water reserved by lake and reservoir, river, groundwater and transferred water accounted for 10.86%, 15.7%, 56.31% and 17.12% respectively. Among the 20 cities in the water receiving area, only 7 cities have the above 4 types of water sources in their water reserves to cope with severe drought, and 13 cities have groundwater reserves that account for more than 50%, and the type of water reserves is single. There are four cities with small reserve amount and single reserve type, so it is urgent to further improve the water resources reserve system for exceptional drought in the intake area of the middle route of the South-to-North Water Transfer project.
Available online: April 29, 2026
Abstract:
The Qaidam Basin, located on the northeastern margin of the Tibetan Plateau, is characterized by a “mountain–deep basin” structural framework and Cenozoic sedimentary fill exceeding 10 km, which has given rise to China’s largest continental saline-lake potash metallogenic belt, containing over 80% of the nation’s proven reserves. Since the Neogene, the basin has undergone multiple phases of tectonic deformation. Under the combined influence of plateau uplift and extreme regional aridification, secondary depressions such as Qarhan, Dalangtan–Heibei, Kunteyi, and Mahai developed, forming a composite mineralization system dominated by brine-type deposits with coexisting solid–liquid mineralization. The potash-forming process is jointly controlled by four-dimensional factors: tectonics, climate, provenance, and sedimentation. Based on a systematic review of tectono-sedimentary evolution and paleoclimate changes, this study reconstructs the spatiotemporal distribution and controlling mechanisms of potash mineralization. The results indicate that tectonic differentiation determined the framework of brine accumulation and storage, climatic aridification drove evaporation concentration and mineralization rhythms, while sustained provenance supply provided sufficient material input. Combined with lithofacies–paleogeographic differentiation, the sedimentary center of the basin migrated repeatedly from the Early Pleistocene to the Holocene. On the basis of integrated analysis of metallogenic factors, the evolution of potash mineralization in the Qaidam Basin can be divided into five stages: unified paleolake subsidence, multi-depression differentiation, extreme aridification and concentration, fault-controlled inheritance and metallogenic climax, and the modern saline-lake cluster. Furthermore, three metallogenic models are identified: central sedimentary-center type, foreland thrust-belt-controlled type, and northwestern tectonically controlled type. This evolutionary sequence and model framework not only reveal the dynamic essence of saline-lake potash mineralization under the uplift of the Tibetan Plateau, but also provide a theoretical basis and practical guidance for deep brine exploration and the refinement of metallogenic models in China.
The Qaidam Basin, located on the northeastern margin of the Tibetan Plateau, is characterized by a “mountain–deep basin” structural framework and Cenozoic sedimentary fill exceeding 10 km, which has given rise to China’s largest continental saline-lake potash metallogenic belt, containing over 80% of the nation’s proven reserves. Since the Neogene, the basin has undergone multiple phases of tectonic deformation. Under the combined influence of plateau uplift and extreme regional aridification, secondary depressions such as Qarhan, Dalangtan–Heibei, Kunteyi, and Mahai developed, forming a composite mineralization system dominated by brine-type deposits with coexisting solid–liquid mineralization. The potash-forming process is jointly controlled by four-dimensional factors: tectonics, climate, provenance, and sedimentation. Based on a systematic review of tectono-sedimentary evolution and paleoclimate changes, this study reconstructs the spatiotemporal distribution and controlling mechanisms of potash mineralization. The results indicate that tectonic differentiation determined the framework of brine accumulation and storage, climatic aridification drove evaporation concentration and mineralization rhythms, while sustained provenance supply provided sufficient material input. Combined with lithofacies–paleogeographic differentiation, the sedimentary center of the basin migrated repeatedly from the Early Pleistocene to the Holocene. On the basis of integrated analysis of metallogenic factors, the evolution of potash mineralization in the Qaidam Basin can be divided into five stages: unified paleolake subsidence, multi-depression differentiation, extreme aridification and concentration, fault-controlled inheritance and metallogenic climax, and the modern saline-lake cluster. Furthermore, three metallogenic models are identified: central sedimentary-center type, foreland thrust-belt-controlled type, and northwestern tectonically controlled type. This evolutionary sequence and model framework not only reveal the dynamic essence of saline-lake potash mineralization under the uplift of the Tibetan Plateau, but also provide a theoretical basis and practical guidance for deep brine exploration and the refinement of metallogenic models in China.
zhuoyu, lijunle, likemao, jianshenglong, suixiaoyun, zhoushijia, zhangwanjing, jiayintao, chenyifeng
Available online: April 29, 2026
Abstract:
The indicator species approach is an important tool for assessing aquatic ecosystem health. Its effectiveness lies on the selection of species that are both sensitive to environmental changes and representative of the local ecological community. This study aimed to establish a fish-based indicator species framework suited to the upper reaches of the Yellow River. Drawing on field survey data collected from 2022 to 2023, Drawing on field survey data collected from 2022 to 2023, we integrated fish community distribution patterns with species-environment relationships using a multi-faceted analytical approach and validated the results using the Indicator Value (IndVal) method. First, redundancy analysis (RDA) was employed to explore the associations between fish distributions and environmental variables, assessing species-specific responses to individual environmental gradients. Subsequently, RLQ and Fourth-corner analyses were used to quantify the coupling between fish functional traits and environmental gradients. Species that exhibited significant responses in both analyses were selected as candidate indicator species. Six key indicator species were ultimately identified for the upper reaches of the Yellow River: Schizopygopsis pylzovi, Chuanchia labiosa, Gymnocypris eckloni, Platypharodon extremus, Gymnodiptychus pachycheilus, and Triplophysa siluroides. The IndVal method was then used to evaluate the strength of these species as indicators of specific habitats. Among them, five species—S. pylzovi, C. labiosa, P. extremus, G. pachycheilus, and T. siluroides—demonstrated statistically significant indicator values. Furthermore, the Random Forest Model was applied to examine the relationships between indicator species occurrence and environmental factors. Results revealed that the age of reservoir, age of aquaculture, and the cumulative number of dams were the most important predictors of species presence or absence. As these variables increased, the occurrence frequency of indicator species declined significantly. This study provides a methodological reference for the selection of indicator fish species and offers a scientific basis for the ecological protection and management of river basins. These findings offer a methodological basis for the identification of indicator species and provide valuable insights to support ecological monitoring, conservation planning, and watershed management in the Yellow River Basin.
The indicator species approach is an important tool for assessing aquatic ecosystem health. Its effectiveness lies on the selection of species that are both sensitive to environmental changes and representative of the local ecological community. This study aimed to establish a fish-based indicator species framework suited to the upper reaches of the Yellow River. Drawing on field survey data collected from 2022 to 2023, Drawing on field survey data collected from 2022 to 2023, we integrated fish community distribution patterns with species-environment relationships using a multi-faceted analytical approach and validated the results using the Indicator Value (IndVal) method. First, redundancy analysis (RDA) was employed to explore the associations between fish distributions and environmental variables, assessing species-specific responses to individual environmental gradients. Subsequently, RLQ and Fourth-corner analyses were used to quantify the coupling between fish functional traits and environmental gradients. Species that exhibited significant responses in both analyses were selected as candidate indicator species. Six key indicator species were ultimately identified for the upper reaches of the Yellow River: Schizopygopsis pylzovi, Chuanchia labiosa, Gymnocypris eckloni, Platypharodon extremus, Gymnodiptychus pachycheilus, and Triplophysa siluroides. The IndVal method was then used to evaluate the strength of these species as indicators of specific habitats. Among them, five species—S. pylzovi, C. labiosa, P. extremus, G. pachycheilus, and T. siluroides—demonstrated statistically significant indicator values. Furthermore, the Random Forest Model was applied to examine the relationships between indicator species occurrence and environmental factors. Results revealed that the age of reservoir, age of aquaculture, and the cumulative number of dams were the most important predictors of species presence or absence. As these variables increased, the occurrence frequency of indicator species declined significantly. This study provides a methodological reference for the selection of indicator fish species and offers a scientific basis for the ecological protection and management of river basins. These findings offer a methodological basis for the identification of indicator species and provide valuable insights to support ecological monitoring, conservation planning, and watershed management in the Yellow River Basin.
Available online: April 29, 2026
Abstract:
The increasing global demand for biodiversity conservation has made the accurate acquisition of biodiversity data a pressing challenge worldwide. Essential Biodiversity Variables (EBVs), as core indicators for biodiversity monitoring, provide a scientific foundation for both global and regional conservation policies. While traditional monitoring methods have contributed valuable data, they remain limited by high costs, low efficiency, and sampling difficulties. Remote sensing technology offers an effective global solution for the derivation of EBVs, but its application to aquatic biodiversity monitoring remains constrained, particularly with respect to genetic diversity. Environmental DNA (eDNA), as an emerging tool, enables efficient and precise detection of diverse species within environmental samples, thereby supplying richer datasets for the development of EBVs. This paper highlights the potential of eDNA technology in advancing EBV construction and examines its prospects in biodiversity conservation in China, with the goal of fostering stronger integration between scientific research and policy-making. Using the six classes of EBVs as an analytical framework, this study reviewed 23 national and regional guidelines for aquatic biodiversity monitoring in China. The results revealed a strong dominance of community-level indicators, with approximately 95% of guidelines focusing on community composition, while genetic diversity, quantitative population dynamics, and ecosystem structure and function remain poorly represented. Considerable inconsistencies also existed among guidelines issued by different administrative sectors, limiting long-term comparability. Environmental DNA, with its high sensitivity, non-invasive sampling, and broad taxonomic coverage, offers a promising approach to address these structural gaps and support the development of EBV-aligned aquatic biodiversity monitoring systems.
The increasing global demand for biodiversity conservation has made the accurate acquisition of biodiversity data a pressing challenge worldwide. Essential Biodiversity Variables (EBVs), as core indicators for biodiversity monitoring, provide a scientific foundation for both global and regional conservation policies. While traditional monitoring methods have contributed valuable data, they remain limited by high costs, low efficiency, and sampling difficulties. Remote sensing technology offers an effective global solution for the derivation of EBVs, but its application to aquatic biodiversity monitoring remains constrained, particularly with respect to genetic diversity. Environmental DNA (eDNA), as an emerging tool, enables efficient and precise detection of diverse species within environmental samples, thereby supplying richer datasets for the development of EBVs. This paper highlights the potential of eDNA technology in advancing EBV construction and examines its prospects in biodiversity conservation in China, with the goal of fostering stronger integration between scientific research and policy-making. Using the six classes of EBVs as an analytical framework, this study reviewed 23 national and regional guidelines for aquatic biodiversity monitoring in China. The results revealed a strong dominance of community-level indicators, with approximately 95% of guidelines focusing on community composition, while genetic diversity, quantitative population dynamics, and ecosystem structure and function remain poorly represented. Considerable inconsistencies also existed among guidelines issued by different administrative sectors, limiting long-term comparability. Environmental DNA, with its high sensitivity, non-invasive sampling, and broad taxonomic coverage, offers a promising approach to address these structural gaps and support the development of EBV-aligned aquatic biodiversity monitoring systems.
Available online: April 29, 2026
Abstract:
Urban lakes serve multiple functions including flood storage, water supply, landscape tourism, and ecological maintenance, possessing significant ecological, environmental, and socio-economic value. Yangtze River Basin hosts approximately 355,000 urban lakes, accounting for over 65% of the nation"s total water area. These lakes exhibit strong ecological functions. Currently, urban lakes in the Yangtze River Basin face prominent challenges such as high non-point source pollution loads during flood seasons, pollution risks associated with ecological water supplementation safety, and weak resilience of aquatic ecosystems. Addressing these issues requires an integrated approach that considers the holistic nature of urban lake ecosystems and the systemic characteristics of the river basin. Advancing coordinated water environment and aquatic ecosystem management under a source–sewer–treatment plant–river–lake integrated framework. This study provides a systematic review of the research status and development needs related to the coordinated governance of water environment and aquatic ecosystems in urban lakes of the Yangtze River Basin. It synthesizes recent progress in domestic and international research as well as practical engineering applications, and offers an in-depth analysis of the major challenges currently constraining coordinated governance: (1) In certain urban areas, the issues of pollutant accumulation during dry seasons and the episodic release of contaminants during rainfall events remain prominent. Notably, storm-induced non-point source pollution has increasingly become a key constraint on the sustained improvement of urban water environments; (2) The critical challenge for using effluents from municipal wastewater treatment plants as ecological replenishment for urban lakes lies in achieving water quality and aquatic ecosystem compatibility between reclaimed water and receiving lake bodies; (3) The ecological resilience of lake ecosystems remains weak, and watershed-level systematic governance is still insufficient. Based on this analysis, we summarize targeted strategies and key tasks centered on "pollution source identification and perception - efficient external source control - water supplementation safety - habitat restoration and reconstruction - system optimization and configuration - integrated platform management," aiming to accelerate new achievements in the ecological environment governance of urban lakes in the Yangtze River Basin and provide scientific and technological support for national ecological civilization construction and green development strategy implementation.
Urban lakes serve multiple functions including flood storage, water supply, landscape tourism, and ecological maintenance, possessing significant ecological, environmental, and socio-economic value. Yangtze River Basin hosts approximately 355,000 urban lakes, accounting for over 65% of the nation"s total water area. These lakes exhibit strong ecological functions. Currently, urban lakes in the Yangtze River Basin face prominent challenges such as high non-point source pollution loads during flood seasons, pollution risks associated with ecological water supplementation safety, and weak resilience of aquatic ecosystems. Addressing these issues requires an integrated approach that considers the holistic nature of urban lake ecosystems and the systemic characteristics of the river basin. Advancing coordinated water environment and aquatic ecosystem management under a source–sewer–treatment plant–river–lake integrated framework. This study provides a systematic review of the research status and development needs related to the coordinated governance of water environment and aquatic ecosystems in urban lakes of the Yangtze River Basin. It synthesizes recent progress in domestic and international research as well as practical engineering applications, and offers an in-depth analysis of the major challenges currently constraining coordinated governance: (1) In certain urban areas, the issues of pollutant accumulation during dry seasons and the episodic release of contaminants during rainfall events remain prominent. Notably, storm-induced non-point source pollution has increasingly become a key constraint on the sustained improvement of urban water environments; (2) The critical challenge for using effluents from municipal wastewater treatment plants as ecological replenishment for urban lakes lies in achieving water quality and aquatic ecosystem compatibility between reclaimed water and receiving lake bodies; (3) The ecological resilience of lake ecosystems remains weak, and watershed-level systematic governance is still insufficient. Based on this analysis, we summarize targeted strategies and key tasks centered on "pollution source identification and perception - efficient external source control - water supplementation safety - habitat restoration and reconstruction - system optimization and configuration - integrated platform management," aiming to accelerate new achievements in the ecological environment governance of urban lakes in the Yangtze River Basin and provide scientific and technological support for national ecological civilization construction and green development strategy implementation.
Zhang Yaning, He Xinlin, Dong Ying, Wu Xijun, Liu Jing, Peng Yan, Zhang Fuchu, Song Weihao, Zhao Jian
Available online: April 28, 2026
Abstract:
To clarify the impact of different pollution sources on the ecological environment and human health risks, the typical river in the northern Shaanxi Energy and Chemical Industry Base was taken as the research object. The contents of heavy metals (Cu, Zn, Pb, Cd, Ni, Cr, Hg and As) in 59 sediment samples were collected and measured during the wet and dry seasons. The Geo-accumulation Index (Igeo) and Nemerow Index (P) were used to assess the heavy metal pollution level; the Positive Matrix Factorization model (PMF) was applied to quantitatively identify the sources of heavy metals. Furthermore, the contribution of each pollution sources to potential ecological risks and human health risks was quantitatively analyzed by combining PMF with the potential ecological risk model (RI) and the human health risk assessment model (HRA). The results showed that the average concentration of Hg in the sediment decreased from 0.10 mg·kg?1 in the wet season to 0.01 mg·kg?1 in the dry season, while the concentrations of the other seven heavy metals in the dry season were significantly higher than those in the wet season. The average content of eight heavy metals was at the non-pollution or low-pollution level, while the overall pollution level was relatively high. The PMF results based on receptor concentration indicated that heavy metal pollution during the wet season mainly came from industrial sources (48.23%), transportation sources (31.06%), agricultural sources (11.84%), and coal mining sources (8.87%); During the dry season, heavy metals are mainly affected by industrial sources (58.83%), coal mining sources (28.12%), and transportation sources (13.05%). Results from the PMF-RI/HRA coupling model based on pollution sources showed that the average comprehensive ecological risk indices (RI) in the wet season and dry season were 160.27 and 147.00, respectively, corresponding to "moderate risk" and "low risk" levels. The wet-season risk was mainly driven by Hg emissions (98.46%) from coal mining sources (48.27%), while the dry-season risk was mainly driven by Cd emissions (69.52%) from industrial sources (46.87%). Carcinogenic risks were evident in all populations, with boys facing the highest risk, which was mainly attributed to Ni exposure (≥80.13%) from industrial source pollution (≥51.47%). The results of the pollution source-oriented ecological and health risk assessment provide a scientific basis for pollution prevention and control in such areas.
To clarify the impact of different pollution sources on the ecological environment and human health risks, the typical river in the northern Shaanxi Energy and Chemical Industry Base was taken as the research object. The contents of heavy metals (Cu, Zn, Pb, Cd, Ni, Cr, Hg and As) in 59 sediment samples were collected and measured during the wet and dry seasons. The Geo-accumulation Index (Igeo) and Nemerow Index (P) were used to assess the heavy metal pollution level; the Positive Matrix Factorization model (PMF) was applied to quantitatively identify the sources of heavy metals. Furthermore, the contribution of each pollution sources to potential ecological risks and human health risks was quantitatively analyzed by combining PMF with the potential ecological risk model (RI) and the human health risk assessment model (HRA). The results showed that the average concentration of Hg in the sediment decreased from 0.10 mg·kg?1 in the wet season to 0.01 mg·kg?1 in the dry season, while the concentrations of the other seven heavy metals in the dry season were significantly higher than those in the wet season. The average content of eight heavy metals was at the non-pollution or low-pollution level, while the overall pollution level was relatively high. The PMF results based on receptor concentration indicated that heavy metal pollution during the wet season mainly came from industrial sources (48.23%), transportation sources (31.06%), agricultural sources (11.84%), and coal mining sources (8.87%); During the dry season, heavy metals are mainly affected by industrial sources (58.83%), coal mining sources (28.12%), and transportation sources (13.05%). Results from the PMF-RI/HRA coupling model based on pollution sources showed that the average comprehensive ecological risk indices (RI) in the wet season and dry season were 160.27 and 147.00, respectively, corresponding to "moderate risk" and "low risk" levels. The wet-season risk was mainly driven by Hg emissions (98.46%) from coal mining sources (48.27%), while the dry-season risk was mainly driven by Cd emissions (69.52%) from industrial sources (46.87%). Carcinogenic risks were evident in all populations, with boys facing the highest risk, which was mainly attributed to Ni exposure (≥80.13%) from industrial source pollution (≥51.47%). The results of the pollution source-oriented ecological and health risk assessment provide a scientific basis for pollution prevention and control in such areas.
Available online: April 28, 2026
Abstract:
Abstract:To systematically reveal the sediment pollution characteristics, endogenous release risks, and primary pollution sources in Qilu Lake, a heavily polluted plateau lake in Yunnan, and to provide a scientific basis for its precise and effective management, a comprehensive sediment investigation was conducted across the entire lake from 2024 to 2025. This study involved collecting samples from 20 sites to determine the concentrations of total nitrogen (TN), total phosphorus (TP), organic matter (OM), and various heavy metals, with their spatial distribution patterns analyzed using GIS. Concurrently, laboratory static incubation experiments were performed on sediments from three typical areas—the western estuary, the lake"s center, and the northeastern region—to quantify the release fluxes and transformation patterns of nitrogen and phosphorus. Finally, methods such as Nemerow"s comprehensive pollution index and Principal Component Analysis (PCA) were employed to assess the pollution degree and identify the main sources. The results indicated that the sediments of Qilu Lake act as a massive "pollution reservoir" and are extremely polluted, with surface sediment concentrations of TN, TP, and OM ranging from 2120–11300 mg/kg, 270–2280 mg/kg, and 41.4–260 g/kg, respectively. The Nemerow"s index assessment revealed that 70% of the sampling sites reached moderate to severe pollution levels (PN > 2.0), with TN being the primary determining factor for the pollution. The pollutant distribution exhibited significant spatial heterogeneity, forming "pollution hotspots" in the southwestern estuary area, which receives terrestrial inputs, and in the central lake area, which serves as a deposition center for endogenous biomass. PCA clearly distinguished two major categories of pollution sources: (1) a composite source of agricultural non-point and industrial pollution, characterized by TP and various heavy metals (especially Cd, Pb, Cu, Zn); and (2) an organic pollution source, characterized by TN and OM, originating from domestic sewage and endogenous biological contributions. The static release experiments confirmed that the sediment is a strong internal source of nitrogen and phosphorus. The central and northeastern parts of the lake were identified as the main "high-efficiency release zones," with a maximum TP release flux of up to 2.80 mg/(m2·d) and an ammonia nitrogen release flux as high as 146.1 mg/(m2·d). In contrast, the western estuary area exhibited a unique net absorption of total nitrogen, suggesting its potential as a "denitrification functional zone." The core innovation of this study lies in revealing, for the first time, the spatial heterogeneity and functional differentiation between the "stock" (pollutant storage) and "risk" (release potential) of internal pollution in Qilu Lake. The study found that the western estuary area, despite having the highest pollutant stock, exhibited unique net total nitrogen absorption in its release mechanisms, identifying it as a potential "denitrification functional zone." Conversely, the central and northeastern areas, although some parts do not have the highest pollutant stock, function as the "high-efficiency release zones" for nitrogen and phosphorus. This finding not only deepens the understanding of the complexity of biogeochemical processes in heavily polluted shallow lakes but, more importantly, This provides the critical scientific evidence for evolving endogenous pollution remediation in lakes, moving away from conventional, simplistic, holistic approaches to a precision, zone-based management and control strategy informed by "source-sink" patterns and functional differentiation.
Abstract:To systematically reveal the sediment pollution characteristics, endogenous release risks, and primary pollution sources in Qilu Lake, a heavily polluted plateau lake in Yunnan, and to provide a scientific basis for its precise and effective management, a comprehensive sediment investigation was conducted across the entire lake from 2024 to 2025. This study involved collecting samples from 20 sites to determine the concentrations of total nitrogen (TN), total phosphorus (TP), organic matter (OM), and various heavy metals, with their spatial distribution patterns analyzed using GIS. Concurrently, laboratory static incubation experiments were performed on sediments from three typical areas—the western estuary, the lake"s center, and the northeastern region—to quantify the release fluxes and transformation patterns of nitrogen and phosphorus. Finally, methods such as Nemerow"s comprehensive pollution index and Principal Component Analysis (PCA) were employed to assess the pollution degree and identify the main sources. The results indicated that the sediments of Qilu Lake act as a massive "pollution reservoir" and are extremely polluted, with surface sediment concentrations of TN, TP, and OM ranging from 2120–11300 mg/kg, 270–2280 mg/kg, and 41.4–260 g/kg, respectively. The Nemerow"s index assessment revealed that 70% of the sampling sites reached moderate to severe pollution levels (PN > 2.0), with TN being the primary determining factor for the pollution. The pollutant distribution exhibited significant spatial heterogeneity, forming "pollution hotspots" in the southwestern estuary area, which receives terrestrial inputs, and in the central lake area, which serves as a deposition center for endogenous biomass. PCA clearly distinguished two major categories of pollution sources: (1) a composite source of agricultural non-point and industrial pollution, characterized by TP and various heavy metals (especially Cd, Pb, Cu, Zn); and (2) an organic pollution source, characterized by TN and OM, originating from domestic sewage and endogenous biological contributions. The static release experiments confirmed that the sediment is a strong internal source of nitrogen and phosphorus. The central and northeastern parts of the lake were identified as the main "high-efficiency release zones," with a maximum TP release flux of up to 2.80 mg/(m2·d) and an ammonia nitrogen release flux as high as 146.1 mg/(m2·d). In contrast, the western estuary area exhibited a unique net absorption of total nitrogen, suggesting its potential as a "denitrification functional zone." The core innovation of this study lies in revealing, for the first time, the spatial heterogeneity and functional differentiation between the "stock" (pollutant storage) and "risk" (release potential) of internal pollution in Qilu Lake. The study found that the western estuary area, despite having the highest pollutant stock, exhibited unique net total nitrogen absorption in its release mechanisms, identifying it as a potential "denitrification functional zone." Conversely, the central and northeastern areas, although some parts do not have the highest pollutant stock, function as the "high-efficiency release zones" for nitrogen and phosphorus. This finding not only deepens the understanding of the complexity of biogeochemical processes in heavily polluted shallow lakes but, more importantly, This provides the critical scientific evidence for evolving endogenous pollution remediation in lakes, moving away from conventional, simplistic, holistic approaches to a precision, zone-based management and control strategy informed by "source-sink" patterns and functional differentiation.
Available online: April 28, 2026
Abstract:
Dissolved gases are key byproducts of biogeochemical reactions and serve as critical indicators for the evolution of aquatic ecosystems. However, traditional headspace equilibrium sampling methods are prone to air contamination, decompression-induced degassing, and limited measurement precision. To address these challenges, this study developed an in-situ system for the simultaneous determination of multiple dissolved gases in deep waters. The method was applied to characterize the distribution of dissolved gases in the Three Gorges Reservoir. Results demonstrated that the proposed method achieves high-precision, simultaneous in-situ measurements of five key gases—methane (CH4), nitrogen (N2), oxygen (O2), argon (Ar), and carbon dioxide (CO2)—at depths of up to 100 meters. High-precision calibration models were established for these five gases through systematic multi-temperature and multi-concentration calibration, achieving a measurement resolution of 1 ppm. Compared to traditional headspace sampling, this approach effectively eliminates air interference and decompression degassing, significantly enhancing data fidelity. Field validation against commercial high-precision instruments (Picarro greenhouse gas analyzer and multi-parameter water quality sondes) demonstrated exceptional consistency (R2 > 0.96; Concordance Correlation Coefficient [CCC] > 0.98), confirming the accuracy and reliability of the measurements. Furthermore, the proposed method surpasses traditional techniques in terms of real-time performance, spatial resolution, and monitoring efficiency. Field application in the Pengxi River Bay of the Three Gorges Reservoir successfully generated high-resolution two-dimensional distribution profiles along a 42-km longitudinal section. The results clearly revealed distinct vertical stratification, extensive bottom water hypoxia, and coupled accumulation of CO2 and CH4 during summer and autumn, effectively identifying hotspots of intense biogeochemical activity. This in-situ monitoring technology matches the accuracy of traditional laboratory methods while offering superior data fidelity, spatiotemporal resolution, and monitoring efficiency. It provides innovative technical support for greenhouse gas emission assessment, water quality management, aquatic nitrogen cycling, and the study of material cycling and ecological evolution in complex aquatic environments.
