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2026,38(2):435-447, DOI: 10.18307/2026.0200
Abstract:
Assessments of the ecological condition of Chinese waterbodies have increased substantially in recent years; however, the field is still in an early developmental stage, facing challenges such as an incomplete theoretical framework, imprecise methods, and limited comparability across studies. To advance scientific progress in China by leveraging mature international experience, this review synthesizes the role of ecological theory in guiding aquatic ecological assessments and provides recommendations for its application. The theoretical foundation of these assessments lies in biota-environment relationships, with niche and community-assembly (metacommunity) theories being particularly influential in shaping assessment paradigms, optimizing indices, and improving assessment performance (i.e., the effectiveness in indicating anthropogenic disturbance). Methodologically, assessment approaches have evolved from early physico-chemistry-based evaluations to a contemporary paradigm centered on biological assessment, supported by physico-chemical measures. Diagnostic frameworks that integrate quantitative condition assessment with stressor identification now represent the prevailing approach. In developing assessment indices, there is increasing emphasis on biological functional traits as sensitive metrics, leading to the widespread adoption of multimetric indices that integrate disturbance-tolerant taxa, biodiversity, and functional traits. The performance of these methods is typically evaluated across several dimensions: precision, bias, responsiveness, sensitivity, and consistency. To enhance performance, standardized survey and analytical procedures are essential, alongside the use of anthropogenic disturbance gradients to define reference conditions and predictive models to account for natural variability. Despite these advances, the ecological foundations for setting reference conditions and ecological class criteria, as well as for stressor diagnosis, require further development. International experience underscores that robust aquatic ecological assessment must be grounded in ecological theories. For China, future efforts should prioritize accounting for natural variability, empirically selecting metrics from survey data, and implementing diagnostic frameworks that explicitly link ecological condition to causal stressors. Advancing these elements will consolidate the scientific foundation of aquatic assessment, promoting a transition toward greater precision, standardization, and automation, thereby providing stronger support for aquatic ecological management and international environmental commitments.
Assessments of the ecological condition of Chinese waterbodies have increased substantially in recent years; however, the field is still in an early developmental stage, facing challenges such as an incomplete theoretical framework, imprecise methods, and limited comparability across studies. To advance scientific progress in China by leveraging mature international experience, this review synthesizes the role of ecological theory in guiding aquatic ecological assessments and provides recommendations for its application. The theoretical foundation of these assessments lies in biota-environment relationships, with niche and community-assembly (metacommunity) theories being particularly influential in shaping assessment paradigms, optimizing indices, and improving assessment performance (i.e., the effectiveness in indicating anthropogenic disturbance). Methodologically, assessment approaches have evolved from early physico-chemistry-based evaluations to a contemporary paradigm centered on biological assessment, supported by physico-chemical measures. Diagnostic frameworks that integrate quantitative condition assessment with stressor identification now represent the prevailing approach. In developing assessment indices, there is increasing emphasis on biological functional traits as sensitive metrics, leading to the widespread adoption of multimetric indices that integrate disturbance-tolerant taxa, biodiversity, and functional traits. The performance of these methods is typically evaluated across several dimensions: precision, bias, responsiveness, sensitivity, and consistency. To enhance performance, standardized survey and analytical procedures are essential, alongside the use of anthropogenic disturbance gradients to define reference conditions and predictive models to account for natural variability. Despite these advances, the ecological foundations for setting reference conditions and ecological class criteria, as well as for stressor diagnosis, require further development. International experience underscores that robust aquatic ecological assessment must be grounded in ecological theories. For China, future efforts should prioritize accounting for natural variability, empirically selecting metrics from survey data, and implementing diagnostic frameworks that explicitly link ecological condition to causal stressors. Advancing these elements will consolidate the scientific foundation of aquatic assessment, promoting a transition toward greater precision, standardization, and automation, thereby providing stronger support for aquatic ecological management and international environmental commitments.