Dissolved gases are key byproducts of biogeochemical reactions and serve as critical indicators for the evolution of aquatic ecosystems. However, traditional headspace equilibrium sampling methods are prone to air contamination, decompression-induced degassing, and limited measurement precision. To address these challenges, this study developed an in-situ system for the simultaneous determination of multiple dissolved gases in deep waters. The method was applied to characterize the distribution of dissolved gases in the Three Gorges Reservoir. Results demonstrated that the proposed method achieves high-precision, simultaneous in-situ measurements of five key gases—methane (CH4), nitrogen (N2), oxygen (O2), argon (Ar), and carbon dioxide (CO2)—at depths of up to 100 meters. High-precision calibration models were established for these five gases through systematic multi-temperature and multi-concentration calibration, achieving a measurement resolution of 1 ppm. Compared to traditional headspace sampling, this approach effectively eliminates air interference and decompression degassing, significantly enhancing data fidelity. Field validation against commercial high-precision instruments (Picarro greenhouse gas analyzer and multi-parameter water quality sondes) demonstrated exceptional consistency (R2 > 0.96; Concordance Correlation Coefficient [CCC] > 0.98), confirming the accuracy and reliability of the measurements. Furthermore, the proposed method surpasses traditional techniques in terms of real-time performance, spatial resolution, and monitoring efficiency. Field application in the Pengxi River Bay of the Three Gorges Reservoir successfully generated high-resolution two-dimensional distribution profiles along a 42-km longitudinal section. The results clearly revealed distinct vertical stratification, extensive bottom water hypoxia, and coupled accumulation of CO2 and CH4 during summer and autumn, effectively identifying hotspots of intense biogeochemical activity. This in-situ monitoring technology matches the accuracy of traditional laboratory methods while offering superior data fidelity, spatiotemporal resolution, and monitoring efficiency. It provides innovative technical support for greenhouse gas emission assessment, water quality management, aquatic nitrogen cycling, and the study of material cycling and ecological evolution in complex aquatic environments.
zhao rui, Lu Mansheng, Huang Junteng, Li Shengping, Liu Wanxin, Zhang Shulin, Tang Jiaxin, Zheng Jiazhong, Yong Bin, Wang Weiguang
Available online: April 28, 2026
Abstract:
River discharge serves as a critical variable in basin hydrological processes, playing a vital role in flood control, water resource planning, and management. Due to harsh natural environments and climatic conditions, discharge observation stations are scarce in the Yangtze River source region located on the eastern edge of the Qinghai-Tibet Plateau, making it a typical data-deficient area. Therefore, conducting discharge estimation in this region is of significant importance for ensuring water security in the Yangtze River basin and protecting regional ecosystems. This study establishes virtual stations upstream and downstream of the Zhimenda hydrological station in the Yangtze headwaters (ZMD_1 and ZMD_2) as reference points. Utilizing Sentinel-2 and Jason-3, and Sentinel-3A satellite remote sensing data. A novel quantile matching approach was employed to fuse remotely sensed water level and river width data. The Manning"s equation was modified based on generalized cross-section profiles to conduct quantitative discharge estimation for the Yangtze headwaters. Results indicate that the new method achieves high esti-mation accuracy at both virtual stations, with Nash"s efficiency coefficients (NSE) exceeding 0.74. The root mean square error (RMSE) of estimated discharges was 302.13 m3/s and 316.46 m3/s, respectively, with relative root mean square errors (RRMSE) of 30.0% and 32.8%. Overall, discharge estimation accuracy at the ZMD_1 virtual station outperformed that at ZMD_2. The ZMD_2 virtual station results exhibited significant fluctuations, primarily due to the presence of mid-channel bars within the ZMD_2 buffer zone, which compromised the accuracy of flow inversion at the virtual station. This study, based on multi-source satellite remote sensing for estimating river flows in the Yangtze River source region, provides theoretical methods and technical references for flow estimation in data-scarce areas.
River discharge serves as a critical variable in basin hydrological processes, playing a vital role in flood control, water resource planning, and management. Due to harsh natural environments and climatic conditions, discharge observation stations are scarce in the Yangtze River source region located on the eastern edge of the Qinghai-Tibet Plateau, making it a typical data-deficient area. Therefore, conducting discharge estimation in this region is of significant importance for ensuring water security in the Yangtze River basin and protecting regional ecosystems. This study establishes virtual stations upstream and downstream of the Zhimenda hydrological station in the Yangtze headwaters (ZMD_1 and ZMD_2) as reference points. Utilizing Sentinel-2 and Jason-3, and Sentinel-3A satellite remote sensing data. A novel quantile matching approach was employed to fuse remotely sensed water level and river width data. The Manning"s equation was modified based on generalized cross-section profiles to conduct quantitative discharge estimation for the Yangtze headwaters. Results indicate that the new method achieves high esti-mation accuracy at both virtual stations, with Nash"s efficiency coefficients (NSE) exceeding 0.74. The root mean square error (RMSE) of estimated discharges was 302.13 m3/s and 316.46 m3/s, respectively, with relative root mean square errors (RRMSE) of 30.0% and 32.8%. Overall, discharge estimation accuracy at the ZMD_1 virtual station outperformed that at ZMD_2. The ZMD_2 virtual station results exhibited significant fluctuations, primarily due to the presence of mid-channel bars within the ZMD_2 buffer zone, which compromised the accuracy of flow inversion at the virtual station. This study, based on multi-source satellite remote sensing for estimating river flows in the Yangtze River source region, provides theoretical methods and technical references for flow estimation in data-scarce areas.
Available online: April 23, 2026
Abstract:
Phytoplankton, as the primary producers in lake ecosystems, influence material cycling and energy flow within water bodies. Their community structure and dynamic changes directly reflect the nutrient status and ecological health of the water body. To comprehensively understand phytoplankton variations and influencing factors in tailwater lakes of northern arid-cold regions, the representative Daihai Lake was selected as the study site. Water and sediment samples were collected across all four seasons in 2024 to systematically analyse phytoplankton community structure and its response to environmental factors. Results indicate that during the study period, water body total nitrogen (TN) and total phosphorus (TP) concentrations exceeded Class V and Class IV water standards, respectively, while sediment TN and TP contents surpassed the national sediment average. A total of 95 phytoplankton species belonging to 8 phyla were identified, dominated by Chlorophyta, Cyanobacteria, and Diatomeae. Phytoplankton cell density, biomass, and Chl.a concentration peaked in winter. Ten dominant species across 5 phyla were identified, primarily from Chlorophyta and Diatomeae, with Microcystis and Chromomonas serving as key dominant species throughout the year. Results from Shannon diversity index, Pielou evenness index, Margalef richness index, and Simpson dominance index indicated higher phytoplankton community diversity and greater ecosystem stability in spring and summer compared to autumn and winter. Phytoplankton communities in Daihai Lake exhibited low spatial heterogeneity, suggesting that diversity and richness are primarily influenced by seasonal variations. Statistical analysis indicates that water temperature (WT), pH, dissolved oxygen (DO), total nitrogen (TN), and dissolved inorganic phosphorus (DIP) are key factors influencing phytoplankton community structure. Multi-year surveys reveal that the dominant phytoplankton species in Daihai Lake have shifted from diatoms and green algae to cyanobacteria and cryptophytes. This study uncovers the key mechanisms driving seasonal succession in phytoplankton communities of northern cold-arid lakes, providing a scientific basis for ecological management and conservation of Daihai Lake.
Phytoplankton, as the primary producers in lake ecosystems, influence material cycling and energy flow within water bodies. Their community structure and dynamic changes directly reflect the nutrient status and ecological health of the water body. To comprehensively understand phytoplankton variations and influencing factors in tailwater lakes of northern arid-cold regions, the representative Daihai Lake was selected as the study site. Water and sediment samples were collected across all four seasons in 2024 to systematically analyse phytoplankton community structure and its response to environmental factors. Results indicate that during the study period, water body total nitrogen (TN) and total phosphorus (TP) concentrations exceeded Class V and Class IV water standards, respectively, while sediment TN and TP contents surpassed the national sediment average. A total of 95 phytoplankton species belonging to 8 phyla were identified, dominated by Chlorophyta, Cyanobacteria, and Diatomeae. Phytoplankton cell density, biomass, and Chl.a concentration peaked in winter. Ten dominant species across 5 phyla were identified, primarily from Chlorophyta and Diatomeae, with Microcystis and Chromomonas serving as key dominant species throughout the year. Results from Shannon diversity index, Pielou evenness index, Margalef richness index, and Simpson dominance index indicated higher phytoplankton community diversity and greater ecosystem stability in spring and summer compared to autumn and winter. Phytoplankton communities in Daihai Lake exhibited low spatial heterogeneity, suggesting that diversity and richness are primarily influenced by seasonal variations. Statistical analysis indicates that water temperature (WT), pH, dissolved oxygen (DO), total nitrogen (TN), and dissolved inorganic phosphorus (DIP) are key factors influencing phytoplankton community structure. Multi-year surveys reveal that the dominant phytoplankton species in Daihai Lake have shifted from diatoms and green algae to cyanobacteria and cryptophytes. This study uncovers the key mechanisms driving seasonal succession in phytoplankton communities of northern cold-arid lakes, providing a scientific basis for ecological management and conservation of Daihai Lake.
Xu Hai, Lian Gang, Wu Zhixu, Zhu Mengyuan, Li Huiyun, Shi Kun, Zhang Yunlin, Qin Boqiang, Zhu Guangwei
Available online: April 13, 2026
Abstract:
Reservoirs, as a type of artificial lake, have their number and controlled water volume in China approaching that of natural lakes, making them an important component of China"s surface-based manageable static water resources. The hydrological processes, topography, and management/utilization patterns of reservoirs differ from those of natural lakes. Ecologically, reservoirs exhibit characteristics of both riverine and lake ecosystems, and their limnological mechanisms are unique. Establishing scientific observation field stations to conduct long-term ecological monitoring, in-situ experimental research, and the development of restoration technologies for reservoirs is of great significance for scientifically supporting the ecological and environmental security of reservoirs and the sustainable use of their resources. Taking the Qiandaohu Ecosystem Research Station of the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences (referred to as the "Qiandaohu Ecological Station") as an example, this paper analyzes the achievements, hotspots, and challenges in the ecological research of large deep-water reservoirs based on 20 years of scientific observation, experimental research, and technology demonstration on the water environment and aquatic ecosystem of Qiandaohu Reservoir. Monitoring of water quality and ecological indicators at the Qiandaohu Ecosystem Research Station over the past five years indicates that the overall water quality of Qiandaohu Reservoir remains stable at an oligotrophic to mesotrophic state. However, key water quality monitoring sections still face risks such as unstable water quality and abnormal algal proliferation in local areas. Stratification of ecological and environmental indicators, such as thermal stratification, is evident, with significant seasonal variations and interannual fluctuations. Research shows that meteorological and hydrological events, such as warming, heavy precipitation events, and high-temperature droughts, have substantial impacts on the water quality and ecology of Qiandaohu Reservoir. Human activities, including changes in watershed land use and reservoir fishery management models, also profoundly affect the water quality and aquatic ecology of Qiandaohu Reservoir. Furthermore, technologies developed at the Qiandaohu Ecosystem Research Station, such as reservoir monitoring, water quality and algal bloom early warning, and ecological restoration of the reservoir, offer significant demonstration value for the ecological and environmental protection of similar source water reservoirs in China. Current research priorities for the Qiandaohu Reservoir aquatic ecosystem include integrated technologies for ensuring water quality safety in source water reservoirs, mechanisms of physical environmental changes (e.g., light, heat, and hydrodynamic processes) in reservoirs and their ecological effects, food web structures and ecological regulation technologies in large reservoirs, carbon cycling and greenhouse gas emission mechanisms in deep-water reservoirs, and digital twin and AI-based intelligent management technologies for reservoir water environments.
Reservoirs, as a type of artificial lake, have their number and controlled water volume in China approaching that of natural lakes, making them an important component of China"s surface-based manageable static water resources. The hydrological processes, topography, and management/utilization patterns of reservoirs differ from those of natural lakes. Ecologically, reservoirs exhibit characteristics of both riverine and lake ecosystems, and their limnological mechanisms are unique. Establishing scientific observation field stations to conduct long-term ecological monitoring, in-situ experimental research, and the development of restoration technologies for reservoirs is of great significance for scientifically supporting the ecological and environmental security of reservoirs and the sustainable use of their resources. Taking the Qiandaohu Ecosystem Research Station of the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences (referred to as the "Qiandaohu Ecological Station") as an example, this paper analyzes the achievements, hotspots, and challenges in the ecological research of large deep-water reservoirs based on 20 years of scientific observation, experimental research, and technology demonstration on the water environment and aquatic ecosystem of Qiandaohu Reservoir. Monitoring of water quality and ecological indicators at the Qiandaohu Ecosystem Research Station over the past five years indicates that the overall water quality of Qiandaohu Reservoir remains stable at an oligotrophic to mesotrophic state. However, key water quality monitoring sections still face risks such as unstable water quality and abnormal algal proliferation in local areas. Stratification of ecological and environmental indicators, such as thermal stratification, is evident, with significant seasonal variations and interannual fluctuations. Research shows that meteorological and hydrological events, such as warming, heavy precipitation events, and high-temperature droughts, have substantial impacts on the water quality and ecology of Qiandaohu Reservoir. Human activities, including changes in watershed land use and reservoir fishery management models, also profoundly affect the water quality and aquatic ecology of Qiandaohu Reservoir. Furthermore, technologies developed at the Qiandaohu Ecosystem Research Station, such as reservoir monitoring, water quality and algal bloom early warning, and ecological restoration of the reservoir, offer significant demonstration value for the ecological and environmental protection of similar source water reservoirs in China. Current research priorities for the Qiandaohu Reservoir aquatic ecosystem include integrated technologies for ensuring water quality safety in source water reservoirs, mechanisms of physical environmental changes (e.g., light, heat, and hydrodynamic processes) in reservoirs and their ecological effects, food web structures and ecological regulation technologies in large reservoirs, carbon cycling and greenhouse gas emission mechanisms in deep-water reservoirs, and digital twin and AI-based intelligent management technologies for reservoir water environments.
Available online: April 13, 2026
Abstract:
Fatty acids are key biomarkers that act as essential energy substrates and structural components for aquatic organisms while displaying conserved, taxon-specific profiles across primary producer groups, making them effective tracers of nutritional sources and energy flow in aquatic ecosystems. Zooplankton, as critical links between primary producers and higher trophic levels, exhibit fatty acid compositions that reflect dietary quality and utilization efficiency, thereby governing the ecological efficiency of energy transfer to upper food webs. Lake Erhai, the second-largest plateau freshwater lake in Yunnan Province, China, has experienced increasing eutrophication and frequent cyanobacterial blooms in recent years, yet studies on zooplankton fatty acids in this lake remain limited. To examine seasonal variation in zooplankton fatty acid composition and its environmental drivers, four dominant species—Mesocyclops leuckarti, Daphnia galeata, Phyllodiaptomus tunguidus, and Bosmina longirostris—were collected monthly from July to October 2025 at five sampling sites in Lake Erhai. Fatty acids were analyzed by gas chromatography–mass spectrometry (GC–MS), and permutational multivariate analysis of variance (PERMANOVA), similarity percentage analysis (SIMPER), and redundancy analysis (RDA) were used to evaluate the effects of month, species, site, and environmental variables. Results indicated that: (1) month was the primary factor shaping fatty acid composition, accounting for 40.93% of variance (PERMANOVA, F=25.827, P<0.0001), with no significant main effects of species (R2=0.035, P=0.195) or site (R2=0.059, P=0.082); (2) phytoplankton community composition strongly influenced particulate organic matter (POM) fatty acid quality, with diatoms (especially Cyclotella) and Cryptomonas positively correlated with polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (ARA); (3) variance partitioning showed that POM fatty acids and environmental variables together explained 54.25% of zooplankton fatty acid variance, with pure effects of 28.43% (P=0.001) and 14.28% (P=0.006), respectively, and water temperature as the most influential single factor (R2=0.141, P=0.001); (4) SIMPER analysis revealed that declining water temperature significantly increased zooplankton polyunsaturated fatty acid (PUFA) abundance, with EPA rising from 3.78% in July to 7.86% in October and ARA from 3.41% in September to 9.51% in October, while saturated fatty acids (stearic acid, 18:0; palmitic acid, 16:0) decreased; (5) a temporal lag existed between peak fatty acid quality in POM and zooplankton: POM PUFA peaked at 60.22% in September and fell to 34.68% in October, whereas zooplankton EPA and ARA peaked in October, indicating delayed trophic transfer. These findings clarify seasonal dynamics and drivers of zooplankton fatty acids in a eutrophic plateau lake, providing a scientific basis for understanding nutrient transfer mechanisms in lake food webs.
Fatty acids are key biomarkers that act as essential energy substrates and structural components for aquatic organisms while displaying conserved, taxon-specific profiles across primary producer groups, making them effective tracers of nutritional sources and energy flow in aquatic ecosystems. Zooplankton, as critical links between primary producers and higher trophic levels, exhibit fatty acid compositions that reflect dietary quality and utilization efficiency, thereby governing the ecological efficiency of energy transfer to upper food webs. Lake Erhai, the second-largest plateau freshwater lake in Yunnan Province, China, has experienced increasing eutrophication and frequent cyanobacterial blooms in recent years, yet studies on zooplankton fatty acids in this lake remain limited. To examine seasonal variation in zooplankton fatty acid composition and its environmental drivers, four dominant species—Mesocyclops leuckarti, Daphnia galeata, Phyllodiaptomus tunguidus, and Bosmina longirostris—were collected monthly from July to October 2025 at five sampling sites in Lake Erhai. Fatty acids were analyzed by gas chromatography–mass spectrometry (GC–MS), and permutational multivariate analysis of variance (PERMANOVA), similarity percentage analysis (SIMPER), and redundancy analysis (RDA) were used to evaluate the effects of month, species, site, and environmental variables. Results indicated that: (1) month was the primary factor shaping fatty acid composition, accounting for 40.93% of variance (PERMANOVA, F=25.827, P<0.0001), with no significant main effects of species (R2=0.035, P=0.195) or site (R2=0.059, P=0.082); (2) phytoplankton community composition strongly influenced particulate organic matter (POM) fatty acid quality, with diatoms (especially Cyclotella) and Cryptomonas positively correlated with polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (ARA); (3) variance partitioning showed that POM fatty acids and environmental variables together explained 54.25% of zooplankton fatty acid variance, with pure effects of 28.43% (P=0.001) and 14.28% (P=0.006), respectively, and water temperature as the most influential single factor (R2=0.141, P=0.001); (4) SIMPER analysis revealed that declining water temperature significantly increased zooplankton polyunsaturated fatty acid (PUFA) abundance, with EPA rising from 3.78% in July to 7.86% in October and ARA from 3.41% in September to 9.51% in October, while saturated fatty acids (stearic acid, 18:0; palmitic acid, 16:0) decreased; (5) a temporal lag existed between peak fatty acid quality in POM and zooplankton: POM PUFA peaked at 60.22% in September and fell to 34.68% in October, whereas zooplankton EPA and ARA peaked in October, indicating delayed trophic transfer. These findings clarify seasonal dynamics and drivers of zooplankton fatty acids in a eutrophic plateau lake, providing a scientific basis for understanding nutrient transfer mechanisms in lake food webs.
Available online: April 13, 2026
Abstract:
The operation of cascade reservoirs has a significant impact on river water temperature. This study constructs a quantitative attribution framework to distinguish the impacts of climate change and reservoir operation on river water temperature by integrating the Maximal Overlap Discrete Wavelet Transform (MODWT), Multiresolution Analysis (MRA), ERA5-Land reanalysis data, and a Bi-LSTM model. Taking the Xiangjiaba Station in the lower Jinsha River as a case study, the multi-scale effects of cascade reservoir operation on water temperature were investigated. The results indicate that: (1) The joint operation of the cascade reservoirs significantly dampens water temperature fluctuations at medium-to-high frequencies (daily, weekly, monthly scales), exhibiting a "smoothing effect"; (2) At low frequencies (seasonal and inter-annual scales), reservoir operation leads to a significant "attenuation effect" and "lag effect" on water temperature, and these effects intensify with an increasing number of reservoirs in operation; (3) Reservoir operation is the dominant factor driving water temperature changes at the seasonal scale, while climate change primarily drives the changes at the annual scale during the four-reservoir joint operation period. This study reveals the multi-temporal scale characteristics of the impact of cascade reservoirs on water temperature, proposes a novel attribution analysis method, and provides a scientific basis for the ecological operation of reservoirs and watershed water temperature management.
The operation of cascade reservoirs has a significant impact on river water temperature. This study constructs a quantitative attribution framework to distinguish the impacts of climate change and reservoir operation on river water temperature by integrating the Maximal Overlap Discrete Wavelet Transform (MODWT), Multiresolution Analysis (MRA), ERA5-Land reanalysis data, and a Bi-LSTM model. Taking the Xiangjiaba Station in the lower Jinsha River as a case study, the multi-scale effects of cascade reservoir operation on water temperature were investigated. The results indicate that: (1) The joint operation of the cascade reservoirs significantly dampens water temperature fluctuations at medium-to-high frequencies (daily, weekly, monthly scales), exhibiting a "smoothing effect"; (2) At low frequencies (seasonal and inter-annual scales), reservoir operation leads to a significant "attenuation effect" and "lag effect" on water temperature, and these effects intensify with an increasing number of reservoirs in operation; (3) Reservoir operation is the dominant factor driving water temperature changes at the seasonal scale, while climate change primarily drives the changes at the annual scale during the four-reservoir joint operation period. This study reveals the multi-temporal scale characteristics of the impact of cascade reservoirs on water temperature, proposes a novel attribution analysis method, and provides a scientific basis for the ecological operation of reservoirs and watershed water temperature management.
Available online: April 08, 2026
Abstract:
In order to reveal the distribution patterns and causes of microplastics (MPs) in the surface water of plateau lakes with different degrees of human interference, this study selected Shudu Lake, which has relatively weak human interference, and Xingyun Lake, which has relatively strong human interference, as the research areas. Through sample collection and the separation, extraction, and identification of MPs, the distribution characteristics and source differences of MPs in the surface water of the two lakes were compared and analyzed, providing a theoretical basis for the prevention and protection restoration of MPs in different plateau lakes. The results indicate that: (1) The average abundance of MPs was 1.82 particles/m3 in Shudu Lake and 2.14 ± 1.25 particles/m3 in Xingyun Lake. The average number of MPs was 478 ± 57 particles/individual in Shudu Lake and 558 ± 314 particles/individual in Xingyun Lake. As the intensity of human disturbance increases, both the average abundance and average count of MPs in the surface waters of these two plateau lakes show a gradual upward trend. (2) The MPs in Shudu Lake are mainly black and blue (with an average total count of 295 ± 12 particles/individual), while those in Xingyun Lake are mainly blue and black (with an average total count of 403 ± 106 particles/individual). The shapes of MPs in both Xingyun Lake and Shudu Lake are mainly line, with an average number of 462 particles/individual in Shudu Lake and 481 ± 239 particles/individual in Xingyun Lake. The average number of MPs with a size of ≤ 200 μm is 86 ± 30 particles/individual in Shudu Lake and 280 ± 167 particles/individual in Xingyun Lake. The main polymer types in Shudu Lake are 4 types (rayon (RY), polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET)), while in Xingyun Lake there are 7 types (RY, PE, PET, low-density styrene-butadiene-styrene (SBS), polyethylenimine ephchlorohydrin modified (PEM), polyester (PES), and polyvinyl alcohol (PVA)). Shudu Lake has fewer polymer types than Xingyun Lake, indicating that the sources of MPs in Xingyun Lake are more diverse. With the increase in the intensity of human interference, the average quantities of the main colors (black and blue), main shapes (line), and size range (≤ 200 μm) of MPs in the surface water of the two plateau lakes have all shown a gradual increase trend, and the number of main polymer types has also shown a gradual increase trend. (3) Shudu Lake is oligotrophic and subject to limited anthropogenic disturbance; the main sources of microplastic pollution are tourism activities, grazing, and atmospheric deposition. Xingyun Lake is mildly eutrophic and experiences stronger human interference; MPs pollution originates from domestic sewage, agricultural cultivation, transportation, fish farming, fishing operations, industrial production, tourism activities, atmospheric deposition, and grazing activities. The distribution and sources of MPs in the surface waters of the two plateau lakes differ, and the level of anthropogenic disturbance is the key factor determining MPs abundance.
In order to reveal the distribution patterns and causes of microplastics (MPs) in the surface water of plateau lakes with different degrees of human interference, this study selected Shudu Lake, which has relatively weak human interference, and Xingyun Lake, which has relatively strong human interference, as the research areas. Through sample collection and the separation, extraction, and identification of MPs, the distribution characteristics and source differences of MPs in the surface water of the two lakes were compared and analyzed, providing a theoretical basis for the prevention and protection restoration of MPs in different plateau lakes. The results indicate that: (1) The average abundance of MPs was 1.82 particles/m3 in Shudu Lake and 2.14 ± 1.25 particles/m3 in Xingyun Lake. The average number of MPs was 478 ± 57 particles/individual in Shudu Lake and 558 ± 314 particles/individual in Xingyun Lake. As the intensity of human disturbance increases, both the average abundance and average count of MPs in the surface waters of these two plateau lakes show a gradual upward trend. (2) The MPs in Shudu Lake are mainly black and blue (with an average total count of 295 ± 12 particles/individual), while those in Xingyun Lake are mainly blue and black (with an average total count of 403 ± 106 particles/individual). The shapes of MPs in both Xingyun Lake and Shudu Lake are mainly line, with an average number of 462 particles/individual in Shudu Lake and 481 ± 239 particles/individual in Xingyun Lake. The average number of MPs with a size of ≤ 200 μm is 86 ± 30 particles/individual in Shudu Lake and 280 ± 167 particles/individual in Xingyun Lake. The main polymer types in Shudu Lake are 4 types (rayon (RY), polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET)), while in Xingyun Lake there are 7 types (RY, PE, PET, low-density styrene-butadiene-styrene (SBS), polyethylenimine ephchlorohydrin modified (PEM), polyester (PES), and polyvinyl alcohol (PVA)). Shudu Lake has fewer polymer types than Xingyun Lake, indicating that the sources of MPs in Xingyun Lake are more diverse. With the increase in the intensity of human interference, the average quantities of the main colors (black and blue), main shapes (line), and size range (≤ 200 μm) of MPs in the surface water of the two plateau lakes have all shown a gradual increase trend, and the number of main polymer types has also shown a gradual increase trend. (3) Shudu Lake is oligotrophic and subject to limited anthropogenic disturbance; the main sources of microplastic pollution are tourism activities, grazing, and atmospheric deposition. Xingyun Lake is mildly eutrophic and experiences stronger human interference; MPs pollution originates from domestic sewage, agricultural cultivation, transportation, fish farming, fishing operations, industrial production, tourism activities, atmospheric deposition, and grazing activities. The distribution and sources of MPs in the surface waters of the two plateau lakes differ, and the level of anthropogenic disturbance is the key factor determining MPs abundance.
Available online: March 31, 2026
Abstract:
Accurate prediction of sediment concentration processes is crucial for effective reservoir flood regulation, sediment management, and ecological conservation in river basins with significant sediment loads, such as the Yellow River. The ability to predict sediment concentrations accurately is key to mitigating the negative impacts of sedimentation in reservoirs, optimizing flood control, and ensuring the safety of infrastructure and water quality management. In this study, we focus on the sediment concentration process at the Tongguan Hydrological Station, which is located in the middle and lower reaches of the Yellow River. The Yellow River, known for its high sediment load, plays a vital role in the sediment transport dynamics that influence the river"s water quality and sedimentation patterns. The Tongguan station is a critical monitoring point in the Yellow River basin because it marks the confluence of the Yellow River mainstream with major tributaries such as the Weihe and Beiluohe Rivers, and it is located just before sediment enters the Sanmenxia Reservoir, which significantly influences downstream sedimentation and flood management. This study proposes a Parallel Spatio-Temporal Attention Long Short-Term Memory (PSTA-LSTM) model designed for sediment concentration forecasting, specifically tailored to handle the dynamic and complex flow-sediment conditions of the Yellow River. The PSTA-LSTM model integrates a parallel spatio-temporal attention mechanism that allows it to jointly capture multiscale temporal dependencies and spatial correlations among different watershed sites, significantly improving its ability to model sediment transport processes. In addition, the model incorporates an adaptive segmented rectified linear unit (SReLU) in the hidden layers to enhance the model’s capacity to learn complex nonlinear features and better handle rapid fluctuations in sediment concentrations, particularly during peak sediment events. This adaptive function helps the model manage the large variability in sediment loads commonly observed in rivers like the Yellow River, which is subject to varying flow conditions, tributary contributions, and local erosion-deposition dynamics. Experiments were conducted using measured hydrological and sediment data from 2000 to 2024. The results show that compared to the traditional serial LSTM structure, introducing the parallel spatio-temporal attention mechanism reduces the overall Root Mean Square Error (RMSE) by approximately 25.6%, and improves Peak Sediment Prediction Accuracy (PRE) by about 12.7%. Incorporating the SReLU activation function significantly enhances peak prediction accuracy, with the Nash-Sutcliffe Efficiency (NSE) improving by over 9%, showing that SReLU can more effectively handle peak sediment values. The study focuses on the sediment concentration process at the Tongguan hydrological station, located in the confluence area of the middle Yellow River. Tongguan Station is situated at the junction of the Yellow River mainstream and major tributaries such as the Weihe and Beiluohe Rivers. It serves as a critical sediment control section before the Yellow River enters the Sanmenxia Reservoir, playing an important role in reservoir regulation and downstream sediment transport. The upstream water and sediment mainly originate from the Yellow River basin above the Longmen Station, as well as the Weihe River basin at Huaxian Station and the Beiluohe River basin at Zhuangtou Station. Among these, the mainstream floods are characterized by sharp rises and falls with high sediment concentration; the Weihe River floods have a longer duration and a more blunt peak, while the Beiluohe River floods have sharp, narrow peaks, high sediment concentration, and rapid sediment wave propagation. The confluence and superposition of floods from different sources at the Tongguan confluence area not only affect sediment transport intensity but also determine the temporal variation characteristics of the sediment concentration process at Tongguan Station. Experiments were conducted using long-term observed hydrological and sediment data from 2000 to 2024, with the samples classified into five flow-sediment regimes: high-flow/high-sediment, medium-flow/medium-sediment, low-flow/low-sediment, high-flow/low-sediment, and low-flow/high-sediment. The PSTA-LSTM model was trained and evaluated separately under each regime and further compared between flood and non-flood seasons to examine its adaptability to varying hydrological conditions. The results show that introducing the parallel spatio-temporal attention mechanism improves the model’s performance significantly, with the Root Mean Square Error (RMSE) decreasing by approximately 25.6% and Peak Sediment Prediction Accuracy (PRE) improving by about 12.7%. Additionally, incorporating the SReLU activation function led to an increase in Nash-Sutcliffe Efficiency (NSE) by 6-11% compared to the traditional ReLU and softplus activation functions, showing its enhanced capability to handle peak sediment values effectively. The results also demonstrate that regime-based training based on flow-sediment types improves the prediction accuracy, with RMSE decreasing by approximately 15.7%, and NSE reaching over 80%. The comparison between flood and non-flood seasons shows that the PSTA-LSTM model exhibits stronger responsiveness during the flood season, especially during periods with significant peak sediment concentrations and rapid short-term fluctuations. These results highlight the model"s ability to adapt to dynamic and complex sediment transport conditions and its potential for real-time sediment concentration forecasting in large river systems like the Yellow River.
Accurate prediction of sediment concentration processes is crucial for effective reservoir flood regulation, sediment management, and ecological conservation in river basins with significant sediment loads, such as the Yellow River. The ability to predict sediment concentrations accurately is key to mitigating the negative impacts of sedimentation in reservoirs, optimizing flood control, and ensuring the safety of infrastructure and water quality management. In this study, we focus on the sediment concentration process at the Tongguan Hydrological Station, which is located in the middle and lower reaches of the Yellow River. The Yellow River, known for its high sediment load, plays a vital role in the sediment transport dynamics that influence the river"s water quality and sedimentation patterns. The Tongguan station is a critical monitoring point in the Yellow River basin because it marks the confluence of the Yellow River mainstream with major tributaries such as the Weihe and Beiluohe Rivers, and it is located just before sediment enters the Sanmenxia Reservoir, which significantly influences downstream sedimentation and flood management. This study proposes a Parallel Spatio-Temporal Attention Long Short-Term Memory (PSTA-LSTM) model designed for sediment concentration forecasting, specifically tailored to handle the dynamic and complex flow-sediment conditions of the Yellow River. The PSTA-LSTM model integrates a parallel spatio-temporal attention mechanism that allows it to jointly capture multiscale temporal dependencies and spatial correlations among different watershed sites, significantly improving its ability to model sediment transport processes. In addition, the model incorporates an adaptive segmented rectified linear unit (SReLU) in the hidden layers to enhance the model’s capacity to learn complex nonlinear features and better handle rapid fluctuations in sediment concentrations, particularly during peak sediment events. This adaptive function helps the model manage the large variability in sediment loads commonly observed in rivers like the Yellow River, which is subject to varying flow conditions, tributary contributions, and local erosion-deposition dynamics. Experiments were conducted using measured hydrological and sediment data from 2000 to 2024. The results show that compared to the traditional serial LSTM structure, introducing the parallel spatio-temporal attention mechanism reduces the overall Root Mean Square Error (RMSE) by approximately 25.6%, and improves Peak Sediment Prediction Accuracy (PRE) by about 12.7%. Incorporating the SReLU activation function significantly enhances peak prediction accuracy, with the Nash-Sutcliffe Efficiency (NSE) improving by over 9%, showing that SReLU can more effectively handle peak sediment values. The study focuses on the sediment concentration process at the Tongguan hydrological station, located in the confluence area of the middle Yellow River. Tongguan Station is situated at the junction of the Yellow River mainstream and major tributaries such as the Weihe and Beiluohe Rivers. It serves as a critical sediment control section before the Yellow River enters the Sanmenxia Reservoir, playing an important role in reservoir regulation and downstream sediment transport. The upstream water and sediment mainly originate from the Yellow River basin above the Longmen Station, as well as the Weihe River basin at Huaxian Station and the Beiluohe River basin at Zhuangtou Station. Among these, the mainstream floods are characterized by sharp rises and falls with high sediment concentration; the Weihe River floods have a longer duration and a more blunt peak, while the Beiluohe River floods have sharp, narrow peaks, high sediment concentration, and rapid sediment wave propagation. The confluence and superposition of floods from different sources at the Tongguan confluence area not only affect sediment transport intensity but also determine the temporal variation characteristics of the sediment concentration process at Tongguan Station. Experiments were conducted using long-term observed hydrological and sediment data from 2000 to 2024, with the samples classified into five flow-sediment regimes: high-flow/high-sediment, medium-flow/medium-sediment, low-flow/low-sediment, high-flow/low-sediment, and low-flow/high-sediment. The PSTA-LSTM model was trained and evaluated separately under each regime and further compared between flood and non-flood seasons to examine its adaptability to varying hydrological conditions. The results show that introducing the parallel spatio-temporal attention mechanism improves the model’s performance significantly, with the Root Mean Square Error (RMSE) decreasing by approximately 25.6% and Peak Sediment Prediction Accuracy (PRE) improving by about 12.7%. Additionally, incorporating the SReLU activation function led to an increase in Nash-Sutcliffe Efficiency (NSE) by 6-11% compared to the traditional ReLU and softplus activation functions, showing its enhanced capability to handle peak sediment values effectively. The results also demonstrate that regime-based training based on flow-sediment types improves the prediction accuracy, with RMSE decreasing by approximately 15.7%, and NSE reaching over 80%. The comparison between flood and non-flood seasons shows that the PSTA-LSTM model exhibits stronger responsiveness during the flood season, especially during periods with significant peak sediment concentrations and rapid short-term fluctuations. These results highlight the model"s ability to adapt to dynamic and complex sediment transport conditions and its potential for real-time sediment concentration forecasting in large river systems like the Yellow River.
Li Qiao, Wang Xiaoxiao, Yi Xuemei, Ma Xiaoling, Cai Yunlong, Wu Tianyou, Yang Nairui, Li Dasong, Wu Shengjun
Available online: March 31, 2026
Abstract:
The spatial distribution patterns, phenotypic responses, and environmental driving mechanisms of dominant plants in the riparian zone of large reservoirs are key to understanding plant adaptation mechanisms and the community succession to the alternating terrestrial and aquatic habitats. This study focuses on Cynodon dactylon (L.) Pers.), a typical dominant plant in the drawdown zone of the Three Gorges Reservoir.. Through comprehensive vegetation and soil surveys, and using methods such as spatial interpolation, analysis of variance, and regression analysis, we analyzed its spatial distribution, phenotypic variation, and environmental drivers. The results showed that the coverage of C. dactylon exhibited a horizontal spatial pattern, characterized as high in the mid-section yet low in both the upper and lower sections of the reservoir. with its coverage and density in the mainstream significantly lower than in the tributaries. Along the elevation gradient, both the coverage and density of C. dactylon in the 165–175 m elevation zone were significantly lower. Analysis of environmental factors revealed that the coverage and density were primarily regulated by soil bulk density and phosphorus content, while high nitrogen environments drove preferential biomass investment into leaves to enhance photosynthetic capacity. The study demonstrates that C. dactylon adapts to environmental heterogeneity in the hydro-fluctuation zone by adjusting biomass allocation strategies and exhibiting phenotypic plasticity, providing a theoretical basis for near-natural restoration of reservoir riparian zones.
The spatial distribution patterns, phenotypic responses, and environmental driving mechanisms of dominant plants in the riparian zone of large reservoirs are key to understanding plant adaptation mechanisms and the community succession to the alternating terrestrial and aquatic habitats. This study focuses on Cynodon dactylon (L.) Pers.), a typical dominant plant in the drawdown zone of the Three Gorges Reservoir.. Through comprehensive vegetation and soil surveys, and using methods such as spatial interpolation, analysis of variance, and regression analysis, we analyzed its spatial distribution, phenotypic variation, and environmental drivers. The results showed that the coverage of C. dactylon exhibited a horizontal spatial pattern, characterized as high in the mid-section yet low in both the upper and lower sections of the reservoir. with its coverage and density in the mainstream significantly lower than in the tributaries. Along the elevation gradient, both the coverage and density of C. dactylon in the 165–175 m elevation zone were significantly lower. Analysis of environmental factors revealed that the coverage and density were primarily regulated by soil bulk density and phosphorus content, while high nitrogen environments drove preferential biomass investment into leaves to enhance photosynthetic capacity. The study demonstrates that C. dactylon adapts to environmental heterogeneity in the hydro-fluctuation zone by adjusting biomass allocation strategies and exhibiting phenotypic plasticity, providing a theoretical basis for near-natural restoration of reservoir riparian zones.
Available online: March 19, 2026
Abstract:
This study investigated five typical wetland plants in Dongting Lake—Acorus calamus, Zizania latifolia, Phragmites australis, Carex brevicuspis, and Typha orientalis—under different flooding durations (30, 60, 90, and 120 days), systematically analyzing their morphological and physiological responses as well as nitrogen and phosphorus removal efficiency. The results showed that flooding duration significantly influenced plant morphology, physiological responses, and nutrient removal efficiency. Morphologically, with increasing flooding time, the biomass and plant height of A. calamus decreased significantly; the biomass and root length of C. brevicuspis remained relatively stable while plant height slightly decreased; whereas the plant heights of P. australis, Z. latifolia, and T. orientalis continued to increase with prolonged flooding. Physiologically, markers of oxidative stress and osmoregulation showed species-specific trends. For instance, in Z. latifolia, contents of malondialdehyde (MDA) and soluble sugars decreased significantly, while antioxidant enzyme activity and chlorophyll content increased. In contrast, T. orientalis displayed a dynamic change in MDA, superoxide dismutase (SOD), and proline, which decreased initially, peaked at 90 days, and then declined again, whereas its chlorophyll content continuously decreased. Regarding purification capacity, the nitrogen and phosphorus removal rates of P. australis and T. orientalis continuously improved with prolonged flooding. In contrast, A. calamus, Z. latifolia, and C. brevicuspis reached peak removal efficiency at 60–90 days of treatment before declining. In summary, different plants exhibited significant species-specific and time-dependent responses in morphology, physiology, and function under flooding conditions. P. australis and T. orientalis can maintain high purification efficiency under prolonged flooding, making them more suitable as dominant species for long-term flooded wetland ecosystems.
This study investigated five typical wetland plants in Dongting Lake—Acorus calamus, Zizania latifolia, Phragmites australis, Carex brevicuspis, and Typha orientalis—under different flooding durations (30, 60, 90, and 120 days), systematically analyzing their morphological and physiological responses as well as nitrogen and phosphorus removal efficiency. The results showed that flooding duration significantly influenced plant morphology, physiological responses, and nutrient removal efficiency. Morphologically, with increasing flooding time, the biomass and plant height of A. calamus decreased significantly; the biomass and root length of C. brevicuspis remained relatively stable while plant height slightly decreased; whereas the plant heights of P. australis, Z. latifolia, and T. orientalis continued to increase with prolonged flooding. Physiologically, markers of oxidative stress and osmoregulation showed species-specific trends. For instance, in Z. latifolia, contents of malondialdehyde (MDA) and soluble sugars decreased significantly, while antioxidant enzyme activity and chlorophyll content increased. In contrast, T. orientalis displayed a dynamic change in MDA, superoxide dismutase (SOD), and proline, which decreased initially, peaked at 90 days, and then declined again, whereas its chlorophyll content continuously decreased. Regarding purification capacity, the nitrogen and phosphorus removal rates of P. australis and T. orientalis continuously improved with prolonged flooding. In contrast, A. calamus, Z. latifolia, and C. brevicuspis reached peak removal efficiency at 60–90 days of treatment before declining. In summary, different plants exhibited significant species-specific and time-dependent responses in morphology, physiology, and function under flooding conditions. P. australis and T. orientalis can maintain high purification efficiency under prolonged flooding, making them more suitable as dominant species for long-term flooded wetland ecosystems.
Available online: March 19, 2026
Abstract:
Under global warming, the increasing frequency of high-temperature events in lakes, combined with the implementation of the "Cessation of Aquaculture and Return to Lake" ecological restoration project in the eastern Lake Taihu region since 2019, has created complex interactions that complicate the dynamic processes of methane (CH4) emissions from lakes. This study aims to elucidate the impacts of high-temperature events and ecological restoration on CH4 emissions in Lake Taihu and their underlying mechanisms. Based on high-frequency observational data from the Dongtaihu site of the Taihu Eddy Flux Network from 2018 to 2020, the seasonal threshold method was employed to identify high-temperature events, and their effects on CH4 fluxes, as well as the regulatory effects of the "Cessation of Aquaculture and Return to Lake" project, were systematically analyzed. The results indicated that the seasonal threshold method effectively captured short-term high-temperature processes driving CH4 emissions, accommodating seasonal water-temperature fluctuations and high-frequency temporal variations in CH4 emissions. A total of 23 high-temperature events were identified from 2018 to 2020. The promoting effect of high-temperature events on CH4 emissions showed clear seasonal differences, being stronger in spring and autumn than in summer and winter. During individual events, CH4 fluxes typically exhibited a three-phase pattern: remaining stable in the pre-heatwave period, increasing sharply during the heatwave, and decreasing in the post-heatwave period. The "Cessation of Aquaculture and Return to Lake" project effectively suppressed CH4 emissions during high-temperature periods. During the ecological restoration period, the median CH4 fluxes before, during, and after high-temperature events were 0.05–0.17, 0.07–0.25, and 0.04–0.15 μg·m?2·s?1, respectively, representing reductions of approximately 72%–95% compared to the aquaculture period (0.42–0.62, 1.05–5.26, and 0.71–4.60 μg·m?2·s?1, respectively). This study provides a theoretical basis for understanding the response mechanisms of carbon cycling in shallow lakes to climate warming and ecological management.
Under global warming, the increasing frequency of high-temperature events in lakes, combined with the implementation of the "Cessation of Aquaculture and Return to Lake" ecological restoration project in the eastern Lake Taihu region since 2019, has created complex interactions that complicate the dynamic processes of methane (CH4) emissions from lakes. This study aims to elucidate the impacts of high-temperature events and ecological restoration on CH4 emissions in Lake Taihu and their underlying mechanisms. Based on high-frequency observational data from the Dongtaihu site of the Taihu Eddy Flux Network from 2018 to 2020, the seasonal threshold method was employed to identify high-temperature events, and their effects on CH4 fluxes, as well as the regulatory effects of the "Cessation of Aquaculture and Return to Lake" project, were systematically analyzed. The results indicated that the seasonal threshold method effectively captured short-term high-temperature processes driving CH4 emissions, accommodating seasonal water-temperature fluctuations and high-frequency temporal variations in CH4 emissions. A total of 23 high-temperature events were identified from 2018 to 2020. The promoting effect of high-temperature events on CH4 emissions showed clear seasonal differences, being stronger in spring and autumn than in summer and winter. During individual events, CH4 fluxes typically exhibited a three-phase pattern: remaining stable in the pre-heatwave period, increasing sharply during the heatwave, and decreasing in the post-heatwave period. The "Cessation of Aquaculture and Return to Lake" project effectively suppressed CH4 emissions during high-temperature periods. During the ecological restoration period, the median CH4 fluxes before, during, and after high-temperature events were 0.05–0.17, 0.07–0.25, and 0.04–0.15 μg·m?2·s?1, respectively, representing reductions of approximately 72%–95% compared to the aquaculture period (0.42–0.62, 1.05–5.26, and 0.71–4.60 μg·m?2·s?1, respectively). This study provides a theoretical basis for understanding the response mechanisms of carbon cycling in shallow lakes to climate warming and ecological management.
Available online: March 19, 2026
Abstract:
The Yarlung Tsangpo River is one of the world"s major international rivers and also one of the most sensitive and fragile ecosystems globally. Eukaryotic phytoplankton play a vital role in maintaining the ecological balance of this river ecosystem. To reveal the diversity, spatiotemporal distribution characteristics, and key driving factors of eukaryotic phytoplankton communities in the Nyang River and Palong Tsangpo, representative primary tributaries of the lower Yarlung Tsangpo River, this study employed high-throughput amplicon sequencing technology to investigate the diversity patterns and driving factors of eukaryotic phytoplankton across three seasons spring, summer, and autumn—in this watershed. Results revealed that 6,723 ASVs of eukaryotic phytoplankton were identified across the three seasons, belonging to 8 phyla, 39 classes, 87 orders, 100 families, and 265 genera. The Phaeophyceae phylum exhibited the highest abundance in species composition throughout all seasons. Overall, Shannon diversity, Simpson diversity, and Pielou"s evenness index exhibited a pattern of spring > summer > autumn, with highly significant seasonal differences (P < 0.001). Eukaryotic phytoplankton communities showed highly significant seasonal differences (P < 0.001). Summer eukaryotic phytoplankton community assembly was dominated by stochastic processes, while spring and autumn communities were dominated by deterministic processes. All three seasons exhibited highly significant geographic decay trends (P < 0.001), elevation decay trends (P < 0.001), and environmental decay trends (P < 0.001). Interactions among eukaryotic phytoplankton communities were predominantly cooperative. Environmental factors significantly explained more community variation than geographic and altitude factors across all seasons. Key environmental drivers for spring eukaryotic phytoplankton communities were pH, dissolved oxygen (DO), water temperature (WT), turbidity (TUR), ammonium nitrogen (NH??-N), and altitude (ALT); summer: electrical conductivity (EC) and water temperature (WT); autumn: water temperature (WT), dissolved oxygen (DO), and electrical conductivity (EC). Water temperature exerted a highly significant influence on eukaryotic phytoplankton communities across all three seasons. This study employed high-throughput amplicon sequencing to analyze the spatiotemporal structure of eukaryotic phytoplankton communities in the river basin. It revealed the distribution patterns and variation characteristics of eukaryotic phytoplankton communities in plateau rivers, providing crucial evidence for microbial diversity conservation and aquatic ecosystem health management in plateau regions.
The Yarlung Tsangpo River is one of the world"s major international rivers and also one of the most sensitive and fragile ecosystems globally. Eukaryotic phytoplankton play a vital role in maintaining the ecological balance of this river ecosystem. To reveal the diversity, spatiotemporal distribution characteristics, and key driving factors of eukaryotic phytoplankton communities in the Nyang River and Palong Tsangpo, representative primary tributaries of the lower Yarlung Tsangpo River, this study employed high-throughput amplicon sequencing technology to investigate the diversity patterns and driving factors of eukaryotic phytoplankton across three seasons spring, summer, and autumn—in this watershed. Results revealed that 6,723 ASVs of eukaryotic phytoplankton were identified across the three seasons, belonging to 8 phyla, 39 classes, 87 orders, 100 families, and 265 genera. The Phaeophyceae phylum exhibited the highest abundance in species composition throughout all seasons. Overall, Shannon diversity, Simpson diversity, and Pielou"s evenness index exhibited a pattern of spring > summer > autumn, with highly significant seasonal differences (P < 0.001). Eukaryotic phytoplankton communities showed highly significant seasonal differences (P < 0.001). Summer eukaryotic phytoplankton community assembly was dominated by stochastic processes, while spring and autumn communities were dominated by deterministic processes. All three seasons exhibited highly significant geographic decay trends (P < 0.001), elevation decay trends (P < 0.001), and environmental decay trends (P < 0.001). Interactions among eukaryotic phytoplankton communities were predominantly cooperative. Environmental factors significantly explained more community variation than geographic and altitude factors across all seasons. Key environmental drivers for spring eukaryotic phytoplankton communities were pH, dissolved oxygen (DO), water temperature (WT), turbidity (TUR), ammonium nitrogen (NH??-N), and altitude (ALT); summer: electrical conductivity (EC) and water temperature (WT); autumn: water temperature (WT), dissolved oxygen (DO), and electrical conductivity (EC). Water temperature exerted a highly significant influence on eukaryotic phytoplankton communities across all three seasons. This study employed high-throughput amplicon sequencing to analyze the spatiotemporal structure of eukaryotic phytoplankton communities in the river basin. It revealed the distribution patterns and variation characteristics of eukaryotic phytoplankton communities in plateau rivers, providing crucial evidence for microbial diversity conservation and aquatic ecosystem health management in plateau regions.
Available online: March 19, 2026
Abstract:
Suspended particulate matter (SPM) is a key optically active constituent in lake water. Its concentration governs turbidity, water colour and transparency, and therefore serves as a critical indicator of lake water quality. Taihu, Hongze and Chao—the three largest lakes in the middle–lower Yangtze River basin—exhibit pronounced spatio-temporal SPM variabilitydriven by both natural processes and human activities. Although polar-orbiting satellites have been widely used to characterize seasonal-to-interannual SPM dynamics, the scarcity of cloud-free images severely limits analyses at monthly or daily resolution.Here, 132 620 Level-2 images from the Geostationary Ocean Color Imager (GOCI) acquired between April 2011 and December 2020, together with quasi-synchronous in-situ data collected over the three lakes, were used to evaluate existing SPM algorithms. After selection and optimisation, the best-performing algorithm was applied to the quality-controlled GOCI imagery to generate a long-term hourly SPM concentration dataset.The dataset is provided in GeoTIFF format under the geographic coordinate system GCS_WGS_1984 and consists of 13 262 files. On average, the number of valid observational days per month (defined as the fraction of usable pixels > 85 %) is 9.1 for Taihu, 7.6 for Hongze and 7.5 for Chao. Cross-validation shows excellent agreement between satellite retrievals and field measurements in both spatial patterns and long-term temporal trends (R2 > 0.90, MAPE < 15 %, RMSE < 5 mg L?1), demonstrating the robustness and reliability of the product.Compared with polar-orbiting satellite products, the present dataset offers an order-of-magnitude improvement in temporal resolution, delivering complete SPM dynamics at daily and monthly scales and accurately capturing seasonal and inter-annual variations. The dense time series further enables high-frequency SPM monitoring, allowing short-term, high-magnitude disturbances—such as rainstorm runoff, dredging and water-diversion events—to be resolved. The dataset thus provides essential support for elucidating the short- and long-term mechanisms underlying SPM spatio-temporal variability and is of great value for lake management and scientific research.
Suspended particulate matter (SPM) is a key optically active constituent in lake water. Its concentration governs turbidity, water colour and transparency, and therefore serves as a critical indicator of lake water quality. Taihu, Hongze and Chao—the three largest lakes in the middle–lower Yangtze River basin—exhibit pronounced spatio-temporal SPM variabilitydriven by both natural processes and human activities. Although polar-orbiting satellites have been widely used to characterize seasonal-to-interannual SPM dynamics, the scarcity of cloud-free images severely limits analyses at monthly or daily resolution.Here, 132 620 Level-2 images from the Geostationary Ocean Color Imager (GOCI) acquired between April 2011 and December 2020, together with quasi-synchronous in-situ data collected over the three lakes, were used to evaluate existing SPM algorithms. After selection and optimisation, the best-performing algorithm was applied to the quality-controlled GOCI imagery to generate a long-term hourly SPM concentration dataset.The dataset is provided in GeoTIFF format under the geographic coordinate system GCS_WGS_1984 and consists of 13 262 files. On average, the number of valid observational days per month (defined as the fraction of usable pixels > 85 %) is 9.1 for Taihu, 7.6 for Hongze and 7.5 for Chao. Cross-validation shows excellent agreement between satellite retrievals and field measurements in both spatial patterns and long-term temporal trends (R2 > 0.90, MAPE < 15 %, RMSE < 5 mg L?1), demonstrating the robustness and reliability of the product.Compared with polar-orbiting satellite products, the present dataset offers an order-of-magnitude improvement in temporal resolution, delivering complete SPM dynamics at daily and monthly scales and accurately capturing seasonal and inter-annual variations. The dense time series further enables high-frequency SPM monitoring, allowing short-term, high-magnitude disturbances—such as rainstorm runoff, dredging and water-diversion events—to be resolved. The dataset thus provides essential support for elucidating the short- and long-term mechanisms underlying SPM spatio-temporal variability and is of great value for lake management and scientific research.
Available online: March 18, 2026
Abstract:
Against the backdrop of intensified global warming and the growing importance of carbon cycle research, inland water bodies in karst regions have emerged as efficient carbon sinks, underscoring the necessity for their accurate identification and comprehensive characterization. Guangxi, a representative karst region in China, lacks a systematic classification of its karst and non-karst lakes and reservoirs (collectively referred to as lacustrine systems), posing a critical gap in both regional and national-scale research. This study aims to address this gap by providing foundational data for future studies of karst lacustrine systems and informing evidence-based strategies for aquatic ecological conservation and management. A total of 788 lakes and reservoirs in Guangxi (each with a surface area exceeding 10 ha) were analyzed using multi-source geospatial datasets including Lake-Topo Cat, World Karst Aquifer Map (WOKAM), and the Global Lithological Map (GLiM). Through GIS-based delineation, morphological features (area, storage capacity, shoreline length) and catchment characteristics were extracted. Lacustrine systems were classified into four categories based on the proportion of karst lithologies within their catchment areas: karst (>75%), semi-karst (35–75%), weakly karstic (10–35%), and non-karst (<10%). A random forest model was subsequently applied to quantify the influence of various environmental variables—climatic (annual precipitation), geological (lithology), topographic, and anthropogenic (population density)—on the spatial distribution of karst lakes and reservoirs. The research shows: (1) Karst lakes and reservoirs are abundant, comprising 314 of the total (40%) and predominantly situated in peak cluster depressions and dissolution basins within central, north-western, south-western, and north-eastern Guangxi.; (2) Karst lacustrine systems exhibit the largest individual surface area (98.25 km2), maximum storage capacity (10,260 mcm), and the most complex shoreline morphology (up to 554.97 km), yet their average area (1.07 km2) and median storage (1.30 mcm) suggest a predominance of small to medium-sized water bodies with a few large outliers; (3) Karst catchments are overwhelmingly dominated by carbonate sedimentary rocks (>90%), in contrast to non-karst systems, which are primarily underlain by siliceous clastic lithologies; (4) Variable importance analysis from the random forest model reveals that carbonate rocks (37.0%), siliceous clastic rocks (28.87%), and annual precipitation (28.0%) are the most critical determinants of karst lake and reservoir distribution. This study presents the first comprehensive cartographic inventory and morphometric characterization of karst lakes and reservoirs in Guangxi. The results highlight lithology—particularly carbonate dominance—and climate, especially precipitation, as primary controls on karst lacustrine formation. The findings not only fill a longstanding data gap in regional hydro-karst research but also provide a scientific basis for watershed management and aquatic ecosystem conservation in karst terrains.
Against the backdrop of intensified global warming and the growing importance of carbon cycle research, inland water bodies in karst regions have emerged as efficient carbon sinks, underscoring the necessity for their accurate identification and comprehensive characterization. Guangxi, a representative karst region in China, lacks a systematic classification of its karst and non-karst lakes and reservoirs (collectively referred to as lacustrine systems), posing a critical gap in both regional and national-scale research. This study aims to address this gap by providing foundational data for future studies of karst lacustrine systems and informing evidence-based strategies for aquatic ecological conservation and management. A total of 788 lakes and reservoirs in Guangxi (each with a surface area exceeding 10 ha) were analyzed using multi-source geospatial datasets including Lake-Topo Cat, World Karst Aquifer Map (WOKAM), and the Global Lithological Map (GLiM). Through GIS-based delineation, morphological features (area, storage capacity, shoreline length) and catchment characteristics were extracted. Lacustrine systems were classified into four categories based on the proportion of karst lithologies within their catchment areas: karst (>75%), semi-karst (35–75%), weakly karstic (10–35%), and non-karst (<10%). A random forest model was subsequently applied to quantify the influence of various environmental variables—climatic (annual precipitation), geological (lithology), topographic, and anthropogenic (population density)—on the spatial distribution of karst lakes and reservoirs. The research shows: (1) Karst lakes and reservoirs are abundant, comprising 314 of the total (40%) and predominantly situated in peak cluster depressions and dissolution basins within central, north-western, south-western, and north-eastern Guangxi.; (2) Karst lacustrine systems exhibit the largest individual surface area (98.25 km2), maximum storage capacity (10,260 mcm), and the most complex shoreline morphology (up to 554.97 km), yet their average area (1.07 km2) and median storage (1.30 mcm) suggest a predominance of small to medium-sized water bodies with a few large outliers; (3) Karst catchments are overwhelmingly dominated by carbonate sedimentary rocks (>90%), in contrast to non-karst systems, which are primarily underlain by siliceous clastic lithologies; (4) Variable importance analysis from the random forest model reveals that carbonate rocks (37.0%), siliceous clastic rocks (28.87%), and annual precipitation (28.0%) are the most critical determinants of karst lake and reservoir distribution. This study presents the first comprehensive cartographic inventory and morphometric characterization of karst lakes and reservoirs in Guangxi. The results highlight lithology—particularly carbonate dominance—and climate, especially precipitation, as primary controls on karst lacustrine formation. The findings not only fill a longstanding data gap in regional hydro-karst research but also provide a scientific basis for watershed management and aquatic ecosystem conservation in karst terrains.
Available online: March 18, 2026
Abstract:
Plateau lakes, owing to their distinctive seasonal ice cover, play a special role in global greenhouse gas (GHG) emissions, characterized by under-ice accumulation in winter and pulsed release during ice-off. Focusing on Lake Wuliangsuhai in Inner Mongolia, this study resolves the spatiotemporal dynamics of CH? and N?O in the overlying water during the freeze-thaw period and their correlations with environmental factors. Based on freeze-thaw-induced biogeochemical processes in sediments, we further examine variations in carbon and nitrogen nutrients in the overlying water and in sedimentary electron acceptors, thereby elucidating the mechanisms governing GHG storage and release during freeze-thaw. Results demonstrate that formation of an ice cover drives cumulative increases in dissolved CH? in the overlying water. The highest surface-water CH? concentration occurred in vegetated zones during the stable frozen stage (93,382.76 nmol/L), whereas the peak N?O concentration was recorded in occurred in non-vegetated zones at the end of thawing (181.93 nmol/L). In contrast to N2O, whose behavior is largely controlled by internal sedimentary processes and mass-transfer limitations, CH4 responds more sensitively to variations in DO and ORP of the overlying water. Across the freeze-thaw cycle, total organic carbon (TOC) and total nitrogen (TN) accumulated during freezing but declined during thawing due to decomposition. Inorganic nitrogen species (NH??-N, NO??-N, NO??-N) shifted dynamically and reciprocally, consistent with active nitrification and denitrification. Carbon and nitrogen migration was jointly regulated by sediment biogeochemistry and redox conditions imposed by freeze-thaw. Sedimentary organic-matter degradation to displayed vertical stratification: nitrate/iron reduction dominated in upper-middle layers, while sulfate reduction prevailed at depth. Methanogenesis accompanied these pathways, with CH? migrating upward across the sediment-water interface and ultimately accumulating beneath the ice.
Plateau lakes, owing to their distinctive seasonal ice cover, play a special role in global greenhouse gas (GHG) emissions, characterized by under-ice accumulation in winter and pulsed release during ice-off. Focusing on Lake Wuliangsuhai in Inner Mongolia, this study resolves the spatiotemporal dynamics of CH? and N?O in the overlying water during the freeze-thaw period and their correlations with environmental factors. Based on freeze-thaw-induced biogeochemical processes in sediments, we further examine variations in carbon and nitrogen nutrients in the overlying water and in sedimentary electron acceptors, thereby elucidating the mechanisms governing GHG storage and release during freeze-thaw. Results demonstrate that formation of an ice cover drives cumulative increases in dissolved CH? in the overlying water. The highest surface-water CH? concentration occurred in vegetated zones during the stable frozen stage (93,382.76 nmol/L), whereas the peak N?O concentration was recorded in occurred in non-vegetated zones at the end of thawing (181.93 nmol/L). In contrast to N2O, whose behavior is largely controlled by internal sedimentary processes and mass-transfer limitations, CH4 responds more sensitively to variations in DO and ORP of the overlying water. Across the freeze-thaw cycle, total organic carbon (TOC) and total nitrogen (TN) accumulated during freezing but declined during thawing due to decomposition. Inorganic nitrogen species (NH??-N, NO??-N, NO??-N) shifted dynamically and reciprocally, consistent with active nitrification and denitrification. Carbon and nitrogen migration was jointly regulated by sediment biogeochemistry and redox conditions imposed by freeze-thaw. Sedimentary organic-matter degradation to displayed vertical stratification: nitrate/iron reduction dominated in upper-middle layers, while sulfate reduction prevailed at depth. Methanogenesis accompanied these pathways, with CH? migrating upward across the sediment-water interface and ultimately accumulating beneath the ice.
Available online: March 16, 2026
Abstract:
The enduring development of limnology and lake science has profoundly demonstrated the importance and necessity of sustained field observation and experimental research. Globally, scientific institutions have established long-term positioning observation field stations, systematically conducting research spanning decades to centuries on the evolutionary mechanisms and sustainable management of lake ecosystems. Notable examples include Flathead Lake, Trout Lake, and Lake Michigan in the United States; Lake Zurich in Switzerland; and Lake Biwa and Lake Kasumigaura in Japan. With the support of the Chinese Ecosystem Research Network and the National Science and Technology Infrastructure Center, Chinese scientists have successively established field observation and experimental stations in Donghu Lake (Wuhan), Taihu Lake, Poyang Lake, Dongting Lake, and Liangzi Lake, conducting long-term experimental observations and comprehensive networked research on lake ecosystems. This article systematically reviews the progress of long-term positioning observation and experimental research in lake science globally and in China. Through cross-country, cross-regional, and cross-lake-type case comparisons, it highlights the irreplaceable role of long-term positioning observation in revealing the dynamic changes of lake ecosystems. The study emphasizes that only through cross-regional networked observations, enhanced informatization and intelligence in monitoring, and the integration of observation with simulation models can we deeply analyze the response thresholds and resilience mechanisms of lake ecosystems to climate warming and human activities. This will provide critical scientific support for the protection, ecological restoration, and sustainable use of lakes worldwide, promoting the leapfrog development of lake science from "phenomenon description" to "mechanism analysis" and "predictive early warning." Ultimately, this serves the United Nations Sustainable Development Agenda and contributes to the building of a Beautiful China.
The enduring development of limnology and lake science has profoundly demonstrated the importance and necessity of sustained field observation and experimental research. Globally, scientific institutions have established long-term positioning observation field stations, systematically conducting research spanning decades to centuries on the evolutionary mechanisms and sustainable management of lake ecosystems. Notable examples include Flathead Lake, Trout Lake, and Lake Michigan in the United States; Lake Zurich in Switzerland; and Lake Biwa and Lake Kasumigaura in Japan. With the support of the Chinese Ecosystem Research Network and the National Science and Technology Infrastructure Center, Chinese scientists have successively established field observation and experimental stations in Donghu Lake (Wuhan), Taihu Lake, Poyang Lake, Dongting Lake, and Liangzi Lake, conducting long-term experimental observations and comprehensive networked research on lake ecosystems. This article systematically reviews the progress of long-term positioning observation and experimental research in lake science globally and in China. Through cross-country, cross-regional, and cross-lake-type case comparisons, it highlights the irreplaceable role of long-term positioning observation in revealing the dynamic changes of lake ecosystems. The study emphasizes that only through cross-regional networked observations, enhanced informatization and intelligence in monitoring, and the integration of observation with simulation models can we deeply analyze the response thresholds and resilience mechanisms of lake ecosystems to climate warming and human activities. This will provide critical scientific support for the protection, ecological restoration, and sustainable use of lakes worldwide, promoting the leapfrog development of lake science from "phenomenon description" to "mechanism analysis" and "predictive early warning." Ultimately, this serves the United Nations Sustainable Development Agenda and contributes to the building of a Beautiful China.
王敬富, Yang Haiquan, Zeng Yan, Yin chao, Chen quan, Ma Yiming, Fang Jinlong, Zhang Yuting, Li Qiuhua, Li Yulin, Chen Jingan
Available online: March 16, 2026
Abstract:
After 15 years of development, the Guizhou Provincial Field Scientific Observation and Research Station for the Hongfeng Reservoir Ecosystem has been established as a comprehensive field observation and research platform integrating observation, research, demonstration, and service for high-altitude deep lake ecosystems. Based on long-term positioning monitoring of typical high-altitude deep lakes and reservoirs, the platform focuses on key scientific issues such as water resource development, water security, and water ecological restoration in the southwestern region. It has conducted in-depth analysis of the basic characteristics of high-altitude deep lake ecosystems, revealed the evolution characteristics and climate responses of these ecosystems, as well as the processes and mechanisms of biogenic element geochemical cycles. A series of key technologies for the protection and restoration of deep lakes and reservoirs have been developed, providing scientific and technological support for regional sustainable development.
After 15 years of development, the Guizhou Provincial Field Scientific Observation and Research Station for the Hongfeng Reservoir Ecosystem has been established as a comprehensive field observation and research platform integrating observation, research, demonstration, and service for high-altitude deep lake ecosystems. Based on long-term positioning monitoring of typical high-altitude deep lakes and reservoirs, the platform focuses on key scientific issues such as water resource development, water security, and water ecological restoration in the southwestern region. It has conducted in-depth analysis of the basic characteristics of high-altitude deep lake ecosystems, revealed the evolution characteristics and climate responses of these ecosystems, as well as the processes and mechanisms of biogenic element geochemical cycles. A series of key technologies for the protection and restoration of deep lakes and reservoirs have been developed, providing scientific and technological support for regional sustainable development.
Available online: March 16, 2026
Abstract:
The Yangtze River, known as the Mother River of the Chinese nation, is a vital cradle of Chinese civilization and a core lifeline supporting China"s economic and social development. The high-quality development of the Yangtze River Economic Belt fundamentally depends on the excellent ecological environment of the Yangtze River Basin. Long-term fixed-site observation of the aquatic ecosystem in the Yangtze River Basin serves as the essential foundation for coordinating the protection and restoration of water resources, water environment, and aquatic ecology in the region. It also holds significant scientific importance for advancing the science of watershed aquatic ecosystems and supporting the implementation of the national strategy for Yangtze River conservation. This paper systematically reviews the progress and experiences in long-term fixed-site observation and experimental research on aquatic ecosystems in major river basins both domestically and internationally. It traces the development history and key achievements of long-term observation and experimental studies on the aquatic ecosystem in the Yangtze River Basin. Furthermore, it summarizes the progress and outcomes achieved since the launch of the Joint Observation Research Initiative for Aquatic Ecosystem Security in the Yangtze River Basin (2023–2025), supported by national field stations, particularly in terms of compiling fundamental datasets on the water ecological environment and developing specialized technical standards for aquatic ecological observation. Addressing the challenges and issues faced by future long-term observation research on the Yangtze River Basin"s aquatic ecosystem, this paper proposes development trends and highlights priority areas that require strengthening in future long-term fixed-site observation and experimental studies. The findings of this paper offer important guidance and practical value for ensuring the aquatic ecological security of the Yangtze River Basin and advancing the national strategy for its conservation.
The Yangtze River, known as the Mother River of the Chinese nation, is a vital cradle of Chinese civilization and a core lifeline supporting China"s economic and social development. The high-quality development of the Yangtze River Economic Belt fundamentally depends on the excellent ecological environment of the Yangtze River Basin. Long-term fixed-site observation of the aquatic ecosystem in the Yangtze River Basin serves as the essential foundation for coordinating the protection and restoration of water resources, water environment, and aquatic ecology in the region. It also holds significant scientific importance for advancing the science of watershed aquatic ecosystems and supporting the implementation of the national strategy for Yangtze River conservation. This paper systematically reviews the progress and experiences in long-term fixed-site observation and experimental research on aquatic ecosystems in major river basins both domestically and internationally. It traces the development history and key achievements of long-term observation and experimental studies on the aquatic ecosystem in the Yangtze River Basin. Furthermore, it summarizes the progress and outcomes achieved since the launch of the Joint Observation Research Initiative for Aquatic Ecosystem Security in the Yangtze River Basin (2023–2025), supported by national field stations, particularly in terms of compiling fundamental datasets on the water ecological environment and developing specialized technical standards for aquatic ecological observation. Addressing the challenges and issues faced by future long-term observation research on the Yangtze River Basin"s aquatic ecosystem, this paper proposes development trends and highlights priority areas that require strengthening in future long-term fixed-site observation and experimental studies. The findings of this paper offer important guidance and practical value for ensuring the aquatic ecological security of the Yangtze River Basin and advancing the national strategy for its conservation.
Available online: March 04, 2026
Abstract:
[Background]Plain reservoirs in arid regions face severe ineffective evaporation loss. Selecting efficient, environmentally friendly, and economically viable physical covering structures to reduce water surface evaporation is a key approach to achieving the sustainable utilization of water resources. [Methods]This study was conducted in Kunyu City, Hotan Prefecture, Xinjiang. A control experiment was established in large evaporation tanks with a diameter of 6 meters. Three types of physical covering materials—homogeneous floating balls, bottom-weighted floating balls, and hexagonal diamond-shaped floating bodies—were used to fully cover the water surface, with an uncovered blank group set as the control. Through long-term continuous monitoring, the evaporation inhibition efficiency of different covering structures under complex meteorological conditions and their impacts on the water environment were systematically evaluated. [Results]The findings revealed that: (1) The water surface evaporation process exhibited significant seasonal fluctuations, and the evaporation inhibition effect of the covering layer was comprehensively driven by meteorological factors; (2) The structural morphology of the covering units had a significant impact on water-saving efficiency. The hexagonal diamond-shaped floating bodies achieved an average evaporation inhibition rate of 75.2% at a coverage rate of 83%; while for the two types of floating balls with a coverage rate of 86%, the bottom-weighted floating balls (70.2%) outperformed the homogeneous floating balls (66.7%); (3) Water quality tests indicated that floating ball coverage did not cause secondary pollution to the water body, and the water quality indicators met the standards for agricultural irrigation. The long-term ecological effects of the hexagonal floating bodies require further quantification;(4) On the premise that the evaporation inhibition efficiency meets the engineering design indicators, the homogeneous floating ball water surface coverage scheme exhibits better economic feasibility and cost-effectiveness.[Conclusions]Different physical covering forms vary in water-saving benefits. In engineering practice, a multi-dimensional trade-off should be made based on water-saving rate, economy, and ecological security. The results of this study can provide theoretical basis and data support for the optimization of evaporation inhibition technologies and efficient water resource management in plain reservoirs of arid regions.
[Background]Plain reservoirs in arid regions face severe ineffective evaporation loss. Selecting efficient, environmentally friendly, and economically viable physical covering structures to reduce water surface evaporation is a key approach to achieving the sustainable utilization of water resources. [Methods]This study was conducted in Kunyu City, Hotan Prefecture, Xinjiang. A control experiment was established in large evaporation tanks with a diameter of 6 meters. Three types of physical covering materials—homogeneous floating balls, bottom-weighted floating balls, and hexagonal diamond-shaped floating bodies—were used to fully cover the water surface, with an uncovered blank group set as the control. Through long-term continuous monitoring, the evaporation inhibition efficiency of different covering structures under complex meteorological conditions and their impacts on the water environment were systematically evaluated. [Results]The findings revealed that: (1) The water surface evaporation process exhibited significant seasonal fluctuations, and the evaporation inhibition effect of the covering layer was comprehensively driven by meteorological factors; (2) The structural morphology of the covering units had a significant impact on water-saving efficiency. The hexagonal diamond-shaped floating bodies achieved an average evaporation inhibition rate of 75.2% at a coverage rate of 83%; while for the two types of floating balls with a coverage rate of 86%, the bottom-weighted floating balls (70.2%) outperformed the homogeneous floating balls (66.7%); (3) Water quality tests indicated that floating ball coverage did not cause secondary pollution to the water body, and the water quality indicators met the standards for agricultural irrigation. The long-term ecological effects of the hexagonal floating bodies require further quantification;(4) On the premise that the evaporation inhibition efficiency meets the engineering design indicators, the homogeneous floating ball water surface coverage scheme exhibits better economic feasibility and cost-effectiveness.[Conclusions]Different physical covering forms vary in water-saving benefits. In engineering practice, a multi-dimensional trade-off should be made based on water-saving rate, economy, and ecological security. The results of this study can provide theoretical basis and data support for the optimization of evaporation inhibition technologies and efficient water resource management in plain reservoirs of arid regions.
Available online: February 04, 2026
Abstract:
Abstract: To explore the impacts of flooding duration on the functional diversity of plants in the drawdown zone of large reservoirs, this study selected three large reservoirs in the southwestern region as the research areas. Through systematic measurement of the functional traits and functional diversity indicators of plants in the floodplain under different flooding durations. The results showed that: 1）A total of 34 species of vascular plants were recorded, belonging to 30 genera and 17 families, and a total of eight dominant species with a coverage ≥ 25% were recorded. 2）The moderately flooded area (MF) exhibits the highest functional diversity, which was significantly higher than those of the slightly flooded area (SF) and the severely flooded area (LF). The trait differentiation and ecological niche differentiation of the dominant species are significant. 3）The functional homogeneity in the LF zone was significantly reduced, and the diversity indices of each function decreased significantly. Only the main root diameter significantly increased (63% higher than the MF zone, and 154% higher than the SF zone), indicating that under strong waterlogging stress, the community constructed a redundant functional structure by specifically thickening the main roots. Cynodon dactylon was a highly specialized key species in these zones. 4）The community coverage, stem branch number, root length and total root fresh weight in the SF area were significantly higher than those in the MF and LF areas. This indicates that mild flooding mainly selects for trait combinations with rapid colonization ability. In this area, the traits of Cynodon dactylon, Eleusine indica, Ageratum conyzoides and Xanthium sibiricum are spatially dispersed and independent. 5）The CV value of leaf traits remains relatively large across the waterlogging gradient, confirming their sensitivity. Overall, in the southwestern reservoir drawdown zone, the duration of flooding is the key driving factor regulating the degree of functional trait dispersion and functional diversity. For the LF area with an average annual flooding duration of ≥ 180 days, a strategy of functional redundancy is adopted; for the area with an average annual flooding duration of < 180 days, a strategy of functional complementarity is adopted. This difference in functional diversity response based on the flooding gradient drives the formation of the multi-adaptive strategies of dominant species. It is suggested to implement differentiated community construction strategies based on the duration of flooding.
Abstract: To explore the impacts of flooding duration on the functional diversity of plants in the drawdown zone of large reservoirs, this study selected three large reservoirs in the southwestern region as the research areas. Through systematic measurement of the functional traits and functional diversity indicators of plants in the floodplain under different flooding durations. The results showed that: 1）A total of 34 species of vascular plants were recorded, belonging to 30 genera and 17 families, and a total of eight dominant species with a coverage ≥ 25% were recorded. 2）The moderately flooded area (MF) exhibits the highest functional diversity, which was significantly higher than those of the slightly flooded area (SF) and the severely flooded area (LF). The trait differentiation and ecological niche differentiation of the dominant species are significant. 3）The functional homogeneity in the LF zone was significantly reduced, and the diversity indices of each function decreased significantly. Only the main root diameter significantly increased (63% higher than the MF zone, and 154% higher than the SF zone), indicating that under strong waterlogging stress, the community constructed a redundant functional structure by specifically thickening the main roots. Cynodon dactylon was a highly specialized key species in these zones. 4）The community coverage, stem branch number, root length and total root fresh weight in the SF area were significantly higher than those in the MF and LF areas. This indicates that mild flooding mainly selects for trait combinations with rapid colonization ability. In this area, the traits of Cynodon dactylon, Eleusine indica, Ageratum conyzoides and Xanthium sibiricum are spatially dispersed and independent. 5）The CV value of leaf traits remains relatively large across the waterlogging gradient, confirming their sensitivity. Overall, in the southwestern reservoir drawdown zone, the duration of flooding is the key driving factor regulating the degree of functional trait dispersion and functional diversity. For the LF area with an average annual flooding duration of ≥ 180 days, a strategy of functional redundancy is adopted; for the area with an average annual flooding duration of < 180 days, a strategy of functional complementarity is adopted. This difference in functional diversity response based on the flooding gradient drives the formation of the multi-adaptive strategies of dominant species. It is suggested to implement differentiated community construction strategies based on the duration of flooding.
Available online: February 04, 2026
Abstract:
Through complex dynamic water exchanges, Poyang Lake and the Yangtze River constitute the Yangtze–Poyang Lake Flood and Low Flow Regulation System, which plays a crucial role in flood and drought prevention in the middle and lower Yangtze region. Utilizing long-term hydrological data and remote sensing interpretations, we clarified the water regulation and storage processes of Poyang Lake in response to inflows from the Yangtze River mainstream and the Five Rivers. By incorporating the operational phases of the Three Gorges Reservoir (TGR), we identified changes in the lake’s flood and low-flow regulation capacity, along with the influencing factors, before and after the TGR’s operation. The main findings are:(1) During the dry season (December to April of the following year) and discharge season (May to early June), the daily regulation volume of Poyang Lake is mostly positive, increasing stored water; during the flood season (mid-June to early September) and impoundment season (mid-September to November), the opposite occurs, while annual total water inflow and outflow remain largely balanced. The daily regulation volume is significantly positively correlated with Yangtze mainstream flow and incoming water from the Five Rivers; (2) After the Three Gorges Reservoir operation, the daily regulation volume changed: positive values increased in the discharge season, the shift from positive to negative occurred earlier in the flood season, and negative values intensified late in the flood season. Consequently, the lake’s water storage decreased by approximately 1.41 billion m3 during the pre-flood season (mid-June) and by roughly 8.55 billion m3 at the end of the flood season (late June), respectively. These changes resulted from Poyang Lake’s enhanced discharge capacity, increased mainstream and tributary flow during the discharge season, and faster recession during the impoundment season; (3) Affected by hydrological processes and storage-discharge adjustments, Poyang Lake’s water storage function weakened in the late flood and discharge seasons. Notable “drawdown” and “rapid flood-drought transition” phenomena led to frequent extreme low water levels and prolonged droughts. Conversely, lower water storage increased Poyang Lake’s available capacity during discharge season, enhancing its regulation of floods from the Five Rivers. By contrast, the Poyang Lake’s smaller pre-flood storage capacity weakened its regulatory effects on Yangtze River floods, making it inadequate for extreme events. Additionally, the lake’s capacity to supplement the Yangtze’s flow declined at the end of the flood season and impoundment season, but remained stable during the dry season. These findings enhance our understanding of Poyang Lake’s regulatory mechanisms and support effective management of the river-lake system.
Through complex dynamic water exchanges, Poyang Lake and the Yangtze River constitute the Yangtze–Poyang Lake Flood and Low Flow Regulation System, which plays a crucial role in flood and drought prevention in the middle and lower Yangtze region. Utilizing long-term hydrological data and remote sensing interpretations, we clarified the water regulation and storage processes of Poyang Lake in response to inflows from the Yangtze River mainstream and the Five Rivers. By incorporating the operational phases of the Three Gorges Reservoir (TGR), we identified changes in the lake’s flood and low-flow regulation capacity, along with the influencing factors, before and after the TGR’s operation. The main findings are:(1) During the dry season (December to April of the following year) and discharge season (May to early June), the daily regulation volume of Poyang Lake is mostly positive, increasing stored water; during the flood season (mid-June to early September) and impoundment season (mid-September to November), the opposite occurs, while annual total water inflow and outflow remain largely balanced. The daily regulation volume is significantly positively correlated with Yangtze mainstream flow and incoming water from the Five Rivers; (2) After the Three Gorges Reservoir operation, the daily regulation volume changed: positive values increased in the discharge season, the shift from positive to negative occurred earlier in the flood season, and negative values intensified late in the flood season. Consequently, the lake’s water storage decreased by approximately 1.41 billion m3 during the pre-flood season (mid-June) and by roughly 8.55 billion m3 at the end of the flood season (late June), respectively. These changes resulted from Poyang Lake’s enhanced discharge capacity, increased mainstream and tributary flow during the discharge season, and faster recession during the impoundment season; (3) Affected by hydrological processes and storage-discharge adjustments, Poyang Lake’s water storage function weakened in the late flood and discharge seasons. Notable “drawdown” and “rapid flood-drought transition” phenomena led to frequent extreme low water levels and prolonged droughts. Conversely, lower water storage increased Poyang Lake’s available capacity during discharge season, enhancing its regulation of floods from the Five Rivers. By contrast, the Poyang Lake’s smaller pre-flood storage capacity weakened its regulatory effects on Yangtze River floods, making it inadequate for extreme events. Additionally, the lake’s capacity to supplement the Yangtze’s flow declined at the end of the flood season and impoundment season, but remained stable during the dry season. These findings enhance our understanding of Poyang Lake’s regulatory mechanisms and support effective management of the river-lake system.
Li Jiang, Duan Zhongzhao, Gao Wei, He Jinliang, Wang Yong, Xing Haojie, Wei Guanghui, Li Zhuoya, He Liancheng, Hou Xikang
Available online: February 04, 2026
Abstract:
As the largest inland drainage lake in China, Lake Bosten plays a critical role in water resource allocation and ecological barrier functions in arid regions. However, the continuous exceedance of the chemical oxygen demand (COD) concentration standard in the lake in recent years has become a prominent issue in regional ecological and environmental governance. This study using the three-dimensional hydrodynamic and water quality model Environmental Fluid Dynamic Code (EFDC) for Lake Bosten. Combined with scenario simulation methods, we systematically reconstructed the dynamics of hydrodynamic conditions and COD concentrations in Lake Bosten from 2014 to 2023. Multiple hydrological regulation scenarios were constructed to evaluate the improvement effects of different measures on the lake’s hydrodynamic conditions and COD concentrations. The results show: 1) Changes in COD concentration in Lake Bosten result from the combined effects of natural processes (high evaporation, low flow velocity, long water residence time) and human activities (reed cultivation areas); 2) The lake exhibits weak hydrodynamic conditions with a west-high-east-low pattern, and effectively enhancing lake-wide hydrodynamic conditions is key to improving COD concentration; 3) The “Kaidu-to-Huangshui Water Diversion” scenario can significantly improve lake hydrodynamics by reallocating inflow, and can reduce COD concentration by 18.37%, making it the optimal regulation scheme. This research can provide a scientific basis for COD control in Lake Bosten and offer insights into pollution management and water quality governance in arid-region lakes.
As the largest inland drainage lake in China, Lake Bosten plays a critical role in water resource allocation and ecological barrier functions in arid regions. However, the continuous exceedance of the chemical oxygen demand (COD) concentration standard in the lake in recent years has become a prominent issue in regional ecological and environmental governance. This study using the three-dimensional hydrodynamic and water quality model Environmental Fluid Dynamic Code (EFDC) for Lake Bosten. Combined with scenario simulation methods, we systematically reconstructed the dynamics of hydrodynamic conditions and COD concentrations in Lake Bosten from 2014 to 2023. Multiple hydrological regulation scenarios were constructed to evaluate the improvement effects of different measures on the lake’s hydrodynamic conditions and COD concentrations. The results show: 1) Changes in COD concentration in Lake Bosten result from the combined effects of natural processes (high evaporation, low flow velocity, long water residence time) and human activities (reed cultivation areas); 2) The lake exhibits weak hydrodynamic conditions with a west-high-east-low pattern, and effectively enhancing lake-wide hydrodynamic conditions is key to improving COD concentration; 3) The “Kaidu-to-Huangshui Water Diversion” scenario can significantly improve lake hydrodynamics by reallocating inflow, and can reduce COD concentration by 18.37%, making it the optimal regulation scheme. This research can provide a scientific basis for COD control in Lake Bosten and offer insights into pollution management and water quality governance in arid-region lakes.
Available online: February 03, 2026
Abstract:
As a critical zone for water quality security in the Danjiangkou Reservoir, its bays have become a focal point for water quality management in the reservoir area. Using long-term monitoring data from 2015 to 2024, this study systematically analyzed the spatiotemporal distribution characteristics of water quality indicators and the comprehensive trophic level index TLI(∑) in the reservoir bays, and explored the correlations between trophic status and algae density，as well as their relationships with water environmental factors. Results indicate that over the past decade, changes in the concentrations of major water quality indicators in the bays of Danjiangkou Reservoir exhibited distinct characteristics. The average concentrations of total nitrogen(TN)and total phosphorus(TP) ranged from 1.08 to 2.34 mg/L and 0.019 to 0.132 mg/L, respectively, while the mean TLI(∑) values varied between 31.05 and 51.26, indicating a generally mesotrophic state in the reservoir bays. Trend analysis revealed a significant decreasing trend in TP concentration and TLI(∑). A mutation point in TLI(∑) was identified between May and October 2018, which is associated with the long-term implementation of water quality management measures in the reservoir area and upstream regions, as well as the regulatory effect of high water level conditions on reservoir bay water quality. Seasonally, water quality indicator concentrations were generally lowest in winter. During the autumn flood season in some years, extreme rainfall events occurred frequently, leading to a sharp rise in reservoir waler level, which significantly increased TN and CODMn concentrations but decreased TP concentration in the bays. Spatially, water quality was relatively poor in the tail areas of Danjiangkou Reservoir，with a high risk of eutrophication in local bays. Correlation analysis and variance decomposition results demonstrated that TLI(∑) was closely associated with pollution input processes, while algal growth was more significantly influenced by physicochemical indicators of the water body, particularly water temperature. These findings provide a scientific basis and decision-making reference for eutrophication and algal bloom prevention and control in the Danjiangkou Reservoir bays.
As a critical zone for water quality security in the Danjiangkou Reservoir, its bays have become a focal point for water quality management in the reservoir area. Using long-term monitoring data from 2015 to 2024, this study systematically analyzed the spatiotemporal distribution characteristics of water quality indicators and the comprehensive trophic level index TLI(∑) in the reservoir bays, and explored the correlations between trophic status and algae density，as well as their relationships with water environmental factors. Results indicate that over the past decade, changes in the concentrations of major water quality indicators in the bays of Danjiangkou Reservoir exhibited distinct characteristics. The average concentrations of total nitrogen(TN)and total phosphorus(TP) ranged from 1.08 to 2.34 mg/L and 0.019 to 0.132 mg/L, respectively, while the mean TLI(∑) values varied between 31.05 and 51.26, indicating a generally mesotrophic state in the reservoir bays. Trend analysis revealed a significant decreasing trend in TP concentration and TLI(∑). A mutation point in TLI(∑) was identified between May and October 2018, which is associated with the long-term implementation of water quality management measures in the reservoir area and upstream regions, as well as the regulatory effect of high water level conditions on reservoir bay water quality. Seasonally, water quality indicator concentrations were generally lowest in winter. During the autumn flood season in some years, extreme rainfall events occurred frequently, leading to a sharp rise in reservoir waler level, which significantly increased TN and CODMn concentrations but decreased TP concentration in the bays. Spatially, water quality was relatively poor in the tail areas of Danjiangkou Reservoir，with a high risk of eutrophication in local bays. Correlation analysis and variance decomposition results demonstrated that TLI(∑) was closely associated with pollution input processes, while algal growth was more significantly influenced by physicochemical indicators of the water body, particularly water temperature. These findings provide a scientific basis and decision-making reference for eutrophication and algal bloom prevention and control in the Danjiangkou Reservoir bays.
Available online: February 03, 2026
Abstract:
The coupling coordination between water sensitivity and industrial water environmental pollution stress in lake basins represents an important pathway for achieving sustainable watershed development. This study established an evaluation index system for both water sensitivity and industrial water environmental pollution stress at the small-watershed scale. By applying the coupling coordination degree model, spatial Markov chain, and grey relational analysis, the spatiotemporal evolution characteristics and driving factors of their coupling coordination in the Taihu Basin from 2007 to 2020 were examined. The results revealed that: (1) From 2007 to 2020, water sensitivity in the Taihu Basin declined slightly, generally exhibiting a spatial pattern of “high in the southwest and low in the east”. In contrast, industrial water environmental pollution stress increased significantly, with an S-shaped high-stress belt forming in the east and low stress persisting in the west, indicating notable spatial differentiation. (2) The overall coupling coordination degree between water sensitivity and industrial water environmental pollution stress declined, displaying a “higher in the west and lower in the east” spatial distribution pattern, alongside characteristics of “club convergence” and a certain degree of spatial spillover effect. (3) The coupling coordination degree in the Taihu Basin was influenced by relevant factors, including regional technological investment level, industrial structure, population agglomeration degree, strength of environmental regulation, and socio-economic development level, with significant spatial differences in the effects of these factors. Thus, this study proposes implementing differentiated water environmental regulation policies, optimizing the spatial layout of productivity within the basin, and improving comprehensive watershed management, ecological compensation, and monitoring and early warning systems to foster sustainable development of lake basins.
The coupling coordination between water sensitivity and industrial water environmental pollution stress in lake basins represents an important pathway for achieving sustainable watershed development. This study established an evaluation index system for both water sensitivity and industrial water environmental pollution stress at the small-watershed scale. By applying the coupling coordination degree model, spatial Markov chain, and grey relational analysis, the spatiotemporal evolution characteristics and driving factors of their coupling coordination in the Taihu Basin from 2007 to 2020 were examined. The results revealed that: (1) From 2007 to 2020, water sensitivity in the Taihu Basin declined slightly, generally exhibiting a spatial pattern of “high in the southwest and low in the east”. In contrast, industrial water environmental pollution stress increased significantly, with an S-shaped high-stress belt forming in the east and low stress persisting in the west, indicating notable spatial differentiation. (2) The overall coupling coordination degree between water sensitivity and industrial water environmental pollution stress declined, displaying a “higher in the west and lower in the east” spatial distribution pattern, alongside characteristics of “club convergence” and a certain degree of spatial spillover effect. (3) The coupling coordination degree in the Taihu Basin was influenced by relevant factors, including regional technological investment level, industrial structure, population agglomeration degree, strength of environmental regulation, and socio-economic development level, with significant spatial differences in the effects of these factors. Thus, this study proposes implementing differentiated water environmental regulation policies, optimizing the spatial layout of productivity within the basin, and improving comprehensive watershed management, ecological compensation, and monitoring and early warning systems to foster sustainable development of lake basins.
liu bao gui, qian jie qiong, xu jie, li ning yu, wang ying, zeng lin qin, xu nuo, zhong li lin, xu xiao guang, jin wen jie
Available online: February 03, 2026
Abstract:
Stream ecosystems possess significant ecological value due to their rich aquatic biodiversity and unique characteristics, yet they are highly vulnerable and require urgent attention and protection. Zooplankton, as an important component of the aquatic food web, is often overlooked in terms of its functional role in stream ecosystems. To better understand the ecological function of zooplankton in these environments, this study focused on the headwaters of the Chishui River, a minimally disturbed basin, and compared the taxonomic and functional group characteristics of zooplankton under two distinct hydrological conditions: the dry season (December) and the wet season (May). Relationships between these characteristics and water environmental factors were also analyzed. A total of 29 zooplankton species were identified, with species richness in the dry season (24 species) being twice that in the wet season (12 species). Compared to other aquatic systems, stream zooplankton density was extremely low, ranging from 0.02 to 4.9 ind./L. Based on functional traits such as habitat preference, body size, and feeding habit, taxonomic groups were classified into 11 functional groups. Dominant functional groups included the occasional planktonic benthic scraper, the small to medium-sized swimming predator, and the small filter-feeder, all reflecting adaptive strategies to turbulent lotic habitats. Notably, the proportion of the benthic scraper group increased sharply from 17.7% in the dry season to 68.4% in the wet season, demonstrating high sensitivity to hydrological shifts. Mantel tests further revealed that functional group composition was significantly correlated with multiple environmental factors, including phytoplankton cell density, water temperature, pH, oxidation-reduction potential, total phosphorus, and ammonium nitrogen, indicating that functional groups serve as more sensitive environmental indicators than taxonomic groups. This study demonstrates that functional group classification can integrate species with similar ecological niches, effectively compensating for the limitations of taxonomic approaches in assessing stream zooplankton standing stock, thereby offering a new theoretical perspective for constructing diagnostic indicator systems for stream ecological health.
Stream ecosystems possess significant ecological value due to their rich aquatic biodiversity and unique characteristics, yet they are highly vulnerable and require urgent attention and protection. Zooplankton, as an important component of the aquatic food web, is often overlooked in terms of its functional role in stream ecosystems. To better understand the ecological function of zooplankton in these environments, this study focused on the headwaters of the Chishui River, a minimally disturbed basin, and compared the taxonomic and functional group characteristics of zooplankton under two distinct hydrological conditions: the dry season (December) and the wet season (May). Relationships between these characteristics and water environmental factors were also analyzed. A total of 29 zooplankton species were identified, with species richness in the dry season (24 species) being twice that in the wet season (12 species). Compared to other aquatic systems, stream zooplankton density was extremely low, ranging from 0.02 to 4.9 ind./L. Based on functional traits such as habitat preference, body size, and feeding habit, taxonomic groups were classified into 11 functional groups. Dominant functional groups included the occasional planktonic benthic scraper, the small to medium-sized swimming predator, and the small filter-feeder, all reflecting adaptive strategies to turbulent lotic habitats. Notably, the proportion of the benthic scraper group increased sharply from 17.7% in the dry season to 68.4% in the wet season, demonstrating high sensitivity to hydrological shifts. Mantel tests further revealed that functional group composition was significantly correlated with multiple environmental factors, including phytoplankton cell density, water temperature, pH, oxidation-reduction potential, total phosphorus, and ammonium nitrogen, indicating that functional groups serve as more sensitive environmental indicators than taxonomic groups. This study demonstrates that functional group classification can integrate species with similar ecological niches, effectively compensating for the limitations of taxonomic approaches in assessing stream zooplankton standing stock, thereby offering a new theoretical perspective for constructing diagnostic indicator systems for stream ecological health.
XIE Lingli, JIANG Min, WANG Sheng, WEN Lujie, YIN Denghua, LIU Xiangrong, LIU Tengteng, JIANG Chao, LIU Kai
Available online: February 02, 2026
Abstract:
Freshwater mussels play a vital role in maintaining aquatic ecosystem stability and are effective bioindicators of environmental change. In the Yangtze River Basin, mussel populations have experienced significant declines due to habitat degradation, hydrological alterations, and human disturbances. Understanding the genetic diversity and population structure of dominant species such as Cristaria plicata is crucial for evaluating their adaptive potential and guiding conservation strategies. In this study, mitochondrial cox1 and Cytb genes were used to assess the genetic diversity and population structure of C. plicata from four representative river-connected lakes in the middle and lower Yangtze River Basin: Shijiu Lake (SJ), Qili Lake (QL), Poyang Lake (PY), and Dongting Lake (DT). A total of 120 individuals were collected across hydrologically connected sites, and 90 cox1 and 42 Cytb haplotypes were identified. Haplotype diversity (Hd) and nucleotide diversity (π) were high (cox1: Hd = 0.951, π = 0.03310; Cytb: Hd = 0.855, π = 0.02118), with the DT population showing the highest diversity. Pairwise Fst and AMOVA analyses revealed significant genetic differentiation between SJ and the DT and PY populations (P < 0.01), but not between SJ and QL, and most genetic variation occurred within populations (cox1: 78.01%; Cytb: 83.23%). Neutrality and mismatch distribution tests indicated recent population expansion in SJ and QL, while PY and DT populations appeared relatively stable. The haplotype network and phylogenetic tree suggested partial gene exchange among lakes but also revealed region-specific lineages shaped by limited connectivity. Overall, C. plicata populations in the four lakes exhibited a characteristic “high Hd–low π” pattern, implying historical bottlenecks followed by expansion. Interestingly, smaller lakes (SJ and QL) contained more haplotypes than larger lakes (PY and DT). This pattern likely results from stochastic genetic drift, bottleneck recovery, and microhabitat heterogeneity in small, semi-isolated systems, where periodic hydrological isolation and reconnection alter gene frequencies. In contrast, large lakes with greater hydrological connectivity, habitat diversity, and abundant host fish resources maintain higher overall genetic variation through continuous gene flow. The observed spatial differences demonstrate that lake size, water connectivity, and ecological heterogeneity are the principal drivers of genetic diversity and population structure in C. plicata. Anthropogenic disturbances and hydrological fragmentation further exacerbate local genetic differentiation, particularly in smaller lakes.In conclusion, this study provides comprehensive evidence that C. plicata populations in the Yangtze River lake–river system maintain high genetic diversity but exhibit spatially structured genetic patterns shaped by hydrological connectivity and lake characteristics. Preserving ecological connectivity, protecting host fish resources, and reducing habitat fragmentation are essential for maintaining genetic variation and ensuring the long-term stability of freshwater mussel populations in the Yangtze Basin.
Freshwater mussels play a vital role in maintaining aquatic ecosystem stability and are effective bioindicators of environmental change. In the Yangtze River Basin, mussel populations have experienced significant declines due to habitat degradation, hydrological alterations, and human disturbances. Understanding the genetic diversity and population structure of dominant species such as Cristaria plicata is crucial for evaluating their adaptive potential and guiding conservation strategies. In this study, mitochondrial cox1 and Cytb genes were used to assess the genetic diversity and population structure of C. plicata from four representative river-connected lakes in the middle and lower Yangtze River Basin: Shijiu Lake (SJ), Qili Lake (QL), Poyang Lake (PY), and Dongting Lake (DT). A total of 120 individuals were collected across hydrologically connected sites, and 90 cox1 and 42 Cytb haplotypes were identified. Haplotype diversity (Hd) and nucleotide diversity (π) were high (cox1: Hd = 0.951, π = 0.03310; Cytb: Hd = 0.855, π = 0.02118), with the DT population showing the highest diversity. Pairwise Fst and AMOVA analyses revealed significant genetic differentiation between SJ and the DT and PY populations (P < 0.01), but not between SJ and QL, and most genetic variation occurred within populations (cox1: 78.01%; Cytb: 83.23%). Neutrality and mismatch distribution tests indicated recent population expansion in SJ and QL, while PY and DT populations appeared relatively stable. The haplotype network and phylogenetic tree suggested partial gene exchange among lakes but also revealed region-specific lineages shaped by limited connectivity. Overall, C. plicata populations in the four lakes exhibited a characteristic “high Hd–low π” pattern, implying historical bottlenecks followed by expansion. Interestingly, smaller lakes (SJ and QL) contained more haplotypes than larger lakes (PY and DT). This pattern likely results from stochastic genetic drift, bottleneck recovery, and microhabitat heterogeneity in small, semi-isolated systems, where periodic hydrological isolation and reconnection alter gene frequencies. In contrast, large lakes with greater hydrological connectivity, habitat diversity, and abundant host fish resources maintain higher overall genetic variation through continuous gene flow. The observed spatial differences demonstrate that lake size, water connectivity, and ecological heterogeneity are the principal drivers of genetic diversity and population structure in C. plicata. Anthropogenic disturbances and hydrological fragmentation further exacerbate local genetic differentiation, particularly in smaller lakes.In conclusion, this study provides comprehensive evidence that C. plicata populations in the Yangtze River lake–river system maintain high genetic diversity but exhibit spatially structured genetic patterns shaped by hydrological connectivity and lake characteristics. Preserving ecological connectivity, protecting host fish resources, and reducing habitat fragmentation are essential for maintaining genetic variation and ensuring the long-term stability of freshwater mussel populations in the Yangtze Basin.
Available online: February 02, 2026
Abstract:
Abstract: Lake Xiliang, a representative macrophyte-dominated lake in the middle and lower reaches of the Yangtze River, offers critical insights into regional environmental management through the historical record of heavy metal pollution preserved in its sedimentary deposits. By integrating 210Pb and 137Cs dating of a sediment core with comprehensive geochemical analyses (Al, K, Ti, Ca, Mg, Zn, Cr, Cu, As, Cd, and Pb), organic matter content, enrichment factors (EF), and potential ecological risk indices (Er, RI), this study reconstructs the temporal evolution of heavy metal contamination and associated ecological risks in Lake Xiliang from 1858 to 2021. The findings indicate that the history of heavy metal pollution and ecological risk can be divided into three distinct phases. Stage I (1858—1963) represents a period dominated by natural processes, characterized by negligible heavy metal enrichment (EF≈1) and low ecological risk (RI<75). During Stage II (1963~1988), agricultural activities led to increased accumulation of As, Cd, and Pb (EF>1.5); however, the buffering capacity of the macrophyte-dominated ecosystem, evidenced through carbonate precipitation (as reflected by elevated Ca/(Mg+Al) ratios) and dilution effects, effectively mitigated observable ecological risks. In Stage III (1988~2021), industrial discharges significantly intensified contamination, particularly for Cd, Pb, and Zn, with Cd showing the most pronounced enrichment (EF>8). The RI increased to 111, indicating moderate ecological risk, with Cd contributing up to 84%. Positive Matrix Factorization (PMF) analysis revealed that the contribution of natural sources decreased from 54% to 3% since 1858, while contributions from agricultural sources (dominated by As, Zn, and Pb) and industrial sources (dominated by Cd and Zn) increased to 44% and 54%, respectively. The ecological risk index for Cd exceeded the high-risk threshold (>80) in 1993, likely due to the combined effects of industrial pollutant inputs and reduced ecological buffering capacity resulting from vegetation degradation, which promoted remobilization of heavy metal species. This study elucidates a dual mechanism of "pollution buffering–risk transformation" in macrophyte-dominated lakes during heavy metal accumulation and release phases, a process distinct from that in algal-dominated lakes, thereby providing a scientific basis for differentiated management strategies and ecological restoration in diverse lake ecosystems of the middle and lower Yangtze River.
Abstract: Lake Xiliang, a representative macrophyte-dominated lake in the middle and lower reaches of the Yangtze River, offers critical insights into regional environmental management through the historical record of heavy metal pollution preserved in its sedimentary deposits. By integrating 210Pb and 137Cs dating of a sediment core with comprehensive geochemical analyses (Al, K, Ti, Ca, Mg, Zn, Cr, Cu, As, Cd, and Pb), organic matter content, enrichment factors (EF), and potential ecological risk indices (Er, RI), this study reconstructs the temporal evolution of heavy metal contamination and associated ecological risks in Lake Xiliang from 1858 to 2021. The findings indicate that the history of heavy metal pollution and ecological risk can be divided into three distinct phases. Stage I (1858—1963) represents a period dominated by natural processes, characterized by negligible heavy metal enrichment (EF≈1) and low ecological risk (RI<75). During Stage II (1963~1988), agricultural activities led to increased accumulation of As, Cd, and Pb (EF>1.5); however, the buffering capacity of the macrophyte-dominated ecosystem, evidenced through carbonate precipitation (as reflected by elevated Ca/(Mg+Al) ratios) and dilution effects, effectively mitigated observable ecological risks. In Stage III (1988~2021), industrial discharges significantly intensified contamination, particularly for Cd, Pb, and Zn, with Cd showing the most pronounced enrichment (EF>8). The RI increased to 111, indicating moderate ecological risk, with Cd contributing up to 84%. Positive Matrix Factorization (PMF) analysis revealed that the contribution of natural sources decreased from 54% to 3% since 1858, while contributions from agricultural sources (dominated by As, Zn, and Pb) and industrial sources (dominated by Cd and Zn) increased to 44% and 54%, respectively. The ecological risk index for Cd exceeded the high-risk threshold (>80) in 1993, likely due to the combined effects of industrial pollutant inputs and reduced ecological buffering capacity resulting from vegetation degradation, which promoted remobilization of heavy metal species. This study elucidates a dual mechanism of "pollution buffering–risk transformation" in macrophyte-dominated lakes during heavy metal accumulation and release phases, a process distinct from that in algal-dominated lakes, thereby providing a scientific basis for differentiated management strategies and ecological restoration in diverse lake ecosystems of the middle and lower Yangtze River.
Available online: January 30, 2026
Abstract:
affecting the initiation and dissipation of Microcystis blooms. Nutrients represent a key factor driving microbial growth, and fluctuations in nutrient levels frequently accompany Microcystis bloom cycles. To explore how nutrient variations shape the bacterial communities associated with Microcystis colonies, this study employed a non-axenic strain of colonial Microcystis aeruginosa isolated from Lake Taihu as the model system. Through a multi-nutrient gradient culture experiment, the effects of different nutrient regimes—including nitrogen-deficient (ND), oligotrophic (O), mesotrophic (M), eutrophic (E), and highly eutrophic (BG-11) conditions—were evaluated, and the responses of the associated bacterial communities to nutrient fluctuations during Microcystis growth were analyzed. Results demonstrate that nutrient concentration significantly modulates bacterial community composition and alpha-diversity. Communities under ND, O, and M conditions exhibited greater similarity to each other, whereas those under E and BG-11 conditions diverged more markedly. Elevated nitrogen and phosphorus levels were associated with reduced community richness and diversity. Core bacterial phyla included Proteobacteria, Bacteroidota, and Armatimonadota, with dominant orders such as Rhizobiales, Caulobacterales, and Pseudomonadales. Core taxa varied across nutrient regimes: the BG-11 group was characterized by Actinobacteria and Cytophagales; the O group featured Bradyrhizobiaceae and Hyphomicrobiaceae; the ND group was dominated by Rhizobiales; and the M group showed prominence of Comamonadaceae, underscoring nutrient-driven shifts in the Microcystis-associated bacteriome. Furthermore, nutrient gradients influenced community stability and interaction patterns: under eutrophic conditions, Microcystis displayed stronger resistance and responsiveness, while bacterial cooperation prevailed in oligotrophic settings, shifting toward competitive interactions under nutrient enrichment. This study elucidates how nutrient gradients regulate algal–bacterial interactions and associated microbial community assembly, offering mechanistic insights into the persistence of Microcystis blooms across trophic gradients.
affecting the initiation and dissipation of Microcystis blooms. Nutrients represent a key factor driving microbial growth, and fluctuations in nutrient levels frequently accompany Microcystis bloom cycles. To explore how nutrient variations shape the bacterial communities associated with Microcystis colonies, this study employed a non-axenic strain of colonial Microcystis aeruginosa isolated from Lake Taihu as the model system. Through a multi-nutrient gradient culture experiment, the effects of different nutrient regimes—including nitrogen-deficient (ND), oligotrophic (O), mesotrophic (M), eutrophic (E), and highly eutrophic (BG-11) conditions—were evaluated, and the responses of the associated bacterial communities to nutrient fluctuations during Microcystis growth were analyzed. Results demonstrate that nutrient concentration significantly modulates bacterial community composition and alpha-diversity. Communities under ND, O, and M conditions exhibited greater similarity to each other, whereas those under E and BG-11 conditions diverged more markedly. Elevated nitrogen and phosphorus levels were associated with reduced community richness and diversity. Core bacterial phyla included Proteobacteria, Bacteroidota, and Armatimonadota, with dominant orders such as Rhizobiales, Caulobacterales, and Pseudomonadales. Core taxa varied across nutrient regimes: the BG-11 group was characterized by Actinobacteria and Cytophagales; the O group featured Bradyrhizobiaceae and Hyphomicrobiaceae; the ND group was dominated by Rhizobiales; and the M group showed prominence of Comamonadaceae, underscoring nutrient-driven shifts in the Microcystis-associated bacteriome. Furthermore, nutrient gradients influenced community stability and interaction patterns: under eutrophic conditions, Microcystis displayed stronger resistance and responsiveness, while bacterial cooperation prevailed in oligotrophic settings, shifting toward competitive interactions under nutrient enrichment. This study elucidates how nutrient gradients regulate algal–bacterial interactions and associated microbial community assembly, offering mechanistic insights into the persistence of Microcystis blooms across trophic gradients.
Available online: January 28, 2026
Abstract:
Wetlands serve as crucial carbon reservoirs within terrestrial ecosystems, with plant-derived and microbial-derived organic carbon being essential components for the stable accumulation of soil organic carbon (SOC) in these environments. Lake wetlands represent complex ecological systems that integrate hydrological, topographical, and vegetational elements, and are characterized by notable elevation variations due to their position at the interface between water and land. This study examined the surface (0–20 cm) and subsurface (20–40 cm) soil layers of the Poyang Lake wetland. By integrating data on aboveground and belowground plant communities with fundamental soil physicochemical properties, the research aimed to elucidate the distribution patterns and determining factors of plant-derived and microbial-derived organic carbon along elevation gradients. The findings indicated that SOC content in the surface soil was markedly higher than in the subsurface soil at corresponding elevations, and displayed a gradual increasing trend with elevation. In contrast, SOC content in the subsurface soil did not exhibit significant variation along the elevation gradient (P > 0.05). Furthermore, the contributions of microbial-derived organic carbon (ranging from 28.21% to 62.66% in surface soil and from 23.44% to 54.10% in subsurface soil) to total SOC were significantly greater than those of plant-derived organic carbon (ranging from 15.81% to 25.85% in surface soil and from 16.73% to 28.35% in subsurface soil) at all corresponding elevations (P < 0.05). Both the absolute content of microbial-derived organic carbon and its proportional contribution to SOC increased progressively along the elevation gradient in both surface and subsurface soils, whereas plant-derived organic carbon did not show any significant trend in variation. Analysis using a partial least squares path model further revealed that plants and soil properties primarily influenced SOC content in the surface soil through their effects on microbial-derived organic carbon, whereas their impact on SOC in the subsurface soil was relatively minimal.
Wetlands serve as crucial carbon reservoirs within terrestrial ecosystems, with plant-derived and microbial-derived organic carbon being essential components for the stable accumulation of soil organic carbon (SOC) in these environments. Lake wetlands represent complex ecological systems that integrate hydrological, topographical, and vegetational elements, and are characterized by notable elevation variations due to their position at the interface between water and land. This study examined the surface (0–20 cm) and subsurface (20–40 cm) soil layers of the Poyang Lake wetland. By integrating data on aboveground and belowground plant communities with fundamental soil physicochemical properties, the research aimed to elucidate the distribution patterns and determining factors of plant-derived and microbial-derived organic carbon along elevation gradients. The findings indicated that SOC content in the surface soil was markedly higher than in the subsurface soil at corresponding elevations, and displayed a gradual increasing trend with elevation. In contrast, SOC content in the subsurface soil did not exhibit significant variation along the elevation gradient (P > 0.05). Furthermore, the contributions of microbial-derived organic carbon (ranging from 28.21% to 62.66% in surface soil and from 23.44% to 54.10% in subsurface soil) to total SOC were significantly greater than those of plant-derived organic carbon (ranging from 15.81% to 25.85% in surface soil and from 16.73% to 28.35% in subsurface soil) at all corresponding elevations (P < 0.05). Both the absolute content of microbial-derived organic carbon and its proportional contribution to SOC increased progressively along the elevation gradient in both surface and subsurface soils, whereas plant-derived organic carbon did not show any significant trend in variation. Analysis using a partial least squares path model further revealed that plants and soil properties primarily influenced SOC content in the surface soil through their effects on microbial-derived organic carbon, whereas their impact on SOC in the subsurface soil was relatively minimal.
Fu Mei, Wu Tongfei, Lyu Hongjian, Lu Taoxiu, Wu Kaiyang, Zhang Lianbo, Xi Dan, Tian Zhili, Yang Li, Li Xiaoqin, Yao Weizhi
Available online: January 27, 2026
Abstract:
Mortality is one of the crucial factors influencing fish population dynamics. The fish instantaneous mortality rate is a key parameter depicting the process and characteristics of fish death, and it holds significant theoretical and practical importance in fishery stock assessment and management models. However, it was often neglected due to assessment difficulties. To understand the mortality characteristics of plateau Schizothoraciae fish in China and explore suitable methods for assessing their instantaneous mortality rate, this study analyzed the population of Gymnodiptychus pachycheilus (189 individuals) collected from the middle reaches of the Yalong River from 2020 to 2021. The total instantaneous mortality rate (Z) was estimated using the weighted linear regression, Chapman-Robson method, and the Beverton-Holt method. The Natural Mortality Tool (NMT) was used to estimate the instantaneous natural mortality rate (M) and assess the reliability of all these estimates. Additionally, the Maunder model was employed to analyze the impact of sex and age differences on the M of G. pachycheilus. Meanwhile, the NMT was used to estimate M of 26 stock of 18 Schizothoraciae species (including G. pachycheilus). The results indicated that the Z estimated by the Chapman-Robson and weighted linear regression methods (0.88 year-1 and 0.89 year-1, respectively) were more reliable than that estimated by the Beverton-Holt method. Methods based on maximum capture age and growth parameters tend to overestimate and underestimate M of G. pachycheilus respectively. However, the M estimated by the weighted combination using NMT (0.23 year-1) proved more reliable than using traditional single-method, with the corresponding fishing instantaneous mortality rate (F) between 0.65 and 0.66 year-1. This suggests that the G. pachycheilus population in the middle reaches of the Yalong River may be facing significant environmental pressures (including fishing death caused by illegal fishing, and natural death caused by pollution and habitat loss). Furthermore, the Maunder model analysis revealed that G. pachycheilus faces a minor peak of natural death upon entering the reproductive phase, other than the high mortality levels of the juvenile stage. The M of females was higher than that of males only between the ages of 4.71 and 5.31, while it was lower for females at other times. Most Schizothoraciae fish in other studies exhibited a similar pattern where the M of females exceeded that of males. Additionally, the study found that Schizothoraciae fish classified as highly specialized and specialized species (including G. pachycheilus) generally had a higher M compared with those classified as primitive species, and the latter had lower and more dispersed M. Based on these results, it is feasible to develop a general method evaluate the M for Schizothoraciae fish in China, and the M could be a valuable indicator to assess the population dynamics
Mortality is one of the crucial factors influencing fish population dynamics. The fish instantaneous mortality rate is a key parameter depicting the process and characteristics of fish death, and it holds significant theoretical and practical importance in fishery stock assessment and management models. However, it was often neglected due to assessment difficulties. To understand the mortality characteristics of plateau Schizothoraciae fish in China and explore suitable methods for assessing their instantaneous mortality rate, this study analyzed the population of Gymnodiptychus pachycheilus (189 individuals) collected from the middle reaches of the Yalong River from 2020 to 2021. The total instantaneous mortality rate (Z) was estimated using the weighted linear regression, Chapman-Robson method, and the Beverton-Holt method. The Natural Mortality Tool (NMT) was used to estimate the instantaneous natural mortality rate (M) and assess the reliability of all these estimates. Additionally, the Maunder model was employed to analyze the impact of sex and age differences on the M of G. pachycheilus. Meanwhile, the NMT was used to estimate M of 26 stock of 18 Schizothoraciae species (including G. pachycheilus). The results indicated that the Z estimated by the Chapman-Robson and weighted linear regression methods (0.88 year-1 and 0.89 year-1, respectively) were more reliable than that estimated by the Beverton-Holt method. Methods based on maximum capture age and growth parameters tend to overestimate and underestimate M of G. pachycheilus respectively. However, the M estimated by the weighted combination using NMT (0.23 year-1) proved more reliable than using traditional single-method, with the corresponding fishing instantaneous mortality rate (F) between 0.65 and 0.66 year-1. This suggests that the G. pachycheilus population in the middle reaches of the Yalong River may be facing significant environmental pressures (including fishing death caused by illegal fishing, and natural death caused by pollution and habitat loss). Furthermore, the Maunder model analysis revealed that G. pachycheilus faces a minor peak of natural death upon entering the reproductive phase, other than the high mortality levels of the juvenile stage. The M of females was higher than that of males only between the ages of 4.71 and 5.31, while it was lower for females at other times. Most Schizothoraciae fish in other studies exhibited a similar pattern where the M of females exceeded that of males. Additionally, the study found that Schizothoraciae fish classified as highly specialized and specialized species (including G. pachycheilus) generally had a higher M compared with those classified as primitive species, and the latter had lower and more dispersed M. Based on these results, it is feasible to develop a general method evaluate the M for Schizothoraciae fish in China, and the M could be a valuable indicator to assess the population dynamics
Available online: January 26, 2026
Abstract:
To implement the national strategy of "River Basin Ecological Protection" and address the synergistic threats of salinization and groundwater-derived pollution faced by the oasis groundwater systems in the arid regions of northwest China, this study takes the Manas River Basin as the research object and integrates interdisciplinary methods to reveal the synergistic risk-forming mechanisms of salinization and pollution as well as the transmission paths of health risks. Combining field sampling and laboratory analysis, the study employs the Entropy-Weighted Water Quality Index (EWQI) and health risk assessment models to analyze groundwater quality and exposure risks. It identifies natural and anthropogenically driven hydrogeochemical processes through hydrochemical evolution analysis and constructs a “salinity-pollution-risk” ternary coupling model by drawing on ideas of ecological zoning evaluation, realizing quantitative characterization and spatial zoning of multi-factor synergistic risks.The results show that the groundwater in the basin is weakly alkaline, with hydrochemical types evolving from HCO3·SO4-Ca in the south to SO4·Cl-Na in the north. The water quality in the northern oasis-desert transition zone deteriorates significantly, with over-standard rates of As, F-, and NO3- reaching 70.40%, 48.00%, and 31.20% respectively. Among them, the carcinogenic risk (CR) of As to children and adults exceeds the international thresholds by 11.4 times and 5.3 times respectively. The basin transitions from being dominated by rock weathering in the south to evaporation-concentration in the north. Salinization intensifies pollutant enrichment through evaporation-concentration and cation exchange, and combined with agricultural non-point sources and industrial emissions, forms complex pollution. The overall water quality of the basin is good, but the over-standard rate of Class Ⅲ water in the oasis-desert transition zone reaches 27.58%. Water quality deterioration is driven by both agricultural pollution and evaporation-concentration. Cl- is the main contributing factor to non-carcinogenic risks, while priority should be given to preventing and controlling children"s exposure to As-induced carcinogenic risks. TDS shows an extremely significant positive correlation with Cl- and Na+ (r=0.939, 0.840), and As concentration is highly correlated with children"s CR (r=0.825), forming a "salinity-pollution-risk" chain synergistic effect.Based on the ternary coupling model, the basin is divided into high-risk areas (18.40%, urgent treatment), medium-risk areas (27.20%, dynamic monitoring), low-risk areas (21.60%, preventive management), and safe areas (32.80%, long-term protection), with differentiated control strategies proposed. This study reveals the synergistic risk-forming laws of natural geological processes and human activities in arid region groundwater systems, providing a scientific paradigm integrating ecological zoning ideas and quantitative assessment methods for multi-element collaborative management of oasis water resources along the Belt and Road Initiative.
To implement the national strategy of "River Basin Ecological Protection" and address the synergistic threats of salinization and groundwater-derived pollution faced by the oasis groundwater systems in the arid regions of northwest China, this study takes the Manas River Basin as the research object and integrates interdisciplinary methods to reveal the synergistic risk-forming mechanisms of salinization and pollution as well as the transmission paths of health risks. Combining field sampling and laboratory analysis, the study employs the Entropy-Weighted Water Quality Index (EWQI) and health risk assessment models to analyze groundwater quality and exposure risks. It identifies natural and anthropogenically driven hydrogeochemical processes through hydrochemical evolution analysis and constructs a “salinity-pollution-risk” ternary coupling model by drawing on ideas of ecological zoning evaluation, realizing quantitative characterization and spatial zoning of multi-factor synergistic risks.The results show that the groundwater in the basin is weakly alkaline, with hydrochemical types evolving from HCO3·SO4-Ca in the south to SO4·Cl-Na in the north. The water quality in the northern oasis-desert transition zone deteriorates significantly, with over-standard rates of As, F-, and NO3- reaching 70.40%, 48.00%, and 31.20% respectively. Among them, the carcinogenic risk (CR) of As to children and adults exceeds the international thresholds by 11.4 times and 5.3 times respectively. The basin transitions from being dominated by rock weathering in the south to evaporation-concentration in the north. Salinization intensifies pollutant enrichment through evaporation-concentration and cation exchange, and combined with agricultural non-point sources and industrial emissions, forms complex pollution. The overall water quality of the basin is good, but the over-standard rate of Class Ⅲ water in the oasis-desert transition zone reaches 27.58%. Water quality deterioration is driven by both agricultural pollution and evaporation-concentration. Cl- is the main contributing factor to non-carcinogenic risks, while priority should be given to preventing and controlling children"s exposure to As-induced carcinogenic risks. TDS shows an extremely significant positive correlation with Cl- and Na+ (r=0.939, 0.840), and As concentration is highly correlated with children"s CR (r=0.825), forming a "salinity-pollution-risk" chain synergistic effect.Based on the ternary coupling model, the basin is divided into high-risk areas (18.40%, urgent treatment), medium-risk areas (27.20%, dynamic monitoring), low-risk areas (21.60%, preventive management), and safe areas (32.80%, long-term protection), with differentiated control strategies proposed. This study reveals the synergistic risk-forming laws of natural geological processes and human activities in arid region groundwater systems, providing a scientific paradigm integrating ecological zoning ideas and quantitative assessment methods for multi-element collaborative management of oasis water resources along the Belt and Road Initiative.
Available online: January 26, 2026
Abstract:
Phytoplankton, as primary producers in aquatic ecosystems, reflect the ecological structure and functional status of water bodies. As a major tributary of the Yangtze River and the largest river in the Poyang Lake Basin, the Ganjiang River is subject to the combined impacts of complex hydrological conditions and human activities, making phytoplankton highly sensitive to environmental changes. Based on hydroecological survey data of the mainstream of Ganjiang River (Ganzhou to Nanchang) between 2019 and 2024, combined with historical literature from 1980s, this study reveals the spatiotemporal distribution patterns and long-term succession characteristics of phytoplankton communities over nearly 40 years. Results indicate that 6 phyla and 84 species of phytoplankton were identified from 2019 to 2024, with Bacillariophyta being the dominant phylum. Spatially, the average total biomass of GJ11 (the south branch of the Ganjiang River) was the highest, while GJ5, GJ6, and GJ7 (the reservoir-controlled sections in the middle reaches) were lower. Seasonally, the highest biomass occurred in July 2020, and the lowest in January 2022. Redundancy analysis (RDA) revealed that CODMn, total phosphorus, ammonia nitrogen, total nitrogen, water temperature, transparency, and phosphate were the core environmental factors regulating phytoplankton community distribution in the mainstream of Ganjiang River, and the influence of river flow (hydrodynamic gradient) was non-negligible. In terms of long-term succession, the dominant phytoplankton groups in the mainstream of Ganjiang River from the 1980s to 2024 underwent a significant shift from " Bacillariophyta + Chlorophyta → cyanobacteria + Bacillariophyta → Bacillariophyta ", reflecting the response of Ganjiang River ecosystem to human activities (pollution, hydraulic engineering) and environmental governance. This study, through the cross-scale data integration of short-term continuous observations and long-term historical tracing, breaks through the limitations of short-term and localized in the previous studies on phytoplankton in the Ganjiang River. It accurately identifies the core driving factors of the spatiotemporal distribution of phytoplankton communities and reveals for the first time the succession patterns and ecological response mechanisms of dominant taxa over the past 40 years. The research results not only provide data support and a scientific basis for the aquatic ecological restoration and long-term management of the Ganjiang River Basin but also offer a typical case and methodological reference for studies on the long-term responses of riverine ecosystems to multiple disturbances.
Phytoplankton, as primary producers in aquatic ecosystems, reflect the ecological structure and functional status of water bodies. As a major tributary of the Yangtze River and the largest river in the Poyang Lake Basin, the Ganjiang River is subject to the combined impacts of complex hydrological conditions and human activities, making phytoplankton highly sensitive to environmental changes. Based on hydroecological survey data of the mainstream of Ganjiang River (Ganzhou to Nanchang) between 2019 and 2024, combined with historical literature from 1980s, this study reveals the spatiotemporal distribution patterns and long-term succession characteristics of phytoplankton communities over nearly 40 years. Results indicate that 6 phyla and 84 species of phytoplankton were identified from 2019 to 2024, with Bacillariophyta being the dominant phylum. Spatially, the average total biomass of GJ11 (the south branch of the Ganjiang River) was the highest, while GJ5, GJ6, and GJ7 (the reservoir-controlled sections in the middle reaches) were lower. Seasonally, the highest biomass occurred in July 2020, and the lowest in January 2022. Redundancy analysis (RDA) revealed that CODMn, total phosphorus, ammonia nitrogen, total nitrogen, water temperature, transparency, and phosphate were the core environmental factors regulating phytoplankton community distribution in the mainstream of Ganjiang River, and the influence of river flow (hydrodynamic gradient) was non-negligible. In terms of long-term succession, the dominant phytoplankton groups in the mainstream of Ganjiang River from the 1980s to 2024 underwent a significant shift from " Bacillariophyta + Chlorophyta → cyanobacteria + Bacillariophyta → Bacillariophyta ", reflecting the response of Ganjiang River ecosystem to human activities (pollution, hydraulic engineering) and environmental governance. This study, through the cross-scale data integration of short-term continuous observations and long-term historical tracing, breaks through the limitations of short-term and localized in the previous studies on phytoplankton in the Ganjiang River. It accurately identifies the core driving factors of the spatiotemporal distribution of phytoplankton communities and reveals for the first time the succession patterns and ecological response mechanisms of dominant taxa over the past 40 years. The research results not only provide data support and a scientific basis for the aquatic ecological restoration and long-term management of the Ganjiang River Basin but also offer a typical case and methodological reference for studies on the long-term responses of riverine ecosystems to multiple disturbances.
Available online: January 21, 2026
Abstract:
Environmental DNA (eDNA)-based biological monitoring has rapidly advanced in recent years, exhibiting a transformative potential that is increasingly supplementing or replacing conventional field survey approaches. Amid this expanding application, where numerous researchers are adopting eDNA methodologies for studies and publications, several underlying risks may compromise the validity of conclusions and the scientific value of resulting papers. For instance, what biological entity does eDNA monitoring actually reflect？Is it appropriate to interpret eDNA-derived data using traditional ecological concepts and analytical frameworks originally developed for individual-based survey data? To address these concerns, this study examines the applicability of extending quantitative community ecology metrics—commonly used in traditional surveys—to eDNA-based data analysis. We focus on four key questions: (1) What biological or ecological attribute does the relative sequence abundance of each detected species represent in eDNA results？ (2) What do community-level metrics calculated from sequence relative abundances actually indicate？(3) How effective is it to substitute sequence relative abundance for individual counts or biomass when computing community indices？(4) How should a conceptual and terminological framework be constructed for quantifying and describing community metrics derived from eDNA data？Based on this analysis, we propose three recommendations for reporting and interpreting eDNA-based biological monitoring and community analyses: first, eDNA results should be carefully described and not equated directly with outcomes from traditional surveys; second, the ecological meaning of eDNA monitoring outputs must be scientifically clarified to avoid ambiguous or misleading interpretations; third, a consensus should be gradually developed across research fields using eDNA technology to establish consistent concepts and terminology. This manuscript offers a preliminary exploration of fundamental issues in eDNA-based monitoring and analysis, aiming to stimulate further discussion and methodological refinement.
Environmental DNA (eDNA)-based biological monitoring has rapidly advanced in recent years, exhibiting a transformative potential that is increasingly supplementing or replacing conventional field survey approaches. Amid this expanding application, where numerous researchers are adopting eDNA methodologies for studies and publications, several underlying risks may compromise the validity of conclusions and the scientific value of resulting papers. For instance, what biological entity does eDNA monitoring actually reflect？Is it appropriate to interpret eDNA-derived data using traditional ecological concepts and analytical frameworks originally developed for individual-based survey data? To address these concerns, this study examines the applicability of extending quantitative community ecology metrics—commonly used in traditional surveys—to eDNA-based data analysis. We focus on four key questions: (1) What biological or ecological attribute does the relative sequence abundance of each detected species represent in eDNA results？ (2) What do community-level metrics calculated from sequence relative abundances actually indicate？(3) How effective is it to substitute sequence relative abundance for individual counts or biomass when computing community indices？(4) How should a conceptual and terminological framework be constructed for quantifying and describing community metrics derived from eDNA data？Based on this analysis, we propose three recommendations for reporting and interpreting eDNA-based biological monitoring and community analyses: first, eDNA results should be carefully described and not equated directly with outcomes from traditional surveys; second, the ecological meaning of eDNA monitoring outputs must be scientifically clarified to avoid ambiguous or misleading interpretations; third, a consensus should be gradually developed across research fields using eDNA technology to establish consistent concepts and terminology. This manuscript offers a preliminary exploration of fundamental issues in eDNA-based monitoring and analysis, aiming to stimulate further discussion and methodological refinement.
Wangjin, Zhuang xinfeng, Tang caihong, Cai yongjiu, Gong zhijun, Zhang shanghong, Kong xiangzhen, Deng jianming
Available online: January 21, 2026
Abstract:
Lake ecosystem stability is a critical indicator of ecological health. To address limitations in existing assessment methods—including inadequate environmental representativeness and excessive data dependency—this study developed a Lake Ecosystem Stability Index grounded in the ecosystem stability framework proposed by Pararov et al. By incorporating lake-specific ecological characteristics and selecting representative indicators, the index integrates both structural and functional dimensions to quantify and compare stability across shallow lakes. The research integrates monthly phytoplankton and zooplankton biomass data from 2016 to 2021, quarterly data from 2022 to 2023, and meteorological and water quality data from Lake Hongze and Lake Luoma, along with monthly monitoring data from Lake Taihu from 2016 to 2023, to quantitatively assess the structural and functional stability of these lakes. The findings reveal: (1) Since 2020, the comprehensive structural stability index decreased from 0.567 ± 0.02 to 0.437 ± 0.04, while the functional stability index has remained stable, indicating that the functional stability of lake ecosystems generally surpasses structural stability(2) Comparative analysis revealed significantly higher ecosystem stability in Lake Taihu than in Lake Hongze and Lake Luoma.(3) Correlation analysis demonstrates that meteorological, water quality, and hydrological factors exhibit highly consistent associations with the structural and functional stability of Lake Hongze and Lake Luoma, but divergent patterns in Lake Taihu. Notably, nitrogen and phosphorus indicators in water quality exhibit the strongest correlations with the structural and functional stability of all three lakes. The dual-dimensional stability index proposed in this study offers a new perspective and quantitative approach for dynamic monitoring and assessment of lake ecosystem stability. It facilitates the identification of differences between structural and functional dimensions, and provides valuable reference for incorporating stability metrics into future lake health assessments and ecological restoration strategies.
Lake ecosystem stability is a critical indicator of ecological health. To address limitations in existing assessment methods—including inadequate environmental representativeness and excessive data dependency—this study developed a Lake Ecosystem Stability Index grounded in the ecosystem stability framework proposed by Pararov et al. By incorporating lake-specific ecological characteristics and selecting representative indicators, the index integrates both structural and functional dimensions to quantify and compare stability across shallow lakes. The research integrates monthly phytoplankton and zooplankton biomass data from 2016 to 2021, quarterly data from 2022 to 2023, and meteorological and water quality data from Lake Hongze and Lake Luoma, along with monthly monitoring data from Lake Taihu from 2016 to 2023, to quantitatively assess the structural and functional stability of these lakes. The findings reveal: (1) Since 2020, the comprehensive structural stability index decreased from 0.567 ± 0.02 to 0.437 ± 0.04, while the functional stability index has remained stable, indicating that the functional stability of lake ecosystems generally surpasses structural stability(2) Comparative analysis revealed significantly higher ecosystem stability in Lake Taihu than in Lake Hongze and Lake Luoma.(3) Correlation analysis demonstrates that meteorological, water quality, and hydrological factors exhibit highly consistent associations with the structural and functional stability of Lake Hongze and Lake Luoma, but divergent patterns in Lake Taihu. Notably, nitrogen and phosphorus indicators in water quality exhibit the strongest correlations with the structural and functional stability of all three lakes. The dual-dimensional stability index proposed in this study offers a new perspective and quantitative approach for dynamic monitoring and assessment of lake ecosystem stability. It facilitates the identification of differences between structural and functional dimensions, and provides valuable reference for incorporating stability metrics into future lake health assessments and ecological restoration strategies.
Available online: January 20, 2026
Abstract:
Eutrophic lakes are one of the important sources of nitrous oxide (N2O) emission, accurate estimation of their N2O emissions is crucial for evaluating the global N2O budget. However, constrained by the spatiotemporal variability of N2O emissions and the complexity of influencing factors, the specific mechanisms by which eutrophication processes affect N2O emissions remain unclear. Therefore, this study selected Lake Taihu, the third largest freshwater lake in China, as the research area. The N2O diffusive fluxes at the water-air interface were measured using the headspace equilibrium method, and the key factors driving N2O emissions were analyzed. The results showed that: (1) The N2O diffusive fluxes at the water-air interface of Lake Taihu ranged from 1.7 to 30.6 μmol/m2/d, with an annual average of 8.9±5.1 μmol/m2/d. Although the eutrophication level in algal-dominated zones was significantly higher than that in macrophyte-dominated and transitional zones (P<0.05), no significant difference in N2O emissions was detected among the three zones (P>0.05). This finding indicates that for moderately eutrophic lakes like Lake Taihu, increasing the eutrophication does not necessarily lead to elevated in lake N2O emissions. (2) Water temperature was the most important factor affecting N2O emissions from Lake Taihu. Further analysis revealed that N2O emission processes in Lake Taihu were co-regulated by the concentrations of dissolved organic carbon and nitrate in the water column. (3) Based on these findings, this study developed a multiple regression model which can effectively correct the overestimation of N2O emissions from Lake Taihu by the IPCC simply through the inclusion of water temperature, an easily accessible environmental factor. This study broads our understanding of how lake eutrophication processes influence N2O emissions, while also providing scientific support for the estimation of N2O emissions.
Eutrophic lakes are one of the important sources of nitrous oxide (N2O) emission, accurate estimation of their N2O emissions is crucial for evaluating the global N2O budget. However, constrained by the spatiotemporal variability of N2O emissions and the complexity of influencing factors, the specific mechanisms by which eutrophication processes affect N2O emissions remain unclear. Therefore, this study selected Lake Taihu, the third largest freshwater lake in China, as the research area. The N2O diffusive fluxes at the water-air interface were measured using the headspace equilibrium method, and the key factors driving N2O emissions were analyzed. The results showed that: (1) The N2O diffusive fluxes at the water-air interface of Lake Taihu ranged from 1.7 to 30.6 μmol/m2/d, with an annual average of 8.9±5.1 μmol/m2/d. Although the eutrophication level in algal-dominated zones was significantly higher than that in macrophyte-dominated and transitional zones (P<0.05), no significant difference in N2O emissions was detected among the three zones (P>0.05). This finding indicates that for moderately eutrophic lakes like Lake Taihu, increasing the eutrophication does not necessarily lead to elevated in lake N2O emissions. (2) Water temperature was the most important factor affecting N2O emissions from Lake Taihu. Further analysis revealed that N2O emission processes in Lake Taihu were co-regulated by the concentrations of dissolved organic carbon and nitrate in the water column. (3) Based on these findings, this study developed a multiple regression model which can effectively correct the overestimation of N2O emissions from Lake Taihu by the IPCC simply through the inclusion of water temperature, an easily accessible environmental factor. This study broads our understanding of how lake eutrophication processes influence N2O emissions, while also providing scientific support for the estimation of N2O emissions.
Available online: January 19, 2026
Abstract:
The metalimnetic oxygen minimum (MOM) are widely observed in deep lakes and may pose substantial risks to ecosystem stability and key ecological functions. Lake Fuxian, storing nearly 50% of Class I freshwater resources in China, plays a vital role in national water resource security. However, the mechanisms underlying MOM formation in Lake Fuxian and its long-term response to climate warming remain poorly understood. Based on high-frequency monitoring data from 2021 to 2024 and a process-based hydrodynamic-ecological model (GOTM-WET), this study reconstructed the evolution of MOM in Lake Fuxian from 1945 to 2024. Scenario simulations were employed to identify and quantify the major oxygen-consuming processes that drive MOM formation and dynamics. The results showed that MOM had occurred persistently during stratified periods since the 1980s. Relative to 1980, DO concentration within the MOM zone declined at a rate of 0.20 ± 0.03 mg/L/decade, while its occurrence depth shoaled by 0.45 ± 0.21 m/decade and thickness increased by 1.07 ± 0.17 m/decade. The volume proportion of MOM relative to the metalimnion rose by 6.44 ± 0.98 %/decade, and its annual duration extended by 31.20 ± 5.08 days/decade. These long-term trends were significantly correlated with enhanced thermal stratification, including increased Schmidt stability, shallower metalimnion, and longer stratification periods. This suggested that climate warming intensified hypoxia risk by providing more stable and persistent physical conditions for oxygen-consuming biogeochemical processes in the metalimnion. Model results indicated that phytoplankton respiration was the dominant oxygen-consuming pathway in the metalimnion (accounting for 62.7% of total consumption), followed by dissolved organic matter (DOM) mineralization (17.3%), particulate organic matter (POM) mineralization (9.8%), and nitrification (9.3%), with sediment oxygen demand (SOD) contributing the least (0.9%). In the MOM zone, the relative importance of DOM mineralization, POM mineralization, and nitrification increased significantly, contributing 27.5%, 19.7%, and 16.7%, respectively. Scenario analyses further revealed that DOM mineralization and net oxygen consumption by phytoplankton (including both direct metabolism and indirectly induced oxygen-consumption processes) were the primary drivers of MOM formation. Meanwhile, POM mineralization, nitrification, and SOD regulated the intensity, persistence, and vertical distribution of MOM, together forming a critical process network sustaining oxygen depletion in the metalimnion. Overall, this study highlights a coupled physical-biogeochemical mechanism of MOM development in deep lakes under climate warming, whereby enhanced stratification and oxygen-consuming processes jointly drive low-oxygen conditions. These findings provide scientific insights for understanding ecosystem responses in deep lakes to climate change and for formulating effective management strategies.
The metalimnetic oxygen minimum (MOM) are widely observed in deep lakes and may pose substantial risks to ecosystem stability and key ecological functions. Lake Fuxian, storing nearly 50% of Class I freshwater resources in China, plays a vital role in national water resource security. However, the mechanisms underlying MOM formation in Lake Fuxian and its long-term response to climate warming remain poorly understood. Based on high-frequency monitoring data from 2021 to 2024 and a process-based hydrodynamic-ecological model (GOTM-WET), this study reconstructed the evolution of MOM in Lake Fuxian from 1945 to 2024. Scenario simulations were employed to identify and quantify the major oxygen-consuming processes that drive MOM formation and dynamics. The results showed that MOM had occurred persistently during stratified periods since the 1980s. Relative to 1980, DO concentration within the MOM zone declined at a rate of 0.20 ± 0.03 mg/L/decade, while its occurrence depth shoaled by 0.45 ± 0.21 m/decade and thickness increased by 1.07 ± 0.17 m/decade. The volume proportion of MOM relative to the metalimnion rose by 6.44 ± 0.98 %/decade, and its annual duration extended by 31.20 ± 5.08 days/decade. These long-term trends were significantly correlated with enhanced thermal stratification, including increased Schmidt stability, shallower metalimnion, and longer stratification periods. This suggested that climate warming intensified hypoxia risk by providing more stable and persistent physical conditions for oxygen-consuming biogeochemical processes in the metalimnion. Model results indicated that phytoplankton respiration was the dominant oxygen-consuming pathway in the metalimnion (accounting for 62.7% of total consumption), followed by dissolved organic matter (DOM) mineralization (17.3%), particulate organic matter (POM) mineralization (9.8%), and nitrification (9.3%), with sediment oxygen demand (SOD) contributing the least (0.9%). In the MOM zone, the relative importance of DOM mineralization, POM mineralization, and nitrification increased significantly, contributing 27.5%, 19.7%, and 16.7%, respectively. Scenario analyses further revealed that DOM mineralization and net oxygen consumption by phytoplankton (including both direct metabolism and indirectly induced oxygen-consumption processes) were the primary drivers of MOM formation. Meanwhile, POM mineralization, nitrification, and SOD regulated the intensity, persistence, and vertical distribution of MOM, together forming a critical process network sustaining oxygen depletion in the metalimnion. Overall, this study highlights a coupled physical-biogeochemical mechanism of MOM development in deep lakes under climate warming, whereby enhanced stratification and oxygen-consuming processes jointly drive low-oxygen conditions. These findings provide scientific insights for understanding ecosystem responses in deep lakes to climate change and for formulating effective management strategies.
Available online: January 13, 2026
Abstract:
The Yellow River Protection Law explicitly calls for improving the water-sediment regulation system and enhancing sediment transport capacity. The late stage of pre-flood water-sediment regulation is a critical period for large-scale sediment flushing and capacity recovery at the Xiaolangdi Reservoir. Optimizing the scheduling process of the Sanmenxia Reservoir can effectively provide subsequent driving force for the Xiaolangdi Reservoir. Extensive research has been conducted by scholars both domestically and internationally: research on reservoir scheduling has evolved from single-objective scheduling to multi-objective collaborative optimization, while sediment transport calculation research has diversified into various data-driven models. Despite these advances, research specifically focused on the pre-flood water-sediment regulation period remains insufficient. In particular, the scheduling process at the Sanmenxia Reservoir lacks accurate methods for calculating sediment discharge, and there is limited research on simultaneously enhancing subsequent driving force while balancing hydropower generation and sediment transport benefits.This study focuses on the Sanmenxia Reservoir. Based on water and sediment data from the Tongguan and Sanmenxia hydrological stations from 2003 to 2023, an XGBoost algorithm is used to construct a sediment discharge prediction model. Additionally, a multi-objective optimization scheduling model for the Sanmenxia Reservoir is established using the NSGA-II algorithm to solve scheduling schemes under different inflow water and sediment conditions. The corresponding optimal solutions under these conditions are identified using the VIKOR multi-attribute decision-making method. The results show that the sediment discharge prediction model developed in this study achieves high accuracy and can be effectively used for calculating sediment discharge. Furthermore, the multi-objective optimization scheduling model outperforms the actual scheduling process under typical conditions during late June to early July of the pre-flood period. It not only increases the number of days with discharge exceeding 2600 m3/s but also significantly enhances the daily average discharge during the sluicing period, leading to an overall improvement in outflow during the sluicing period. This effectively alleviates the problem of insufficient subsequent driving force at the Xiaolangdi Reservoir caused by limited natural inflows during the pre-flood stage.
The Yellow River Protection Law explicitly calls for improving the water-sediment regulation system and enhancing sediment transport capacity. The late stage of pre-flood water-sediment regulation is a critical period for large-scale sediment flushing and capacity recovery at the Xiaolangdi Reservoir. Optimizing the scheduling process of the Sanmenxia Reservoir can effectively provide subsequent driving force for the Xiaolangdi Reservoir. Extensive research has been conducted by scholars both domestically and internationally: research on reservoir scheduling has evolved from single-objective scheduling to multi-objective collaborative optimization, while sediment transport calculation research has diversified into various data-driven models. Despite these advances, research specifically focused on the pre-flood water-sediment regulation period remains insufficient. In particular, the scheduling process at the Sanmenxia Reservoir lacks accurate methods for calculating sediment discharge, and there is limited research on simultaneously enhancing subsequent driving force while balancing hydropower generation and sediment transport benefits.This study focuses on the Sanmenxia Reservoir. Based on water and sediment data from the Tongguan and Sanmenxia hydrological stations from 2003 to 2023, an XGBoost algorithm is used to construct a sediment discharge prediction model. Additionally, a multi-objective optimization scheduling model for the Sanmenxia Reservoir is established using the NSGA-II algorithm to solve scheduling schemes under different inflow water and sediment conditions. The corresponding optimal solutions under these conditions are identified using the VIKOR multi-attribute decision-making method. The results show that the sediment discharge prediction model developed in this study achieves high accuracy and can be effectively used for calculating sediment discharge. Furthermore, the multi-objective optimization scheduling model outperforms the actual scheduling process under typical conditions during late June to early July of the pre-flood period. It not only increases the number of days with discharge exceeding 2600 m3/s but also significantly enhances the daily average discharge during the sluicing period, leading to an overall improvement in outflow during the sluicing period. This effectively alleviates the problem of insufficient subsequent driving force at the Xiaolangdi Reservoir caused by limited natural inflows during the pre-flood stage.
Available online: January 13, 2026
Abstract:
Lithium, boron, potassium, and other strategic critical minerals hold irreplaceable positions in the global energy transition and high-tech fields. However, the mechanisms of multi-element co-enrichment in deep-sea salt lakes and the driving factors of their dynamic changes still lack systematic research. The Longmu Co salt lake in Tibet, as a typical high-altitude deep-sea salt lake, provides an ideal carrier for revealing the above mechanisms with its brine characteristics enriched in lithium (Li), boron (B), potassium (K), rubidium (Rb), and cesium (Cs). This study, through 2×2 Km grid sampling and the establishment of a hydro-climate model, analyzes the spatial distribution, vertical differentiation, and driving factors of the dynamic changes of LiCl, B2O3, KCl in the surface brine of Longmu Co salt lake in 2024, as well as the dynamic changes of LiCl, B2O3, KCl from 2009 to 2024. The results show that in 2024, the average concentrations of LiCl, B2O3, and KCl in the brine of Longmu Co salt lake were 609.57 mg/L, 441.44 mg/L, and 5.12 g/L, respectively. The vertical differentiation was significant, with the deep layer (>30 m) having a 9.39% higher LiCl content than the surface layer (0–10 m). Rb2O and Cs2O were enriched synchronously, with the main influencing factors being the blocking effect of the thermocline and the anoxic environment. On the plane, the eastern part of the salt lake formed high-value areas of LiCl and KCl due to evaporation concentration, while the northwestern part had lower concentrations due to the dilution effect of spring water (with an average annual flow rate of 3.41 m3/s). The differentiation of Rb2O and Cs2O was dominated by the adsorption of clay minerals and hydrothermal input. The distribution of resource elements in Longmu Co salt lake is driven by the triple coupling of "high-altitude extreme climate - tectonic plate - hydrothermal activity." The vertical differentiation is influenced by physical barriers, while the planar differentiation is controlled by hydrological and topographical differences. From 2009 to 2024, the content of LiCl decreased by 22.35%, KCl decreased by 24.81%, and B2O3 decreased by 28.83%. The main influencing factors were glacier melting, spring input, and precipitation recharge. The multi-element co-enrichment mechanism of Longmu Co salt lake provides a scientific basis for the efficient development of salt lake resources in Tibet and has important strategic significance for alleviating China"s dependence on imported lithium resources.
Lithium, boron, potassium, and other strategic critical minerals hold irreplaceable positions in the global energy transition and high-tech fields. However, the mechanisms of multi-element co-enrichment in deep-sea salt lakes and the driving factors of their dynamic changes still lack systematic research. The Longmu Co salt lake in Tibet, as a typical high-altitude deep-sea salt lake, provides an ideal carrier for revealing the above mechanisms with its brine characteristics enriched in lithium (Li), boron (B), potassium (K), rubidium (Rb), and cesium (Cs). This study, through 2×2 Km grid sampling and the establishment of a hydro-climate model, analyzes the spatial distribution, vertical differentiation, and driving factors of the dynamic changes of LiCl, B2O3, KCl in the surface brine of Longmu Co salt lake in 2024, as well as the dynamic changes of LiCl, B2O3, KCl from 2009 to 2024. The results show that in 2024, the average concentrations of LiCl, B2O3, and KCl in the brine of Longmu Co salt lake were 609.57 mg/L, 441.44 mg/L, and 5.12 g/L, respectively. The vertical differentiation was significant, with the deep layer (>30 m) having a 9.39% higher LiCl content than the surface layer (0–10 m). Rb2O and Cs2O were enriched synchronously, with the main influencing factors being the blocking effect of the thermocline and the anoxic environment. On the plane, the eastern part of the salt lake formed high-value areas of LiCl and KCl due to evaporation concentration, while the northwestern part had lower concentrations due to the dilution effect of spring water (with an average annual flow rate of 3.41 m3/s). The differentiation of Rb2O and Cs2O was dominated by the adsorption of clay minerals and hydrothermal input. The distribution of resource elements in Longmu Co salt lake is driven by the triple coupling of "high-altitude extreme climate - tectonic plate - hydrothermal activity." The vertical differentiation is influenced by physical barriers, while the planar differentiation is controlled by hydrological and topographical differences. From 2009 to 2024, the content of LiCl decreased by 22.35%, KCl decreased by 24.81%, and B2O3 decreased by 28.83%. The main influencing factors were glacier melting, spring input, and precipitation recharge. The multi-element co-enrichment mechanism of Longmu Co salt lake provides a scientific basis for the efficient development of salt lake resources in Tibet and has important strategic significance for alleviating China"s dependence on imported lithium resources.
Available online: January 09, 2026
Abstract:
The Nenjiang River Basin, as a crucial distribution area for prehistoric cultural sites in Northeast China, is characterized by its abundant water and fishery resources, making it an ideal region for studying the interaction between prehistoric human activities and hydrological conditions. This study, taking Lake Yuejiapao in the Nenjiang River Basin as an example, quantitatively reconstructs the evolution of hydrological conditions and the changes in fishery resources since the Holocene. By integrating regional prehistoric archaeological records, it deeply explores the impact mechanisms of natural resources on prehistoric human survival strategies and settlement evolution. This paper aims to investigate how prehistoric societies, primarily based on a fishing and hunting economy, responded to hydrological fluctuations by adjusting their human-land relationships. The research results indicate: (1) During the period of 13~7 cal kyr BP (Early to Mid-Neolithic), hydrological conditions and fishery resources continuously increased, with the maximum fish productivity reaching 1928.55 t/year, capable of supporting a population capacity of up to 9180 people, sufficient to meet the protein demands for human survival at that time. Ample and stable water and fishery resources promoted settlement development and the formation of a sedentary mode during this period; (2) Around 5.5 cal kyr BP (Late Neolithic), possibly affected by unstable climate fluctuations and floods, the settlements in this region experienced an overall decline. However, the per capita resources might have relatively increased at this time, leading to relatively comfortable individual living conditions and fuller utilization of fishery resources; (3) After approximately 5.0 cal kyr BP, water resources decreased, and fish productivity dropped to 1198.53 t/year. The minimum population capacity supported by these resources reduced to 5705 people. By the Mid-Bronze Age, the fishery resources in Lake Yuejiapao could no longer fully meet the huge demands brought by the rapidly growing population. To address this, people gradually increased livestock rearing to obtain more stable protein, in order to maintain social development; (4) Hydrological changes also promoted the evolution of settlement spatial patterns. Neolithic settlements were located closer to water bodies, while later settlements migrated to higher grounds, reflecting an active avoidance of flood disasters. This paper, for the first time, quantitatively reconstructs hydrological conditions and changes in fishery resources, revealing the close relationship between hydrological conditions and human survival, settlement location, and subsistence patterns. It provides a new perspective for further research on the interaction between humans and the natural environment.
The Nenjiang River Basin, as a crucial distribution area for prehistoric cultural sites in Northeast China, is characterized by its abundant water and fishery resources, making it an ideal region for studying the interaction between prehistoric human activities and hydrological conditions. This study, taking Lake Yuejiapao in the Nenjiang River Basin as an example, quantitatively reconstructs the evolution of hydrological conditions and the changes in fishery resources since the Holocene. By integrating regional prehistoric archaeological records, it deeply explores the impact mechanisms of natural resources on prehistoric human survival strategies and settlement evolution. This paper aims to investigate how prehistoric societies, primarily based on a fishing and hunting economy, responded to hydrological fluctuations by adjusting their human-land relationships. The research results indicate: (1) During the period of 13~7 cal kyr BP (Early to Mid-Neolithic), hydrological conditions and fishery resources continuously increased, with the maximum fish productivity reaching 1928.55 t/year, capable of supporting a population capacity of up to 9180 people, sufficient to meet the protein demands for human survival at that time. Ample and stable water and fishery resources promoted settlement development and the formation of a sedentary mode during this period; (2) Around 5.5 cal kyr BP (Late Neolithic), possibly affected by unstable climate fluctuations and floods, the settlements in this region experienced an overall decline. However, the per capita resources might have relatively increased at this time, leading to relatively comfortable individual living conditions and fuller utilization of fishery resources; (3) After approximately 5.0 cal kyr BP, water resources decreased, and fish productivity dropped to 1198.53 t/year. The minimum population capacity supported by these resources reduced to 5705 people. By the Mid-Bronze Age, the fishery resources in Lake Yuejiapao could no longer fully meet the huge demands brought by the rapidly growing population. To address this, people gradually increased livestock rearing to obtain more stable protein, in order to maintain social development; (4) Hydrological changes also promoted the evolution of settlement spatial patterns. Neolithic settlements were located closer to water bodies, while later settlements migrated to higher grounds, reflecting an active avoidance of flood disasters. This paper, for the first time, quantitatively reconstructs hydrological conditions and changes in fishery resources, revealing the close relationship between hydrological conditions and human survival, settlement location, and subsistence patterns. It provides a new perspective for further research on the interaction between humans and the natural environment.
Available online: January 08, 2026
Abstract:
The interactive stress relationship between ecological security and urbanization level within a watershed essentially reflects the interplay between humans and the environment. Against the backdrop of accelerated urbanization and increasing pressure on the carrying capacity of natural resources and the environment, lake basins are finding it increasingly difficult to provide stable material support and ecological guarantees for regional sustainable development. Within the theoretical framework of the man–land relationship in regional systems, this study conducts a quantitative analysis of ecological security and urbanization levels across various lake basins, and explores the spatial heterogeneity of their interactive stress relationship. The research findings indicate that: 1. Under the joint influence of ecological governance and regional development, the ecological security and urbanization levels of different lake basins have improved to varying degrees, with their spatiotemporal evolution exhibiting significant spatial heterogeneity. 2. Different basins experience varying degrees of stress in the interaction between ecological environment and urbanization, exhibiting distinct patterns of coupling and coordinated evolution. Developed basins tend to demonstrate a higher level of coordination, while regions with a strong ecological foundation often experience lagging urbanization. The differing levels of stress imposed and endured in the interaction between ecological security and urbanization across basins reflect regional disparities shaped by the combined influence of natural conditions and stages of development. 3. There exists a complex interactive stress relationship between ecological security and urbanization, influenced by factors such as natural endowments and stages of development. Developed basins show weakened interactive stress between ecological security and urbanization; in ecologically sound but underdeveloped basins, ecological factors strongly constrain urbanization; in ecologically fragile and underdeveloped basins, a bidirectional stress pattern emerges. Promoting ecological governance and urbanization processes in a manner tailored to local conditions and exploring development pathways with high adaptability and synergy are key to achieving high-quality development in lake basins. The study aims to systematically depict the interactive stress relationship and evolutionary characteristics between ecological security and urbanization level, in order to provide scientific reference and practical examples for sustainable urbanization and ecological civilization construction in lake basins.
The interactive stress relationship between ecological security and urbanization level within a watershed essentially reflects the interplay between humans and the environment. Against the backdrop of accelerated urbanization and increasing pressure on the carrying capacity of natural resources and the environment, lake basins are finding it increasingly difficult to provide stable material support and ecological guarantees for regional sustainable development. Within the theoretical framework of the man–land relationship in regional systems, this study conducts a quantitative analysis of ecological security and urbanization levels across various lake basins, and explores the spatial heterogeneity of their interactive stress relationship. The research findings indicate that: 1. Under the joint influence of ecological governance and regional development, the ecological security and urbanization levels of different lake basins have improved to varying degrees, with their spatiotemporal evolution exhibiting significant spatial heterogeneity. 2. Different basins experience varying degrees of stress in the interaction between ecological environment and urbanization, exhibiting distinct patterns of coupling and coordinated evolution. Developed basins tend to demonstrate a higher level of coordination, while regions with a strong ecological foundation often experience lagging urbanization. The differing levels of stress imposed and endured in the interaction between ecological security and urbanization across basins reflect regional disparities shaped by the combined influence of natural conditions and stages of development. 3. There exists a complex interactive stress relationship between ecological security and urbanization, influenced by factors such as natural endowments and stages of development. Developed basins show weakened interactive stress between ecological security and urbanization; in ecologically sound but underdeveloped basins, ecological factors strongly constrain urbanization; in ecologically fragile and underdeveloped basins, a bidirectional stress pattern emerges. Promoting ecological governance and urbanization processes in a manner tailored to local conditions and exploring development pathways with high adaptability and synergy are key to achieving high-quality development in lake basins. The study aims to systematically depict the interactive stress relationship and evolutionary characteristics between ecological security and urbanization level, in order to provide scientific reference and practical examples for sustainable urbanization and ecological civilization construction in lake basins.
Guo Qingchun, Wu Yaqi, Zhu Bin, Han Qi, Wu Donghao, Shi Yadong, Sun Tiancheng, Zong Yuqing, Xu jin, Lu Zhihua
Available online: January 08, 2026
Abstract:
Metabolites such as 2-methylisoborneol (2-MIB), produced by filamentous cyanobacteria in Taihu Lake, pose a significant threat to the safety of drinking water sources. However, research on the spatiotemporal variation of 2-MIB concentrations in Taihu Lake remains limited. To elucidate the spatiotemporal dynamics and influencing factors of 2-MIB in key source water areas of Taihu Lake, this study focused on Eastern Taihu Lake. Monthly monitoring during the high-temperature period of 2023 and intensive monitoring in critical zones were conducted to analyze the succession of major odor-producing cyanobacteria, the spatiotemporal characteristics of 2-MIB, and its primary driving factors.Monthly investigations revealed that Planktothricoides sp. was the dominant odor-producing cyanobacterium in Eastern Taihu Lake. However, compared to 2022, the peak relative abundance of the mic gene in Planktothricoides sp. decreased from 94.4% in 2022 to 90.8% in 2023. The highest lake-wide 2-MIB concentration (306.3 ng/L) occurred in July. Similarly, the peak concentration (507.8 ng/L) in the Taipu River Estuary - Dongjiaozi area was also observed in July. The highest concentration (352.0 ng/L) in the Taipu River Estuary - Guajingkou area occurred in August.Intensive monitoring in critical zones identified July 13th as the date with the highest recorded 2-MIB concentration (769.6 ng/L).Concentrations in the Taipu River Estuary exhibited dramatic fluctuations, reaching a maximum of 2185.0 ng/L, significantly higher than concentrations observed at Guajingkou or the inflow area from the main body of Taihu Lake.Correlation analysis indicated that water temperature is a prerequisite condition for high 2-MIB events. Total phosphorus (TP) showed a significant positive correlation with 2-MIB concentration, while ammonia nitrogen (NH?-N) exhibited a significant negative correlation. Further analysis of wind speed in the 24 hours preceding high 2-MIB sampling events revealed that wind speeds exceeding 3 m/s caused short-term rapid increases in 2-MIB concentrations in Eastern Taihu Lake, likely due to sediment resuspension. These findings provide a theoretical basis for managing 2-MIB in Eastern Taihu Lake.
Metabolites such as 2-methylisoborneol (2-MIB), produced by filamentous cyanobacteria in Taihu Lake, pose a significant threat to the safety of drinking water sources. However, research on the spatiotemporal variation of 2-MIB concentrations in Taihu Lake remains limited. To elucidate the spatiotemporal dynamics and influencing factors of 2-MIB in key source water areas of Taihu Lake, this study focused on Eastern Taihu Lake. Monthly monitoring during the high-temperature period of 2023 and intensive monitoring in critical zones were conducted to analyze the succession of major odor-producing cyanobacteria, the spatiotemporal characteristics of 2-MIB, and its primary driving factors.Monthly investigations revealed that Planktothricoides sp. was the dominant odor-producing cyanobacterium in Eastern Taihu Lake. However, compared to 2022, the peak relative abundance of the mic gene in Planktothricoides sp. decreased from 94.4% in 2022 to 90.8% in 2023. The highest lake-wide 2-MIB concentration (306.3 ng/L) occurred in July. Similarly, the peak concentration (507.8 ng/L) in the Taipu River Estuary - Dongjiaozi area was also observed in July. The highest concentration (352.0 ng/L) in the Taipu River Estuary - Guajingkou area occurred in August.Intensive monitoring in critical zones identified July 13th as the date with the highest recorded 2-MIB concentration (769.6 ng/L).Concentrations in the Taipu River Estuary exhibited dramatic fluctuations, reaching a maximum of 2185.0 ng/L, significantly higher than concentrations observed at Guajingkou or the inflow area from the main body of Taihu Lake.Correlation analysis indicated that water temperature is a prerequisite condition for high 2-MIB events. Total phosphorus (TP) showed a significant positive correlation with 2-MIB concentration, while ammonia nitrogen (NH?-N) exhibited a significant negative correlation. Further analysis of wind speed in the 24 hours preceding high 2-MIB sampling events revealed that wind speeds exceeding 3 m/s caused short-term rapid increases in 2-MIB concentrations in Eastern Taihu Lake, likely due to sediment resuspension. These findings provide a theoretical basis for managing 2-MIB in Eastern Taihu Lake.
Available online: January 04, 2026
Abstract:
Poyang Lake, the largest freshwater lake in China, plays a critical role in regional water security and the integrity of wetland ecosystems. Seasonal isolated lakes(SILs), as important components of the Poyang Lake wetland system, exhibit dynamic changes in water level and volume that directly affect the lake’s water balance and biodiversity conservation. However, due to limited in situ observations, complex land surface conditions, and frequent wet–dry alternations, existing methods for estimating water volume suffer from limitations in both accuracy and applicability. This study proposes a novel method for estimating the water volume of SILs by integrating multi-source remote sensing data, hydrological connectivity analysis, digital elevation models (DEMs), and limited hydrological measurements. For the first time, high-resolution time series (8-day, 30-meter) data on water surface area, water level, and water volume were reconstructed for 102 SILs from 2000 to 2024. Results show that: (1) the timing of isolated phases varies spatially, with average Xingzi Station water levels of 13.85 m and 14.28 m marking the start and end of isolation in the Ganjiang North tributary; (2) the 102 SILs had an average area of 305.20 km2, accounting for 17.98% of Poyang Lake’s surface water area, with the largest isolated area recorded in 2023 (134.03 km2, 8.29% of the lake’s area that year); (3) during the rising, falling, and dry water stages, the water volume of SILs accounted for 1.91%, 4.13%, and 6% of the total lake volume, respectively. From 2000 to 2024, water volume in northern lakes showed a declining trend, while lakes in the central and southern regions showed increasing trends, playing a positive role in mitigating drought stress in the basin. Overall, this study offers a new technical pathway for hydrological monitoring and management of Poyang Lake and other small, shallow, seasonal lakes, providing a scientific foundation for sustainable water resource use and ecological protection.
Poyang Lake, the largest freshwater lake in China, plays a critical role in regional water security and the integrity of wetland ecosystems. Seasonal isolated lakes(SILs), as important components of the Poyang Lake wetland system, exhibit dynamic changes in water level and volume that directly affect the lake’s water balance and biodiversity conservation. However, due to limited in situ observations, complex land surface conditions, and frequent wet–dry alternations, existing methods for estimating water volume suffer from limitations in both accuracy and applicability. This study proposes a novel method for estimating the water volume of SILs by integrating multi-source remote sensing data, hydrological connectivity analysis, digital elevation models (DEMs), and limited hydrological measurements. For the first time, high-resolution time series (8-day, 30-meter) data on water surface area, water level, and water volume were reconstructed for 102 SILs from 2000 to 2024. Results show that: (1) the timing of isolated phases varies spatially, with average Xingzi Station water levels of 13.85 m and 14.28 m marking the start and end of isolation in the Ganjiang North tributary; (2) the 102 SILs had an average area of 305.20 km2, accounting for 17.98% of Poyang Lake’s surface water area, with the largest isolated area recorded in 2023 (134.03 km2, 8.29% of the lake’s area that year); (3) during the rising, falling, and dry water stages, the water volume of SILs accounted for 1.91%, 4.13%, and 6% of the total lake volume, respectively. From 2000 to 2024, water volume in northern lakes showed a declining trend, while lakes in the central and southern regions showed increasing trends, playing a positive role in mitigating drought stress in the basin. Overall, this study offers a new technical pathway for hydrological monitoring and management of Poyang Lake and other small, shallow, seasonal lakes, providing a scientific foundation for sustainable water resource use and ecological protection.
Available online: January 04, 2026
Abstract:
The transport of sediment particulates and particulate phosphorus (PP) in shallow lakes is critical for sediment accumulation and water quality evolution. To address the unclear mechanisms governing particulate and PP transport in Lake Taihu and their contribution to sediment deposition, this study examined the overall mass balance, transport characteristics, and deposition patterns of suspended solids (SS) and particulate phosphorus entering and leaving the lake. The investigation combined 2024 monitoring of inflow and outflow rivers with a one-month whole-lake sampling campaign in October 2020 that included particle size fractionation, supported by flux balance analysis. Results show that sediment accumulation and associated phosphorus retention in Lake Taihu were pronounced. In 2021, the net SS inflow into the lake was approximately 400000 tons, equivalent to a sediment volume of about 550000 m3 and an annual deposition rate of 0.35 millimeters. During the same period, net PP retention reached 989 tons, with around 73% of the incoming PP entering the lake adsorbed to particulates, indicating that particulate sedimentation serves as the dominant pathway for phosphorus accumulation. Marked differences were observed in particle size distribution and phosphorus speciation between inflow and outflow. Inflowing particulates were dominated by the 20–50 μm fraction, whereas outflowing particulates were primarily in the 0.45–10 μm range. Moreover, the 10–20 μm fraction carried over 80% of the PP. Hydrodynamic processes significantly influenced the spatial distribution of particulates and PP, resulting in a “high in the west and low in the east” pattern for particulates and a “high in the northwest and low in the southeast” distribution for particulate phosphorus.
The transport of sediment particulates and particulate phosphorus (PP) in shallow lakes is critical for sediment accumulation and water quality evolution. To address the unclear mechanisms governing particulate and PP transport in Lake Taihu and their contribution to sediment deposition, this study examined the overall mass balance, transport characteristics, and deposition patterns of suspended solids (SS) and particulate phosphorus entering and leaving the lake. The investigation combined 2024 monitoring of inflow and outflow rivers with a one-month whole-lake sampling campaign in October 2020 that included particle size fractionation, supported by flux balance analysis. Results show that sediment accumulation and associated phosphorus retention in Lake Taihu were pronounced. In 2021, the net SS inflow into the lake was approximately 400000 tons, equivalent to a sediment volume of about 550000 m3 and an annual deposition rate of 0.35 millimeters. During the same period, net PP retention reached 989 tons, with around 73% of the incoming PP entering the lake adsorbed to particulates, indicating that particulate sedimentation serves as the dominant pathway for phosphorus accumulation. Marked differences were observed in particle size distribution and phosphorus speciation between inflow and outflow. Inflowing particulates were dominated by the 20–50 μm fraction, whereas outflowing particulates were primarily in the 0.45–10 μm range. Moreover, the 10–20 μm fraction carried over 80% of the PP. Hydrodynamic processes significantly influenced the spatial distribution of particulates and PP, resulting in a “high in the west and low in the east” pattern for particulates and a “high in the northwest and low in the southeast” distribution for particulate phosphorus.
Xi Ying, Long Jingzhong, Yu Shuilian, Chen Jingyi, Li Kun, Wang Siting, Xu Tao, Huang Yingping, Lv Yuanfei
Available online: December 30, 2025
Abstract:
Periodic water-level fluctuations in the Three Gorges Reservoir have resulted in differential distribution patterns of polycyclic aromatic hydrocarbons (PAHs) in soils across different elevations of the drawdown area. From the perspective of soil colloid–water level coupling, this study compared the colloidal characteristics and PAHs distribution in soils at multiple elevations (155–185 m) in the Xiangxi River bay before and after a complete water-level fluctuation cycle (from June 2022 to June 2023), aiming to reveal the redistribution mechanism of PAHs driven by artificial regulation of water levels. Results indicated that the total PAHs content in soils of the drawdown area decreased by 10.8–59.6% after water-level fluctuation. Soil colloids from different elevations exhibited high stability, which enhanced the transport of the PAH monomer phenanthrene (Phe) in porous media. Among all elevations, soil colloid properties and PAHs distribution at 165 m were the most sensitive to water-level variations. Fluctuations significantly altered soil colloid characteristics at this elevation: after water-level variation, the specific surface area of soil colloids increased by 70.7%, colloid particle size decreased by 13.3%, the absolute value of the Zeta potential increased by 18.8%, and the critical flocculation concentration (CFC) increased fourfold compared to pre-fluctuation values, indicating enhanced colloidal stability and transport capacity. Pearson correlation analysis confirmed that colloid stability and Zeta potential (p < 0.01) were the principal factors controlling PAHs distribution in the drawdown area soils during water-level fluctuations. This suggests that artificial water-level regulation drives the “sink–source” transformation of PAHs in soil by modulating colloid stability and physicochemical properties. These findings provide guidance for understanding the effects of water-level fluctuations on exposed-zone ecosystems and for managing PAH pollution in reservoir waters.
Periodic water-level fluctuations in the Three Gorges Reservoir have resulted in differential distribution patterns of polycyclic aromatic hydrocarbons (PAHs) in soils across different elevations of the drawdown area. From the perspective of soil colloid–water level coupling, this study compared the colloidal characteristics and PAHs distribution in soils at multiple elevations (155–185 m) in the Xiangxi River bay before and after a complete water-level fluctuation cycle (from June 2022 to June 2023), aiming to reveal the redistribution mechanism of PAHs driven by artificial regulation of water levels. Results indicated that the total PAHs content in soils of the drawdown area decreased by 10.8–59.6% after water-level fluctuation. Soil colloids from different elevations exhibited high stability, which enhanced the transport of the PAH monomer phenanthrene (Phe) in porous media. Among all elevations, soil colloid properties and PAHs distribution at 165 m were the most sensitive to water-level variations. Fluctuations significantly altered soil colloid characteristics at this elevation: after water-level variation, the specific surface area of soil colloids increased by 70.7%, colloid particle size decreased by 13.3%, the absolute value of the Zeta potential increased by 18.8%, and the critical flocculation concentration (CFC) increased fourfold compared to pre-fluctuation values, indicating enhanced colloidal stability and transport capacity. Pearson correlation analysis confirmed that colloid stability and Zeta potential (p < 0.01) were the principal factors controlling PAHs distribution in the drawdown area soils during water-level fluctuations. This suggests that artificial water-level regulation drives the “sink–source” transformation of PAHs in soil by modulating colloid stability and physicochemical properties. These findings provide guidance for understanding the effects of water-level fluctuations on exposed-zone ecosystems and for managing PAH pollution in reservoir waters.
Available online: December 23, 2025
Abstract:
Zizania latifolia communities are a key wetland vegetation type in Poyang Lake, and their spatial distribution is significantly affected by the hydrological regimes of the lake. Since the water level of Poyang Lake dropped in 2003, the Z. latifolia community has shown an expanding trend, which may have an important impact on the suitable habitats of migratory birds. However, their spatiotemporal dynamic and underlying driving mechanisms remain poorly understood. In this study, we developed a high-accuracy remote sensing extraction model by integrating multi-source data, taking advantage of the phenological characteristics and distinctive winter spectral features of Z. latifolia. We systematically analyzed the spatiotemporal dynamics of Z. latifolia communities in Poyang Lake from 1987 to 2023 and further examined their dominant driving factors. The results revealed that Z. latifolia communities were primarily distributed in the 12–14 m elevation zone of Poyang Lake and in dish-shaped lakes, with mean proportions of 62.9% and 66.2%, respectively, during the study period. From 1987 to 2023, their total area followed a pattern of “initial increase followed by decline”: sparsely distributed before 2003, expanding rapidly thereafter, peaking in 2018 (57.65 km2), and collapsing abruptly after 2020. Since 2003, the decline in water level of Poyang Lake has been significantly correlated with the rapid expansion of the Z. latifolia community, a pattern that indicates the former may be the main driving factor. In contrast, the extreme flood in 2020 and the subsequent frequent drought events were temporally synchronous with the rapid degradation of Z. latifolia communities, indicating that they may be the key environmental factors contributing to the degradation.These findings not only provide valuable data support for understanding the ecological evolution of Poyang Lake wetlands, but also offer important insights for their future conservation and adaptive management.
Zizania latifolia communities are a key wetland vegetation type in Poyang Lake, and their spatial distribution is significantly affected by the hydrological regimes of the lake. Since the water level of Poyang Lake dropped in 2003, the Z. latifolia community has shown an expanding trend, which may have an important impact on the suitable habitats of migratory birds. However, their spatiotemporal dynamic and underlying driving mechanisms remain poorly understood. In this study, we developed a high-accuracy remote sensing extraction model by integrating multi-source data, taking advantage of the phenological characteristics and distinctive winter spectral features of Z. latifolia. We systematically analyzed the spatiotemporal dynamics of Z. latifolia communities in Poyang Lake from 1987 to 2023 and further examined their dominant driving factors. The results revealed that Z. latifolia communities were primarily distributed in the 12–14 m elevation zone of Poyang Lake and in dish-shaped lakes, with mean proportions of 62.9% and 66.2%, respectively, during the study period. From 1987 to 2023, their total area followed a pattern of “initial increase followed by decline”: sparsely distributed before 2003, expanding rapidly thereafter, peaking in 2018 (57.65 km2), and collapsing abruptly after 2020. Since 2003, the decline in water level of Poyang Lake has been significantly correlated with the rapid expansion of the Z. latifolia community, a pattern that indicates the former may be the main driving factor. In contrast, the extreme flood in 2020 and the subsequent frequent drought events were temporally synchronous with the rapid degradation of Z. latifolia communities, indicating that they may be the key environmental factors contributing to the degradation.These findings not only provide valuable data support for understanding the ecological evolution of Poyang Lake wetlands, but also offer important insights for their future conservation and adaptive management.
Available online: December 23, 2025
Abstract:
The sustainable development of a river basin depends on the supply of ecosystem services in the river basin"s water ecosystem. Therefore, the health of river water ecosystems is an important guarantee. Taking the Weihe River Basin as the research area, this paper sorts out relevant domestic and foreign data and research results in 2004-2024 through bibliometrics, and deeply explores the water quality, habitat quality, biodiversity, and water ecology health of the Weihe River Basin. It summarizes the selection of water ecological health assessment indicators in the Weihe River Basin, clarifies the advantages, disadvantages, and applicable scopes of different water ecological health assessment methods. Based on these, we summarize the evolution law of water ecological health in the Weihe River Basin during 2004-2024. Overall, the water quality of the Weihe River has improved. The diversity of plankton and periphytic algae showed a downward trend in a certain period, but has shown a recovery trend in recent years. Water pollution and habitat destruction are the main factors threatening the water ecological health of the Weihe River Basin, especially the middle and lower reaches still have serious pollution problems. On this basis, combined with the ecological protection policies and regulations of the Weihe River Basin, the importance of water ecological environment management to water ecological health is evaluated. Finally, combined with the "Hanjiang-to-Weihe Water Transfer Project", the impact of increased water resources in the Weihe River Basin on water ecological health is prospected.
The sustainable development of a river basin depends on the supply of ecosystem services in the river basin"s water ecosystem. Therefore, the health of river water ecosystems is an important guarantee. Taking the Weihe River Basin as the research area, this paper sorts out relevant domestic and foreign data and research results in 2004-2024 through bibliometrics, and deeply explores the water quality, habitat quality, biodiversity, and water ecology health of the Weihe River Basin. It summarizes the selection of water ecological health assessment indicators in the Weihe River Basin, clarifies the advantages, disadvantages, and applicable scopes of different water ecological health assessment methods. Based on these, we summarize the evolution law of water ecological health in the Weihe River Basin during 2004-2024. Overall, the water quality of the Weihe River has improved. The diversity of plankton and periphytic algae showed a downward trend in a certain period, but has shown a recovery trend in recent years. Water pollution and habitat destruction are the main factors threatening the water ecological health of the Weihe River Basin, especially the middle and lower reaches still have serious pollution problems. On this basis, combined with the ecological protection policies and regulations of the Weihe River Basin, the importance of water ecological environment management to water ecological health is evaluated. Finally, combined with the "Hanjiang-to-Weihe Water Transfer Project", the impact of increased water resources in the Weihe River Basin on water ecological health is prospected.
Available online: December 18, 2025
Abstract:
Cyanobacterial blooms have emerged as a global environmental challenge threatening lake ecosystem security and drinking water safety. Timely prediction of bloom outbreaks is critical for implementing preventive measures and reducing disaster risks. To overcome the limitations of conventional mechanism-driven models, including their numerous parameters and computational complexity, this study established an machine learning framework that integrates multi-source monitoring data and remote sensing observations for Lake Chaohu. By integrating multi-site meteorological and water quality measurements with satellite-derived time-series data, we investigated the temporal cumulative effects of meteorological and water quality variables on cyanobacterial blooms. Based on the Random Forest (RF) model, two forecasting models were developed: one considering the temporal cumulative effects of variables (cumulative variable model) and the other using only single-day observations (single-day variable model), to achieve 1–7day (d) forecasts of bloom coverage area. Additionally, SHapley Additive exPlanations (SHAP) analysis was further applied to decode the model"s decision-making mechanisms, revealing feature contributions and nonlinear threshold behaviors. The results showed that: (1) Meteorological variables (air temperature, humidity, precipitation, and air pressure) exhibited longer cumulative effect durations (15~30 days) compared to water quality variables (nitrogen, phosphorus, and dissolved oxygen (1~10 days); (2) Cumulative-variable models demonstrated superior predictive accuracy (R2 = 0.7~0.8) over single-day variable models (R2 = 0.4~0.6), with optimal 1-day ahead performance (R2 = 0.79, RMSE = 35.36 km2); (3) Critical thresholds were identified at average temperature approximately > 23°C, maximum wind speed approximately < 4 m/s, precipitation approximately > 200 mm, nitrogen-phosphorus ratio approximately < 15, pH > 8.5, and dissolved oxygen approximately < 8.9 mg/L. The proposed method enables high-precision short-term forecasting using multi-station monitoring data, holding promise for providing a transferable decision support framework for eutrophic lake management.
Cyanobacterial blooms have emerged as a global environmental challenge threatening lake ecosystem security and drinking water safety. Timely prediction of bloom outbreaks is critical for implementing preventive measures and reducing disaster risks. To overcome the limitations of conventional mechanism-driven models, including their numerous parameters and computational complexity, this study established an machine learning framework that integrates multi-source monitoring data and remote sensing observations for Lake Chaohu. By integrating multi-site meteorological and water quality measurements with satellite-derived time-series data, we investigated the temporal cumulative effects of meteorological and water quality variables on cyanobacterial blooms. Based on the Random Forest (RF) model, two forecasting models were developed: one considering the temporal cumulative effects of variables (cumulative variable model) and the other using only single-day observations (single-day variable model), to achieve 1–7day (d) forecasts of bloom coverage area. Additionally, SHapley Additive exPlanations (SHAP) analysis was further applied to decode the model"s decision-making mechanisms, revealing feature contributions and nonlinear threshold behaviors. The results showed that: (1) Meteorological variables (air temperature, humidity, precipitation, and air pressure) exhibited longer cumulative effect durations (15~30 days) compared to water quality variables (nitrogen, phosphorus, and dissolved oxygen (1~10 days); (2) Cumulative-variable models demonstrated superior predictive accuracy (R2 = 0.7~0.8) over single-day variable models (R2 = 0.4~0.6), with optimal 1-day ahead performance (R2 = 0.79, RMSE = 35.36 km2); (3) Critical thresholds were identified at average temperature approximately > 23°C, maximum wind speed approximately < 4 m/s, precipitation approximately > 200 mm, nitrogen-phosphorus ratio approximately < 15, pH > 8.5, and dissolved oxygen approximately < 8.9 mg/L. The proposed method enables high-precision short-term forecasting using multi-station monitoring data, holding promise for providing a transferable decision support framework for eutrophic lake management.
Available online: December 18, 2025
Abstract:
The surface water resources in the Dongting Lake Basin play an important role in maintaining ecosystems, protecting biodiversity, and regulating the climate, but they are vulnerable to the impacts of climate change and human activities. Although extensive studies have been conducted on the dynamic changes in the surface water area of the Dongting Lake Basin, most of the existing research results lack long-term and whole-basin analyses. Moreover, the driving mechanisms are mainly based on qualitative descriptions, and spatial analyses are also limited to the main lake area. Based on this, this study aims to reveal the spatiotemporal evolution patterns of the surface water area in the entire Dongting Lake Basin and its sub-basins, clarify the contributions of climatic factors and human activities to the dynamics of surface water, and explore the migration patterns of the centroid of surface water distribution in the sub-basins. By comprehensively utilizing multi-source remote sensing satellite data and the JRC Global Surface Water Dataset products, and adopting methods such as the Mann-Kendall test, Pettitt test, Pearson correlation test, and centroid analysis model, this study analyzes and obtains the spatiotemporal variation patterns and main driving factors of the surface water area in the Dongting Lake Basin from 1990 to 2021. The results show that:①Over the past 30 years, the surface water area of the Dongting Lake Basin has shown an increasing trend, with the Yuanjiang River system being the most significant and it has increased by 420.07%, showing obvious spatial differences, and presenting a three-stage characteristic of "rapid expansion - fluctuating reduction - recovery growth" in terms of time;②The centroid of the surface water distribution in the Dongting Lake Basin has shifted southwestward overall, and the fluctuation range is mainly reflected in the east-west displacement, with a displacement of 19.56 km. The centroid migration of each sub-basin is directly related to the spatial characteristics of regional water conservancy project construction and ecological restoration, reflecting the remodeling effect of human activities on the spatial pattern of surface water;③Precipitation is the main climatic factor causing the increase in the surface water area of the Dongting Lake Basin, while human engineering regulation and ecological restoration measures such as water conservancy project construction and "returning farmland to lakes" have significantly changed the spatial distribution pattern of surface water in the basin;④Climate change contributes approximately 40%-55% to the changes in the surface water area of the Dongting Lake Basin, while human engineering regulation and ecological restoration measures such as water conservancy project construction and "returning farmland to lakes" not only significantly change the spatial distribution pattern of surface water in the basin, but also have a contribution degree of 45%-60%, becoming the dominant driving force. This study will help understand the long-term variation patterns of surface water resources in the Dongting Lake Basin and is of great significance for formulating scientific and reasonable ecosystem protection and restoration measures.
The surface water resources in the Dongting Lake Basin play an important role in maintaining ecosystems, protecting biodiversity, and regulating the climate, but they are vulnerable to the impacts of climate change and human activities. Although extensive studies have been conducted on the dynamic changes in the surface water area of the Dongting Lake Basin, most of the existing research results lack long-term and whole-basin analyses. Moreover, the driving mechanisms are mainly based on qualitative descriptions, and spatial analyses are also limited to the main lake area. Based on this, this study aims to reveal the spatiotemporal evolution patterns of the surface water area in the entire Dongting Lake Basin and its sub-basins, clarify the contributions of climatic factors and human activities to the dynamics of surface water, and explore the migration patterns of the centroid of surface water distribution in the sub-basins. By comprehensively utilizing multi-source remote sensing satellite data and the JRC Global Surface Water Dataset products, and adopting methods such as the Mann-Kendall test, Pettitt test, Pearson correlation test, and centroid analysis model, this study analyzes and obtains the spatiotemporal variation patterns and main driving factors of the surface water area in the Dongting Lake Basin from 1990 to 2021. The results show that:①Over the past 30 years, the surface water area of the Dongting Lake Basin has shown an increasing trend, with the Yuanjiang River system being the most significant and it has increased by 420.07%, showing obvious spatial differences, and presenting a three-stage characteristic of "rapid expansion - fluctuating reduction - recovery growth" in terms of time;②The centroid of the surface water distribution in the Dongting Lake Basin has shifted southwestward overall, and the fluctuation range is mainly reflected in the east-west displacement, with a displacement of 19.56 km. The centroid migration of each sub-basin is directly related to the spatial characteristics of regional water conservancy project construction and ecological restoration, reflecting the remodeling effect of human activities on the spatial pattern of surface water;③Precipitation is the main climatic factor causing the increase in the surface water area of the Dongting Lake Basin, while human engineering regulation and ecological restoration measures such as water conservancy project construction and "returning farmland to lakes" have significantly changed the spatial distribution pattern of surface water in the basin;④Climate change contributes approximately 40%-55% to the changes in the surface water area of the Dongting Lake Basin, while human engineering regulation and ecological restoration measures such as water conservancy project construction and "returning farmland to lakes" not only significantly change the spatial distribution pattern of surface water in the basin, but also have a contribution degree of 45%-60%, becoming the dominant driving force. This study will help understand the long-term variation patterns of surface water resources in the Dongting Lake Basin and is of great significance for formulating scientific and reasonable ecosystem protection and restoration measures.
Available online: November 26, 2025
Abstract:
As the largest freshwater lake in Yunnan, Dianchi Lake plays a critical role in regional ecological security, with its area, morphology, and surrounding land-use patterns undergoing significant transformations. This study integrates multi-source data—including historical topographic maps, aerial surveys, Keyhole reconnaissance satellite imagery, and Landsat satellite images (1920s–2023)—to construct a century-scale dataset of Dianchi Lake’s area and morphological changes. We analyze the spatiotemporal evolution of its water extent through a dual-method framework: Semi-automatic water reconstruction for the pre-1985 era (lacking satellite imagery) using historical maps and aerial photos; Automated water extraction for 1985–2023 based on Landsat-derived water indices. Key findings reveal: (1) Policy-driven area fluctuations: Water area declined overall from 1920 to 2012 but rebounded after 2012 due to ecological restoration; (2) Morphological complexity: Area decreased by 8.55%, while perimeter increased by 10.44%. The circularity index declined by 26.31%, and the shoreline development coefficient rose by 15.58%; (3) Anthropogenic dominance: Shoreline types shifted from natural-agricultural to artificial, with artificial shorelines increasing 16-fold (1985–2020) and agricultural shorelines decreasing by 44.53%. Extreme drought events accelerated short-term shrinkage.
As the largest freshwater lake in Yunnan, Dianchi Lake plays a critical role in regional ecological security, with its area, morphology, and surrounding land-use patterns undergoing significant transformations. This study integrates multi-source data—including historical topographic maps, aerial surveys, Keyhole reconnaissance satellite imagery, and Landsat satellite images (1920s–2023)—to construct a century-scale dataset of Dianchi Lake’s area and morphological changes. We analyze the spatiotemporal evolution of its water extent through a dual-method framework: Semi-automatic water reconstruction for the pre-1985 era (lacking satellite imagery) using historical maps and aerial photos; Automated water extraction for 1985–2023 based on Landsat-derived water indices. Key findings reveal: (1) Policy-driven area fluctuations: Water area declined overall from 1920 to 2012 but rebounded after 2012 due to ecological restoration; (2) Morphological complexity: Area decreased by 8.55%, while perimeter increased by 10.44%. The circularity index declined by 26.31%, and the shoreline development coefficient rose by 15.58%; (3) Anthropogenic dominance: Shoreline types shifted from natural-agricultural to artificial, with artificial shorelines increasing 16-fold (1985–2020) and agricultural shorelines decreasing by 44.53%. Extreme drought events accelerated short-term shrinkage.