2026,38(2):448-464, DOI: 10.18307/2026.0201
Abstract:
As emerging environmental contaminants, ensuring the security of water supplies requires a critical understanding of the occurrence, transmission mechanisms and risk control of antibiotic resistance genes (ARGs) in basin water environments. This paper provides a systematic review of the characteristics of the occurrence, pollution sources and spatiotemporal distribution patterns of ARGs in China’s seven major river basins: the Yangtze, Yellow, Huaihe, Pearl, Haihe, Liaohe and Songhua rivers. The paper also analyses the migration and diffusion mechanisms of ARGs in combination with the effects of combined pollution from eutrophication, heavy metals, and emerging contaminants (e.g., antibiotics, microplastics, endocrine-disrupting chemicals, and persistent organic pollutants). The study reveals that sulfonamides, tetracyclines, and aminoglycosides dominate ARGs in China’s basin water environments, primarily originating from non-point source pollution (e.g. agricultural planting and livestock and poultry farming) and point source emissions (e.g., wastewater treatment plant effluents and medical wastewater). In terms of occurrence levels, the absolute abundances of ARGs in sediments (106-1010 copies/g) are generally three orders of magnitude higher than in water bodies (103-107 copies/mL), although their relative abundances (copies/16S rRNA) are similar. Spatiotemporally, ARGs are driven by microbial communities, environmental physicochemical factors, human activities and mobile genetic elements (MGEs), with microbial communities exerting the most significant influence. In terms of the effects of pollution, water eutrophication promotes the proliferation of bacterial communities that host ARGs, such as nitrate-reducing bacteria. This results in a significant positive correlation between ARG abundances and total nitrogen and total phosphorus loads. Heavy metals (e.g., copper, zinc and nickel) enhance the efficiency of ARG conjugative transfer through co-selection effects. Emerging contaminants such as antibiotics exert selective pressure on ARGs, while microplastic biofilms can increase ARG transformation frequencies by up to 1000-fold compared to natural substrates. Endocrine-disrupting chemicals (e.g., bisphenol A) and persistent organic pollutants (e.g. perfluorooctanoic acid) promote ARG horizontal transfer by inducing oxidative stress or upregulating plasmid expression. ARG transmission mechanisms primarily include shaping of the bacterial community (e.g., selective enrichment ofFirmicutes andProteobacteria), conjugative transfer (dependent on MGEs and ATP energy metabolism), induced transformation (extracellular DNA adsorption onto suspended particulates) and phage-mediated transfer (preferential packaging of ARG fragments). Notably, fluvial sediment dynamics processes such as suspended sediment transport and resuspension significantly influence ARG transmission fluxes by regulating pollutant partitioning across phases. Future research should investigate the coupled processes of “sediment-water dynamics-contaminants-ARGs”, analyse the cross-scale regulatory mechanisms of ARGs in multi-phase water environments and explore the potential application of sediment-water ecological regulation in ARG risk management.
As emerging environmental contaminants, ensuring the security of water supplies requires a critical understanding of the occurrence, transmission mechanisms and risk control of antibiotic resistance genes (ARGs) in basin water environments. This paper provides a systematic review of the characteristics of the occurrence, pollution sources and spatiotemporal distribution patterns of ARGs in China’s seven major river basins: the Yangtze, Yellow, Huaihe, Pearl, Haihe, Liaohe and Songhua rivers. The paper also analyses the migration and diffusion mechanisms of ARGs in combination with the effects of combined pollution from eutrophication, heavy metals, and emerging contaminants (e.g., antibiotics, microplastics, endocrine-disrupting chemicals, and persistent organic pollutants). The study reveals that sulfonamides, tetracyclines, and aminoglycosides dominate ARGs in China’s basin water environments, primarily originating from non-point source pollution (e.g. agricultural planting and livestock and poultry farming) and point source emissions (e.g., wastewater treatment plant effluents and medical wastewater). In terms of occurrence levels, the absolute abundances of ARGs in sediments (106-1010 copies/g) are generally three orders of magnitude higher than in water bodies (103-107 copies/mL), although their relative abundances (copies/16S rRNA) are similar. Spatiotemporally, ARGs are driven by microbial communities, environmental physicochemical factors, human activities and mobile genetic elements (MGEs), with microbial communities exerting the most significant influence. In terms of the effects of pollution, water eutrophication promotes the proliferation of bacterial communities that host ARGs, such as nitrate-reducing bacteria. This results in a significant positive correlation between ARG abundances and total nitrogen and total phosphorus loads. Heavy metals (e.g., copper, zinc and nickel) enhance the efficiency of ARG conjugative transfer through co-selection effects. Emerging contaminants such as antibiotics exert selective pressure on ARGs, while microplastic biofilms can increase ARG transformation frequencies by up to 1000-fold compared to natural substrates. Endocrine-disrupting chemicals (e.g., bisphenol A) and persistent organic pollutants (e.g. perfluorooctanoic acid) promote ARG horizontal transfer by inducing oxidative stress or upregulating plasmid expression. ARG transmission mechanisms primarily include shaping of the bacterial community (e.g., selective enrichment ofFirmicutes andProteobacteria), conjugative transfer (dependent on MGEs and ATP energy metabolism), induced transformation (extracellular DNA adsorption onto suspended particulates) and phage-mediated transfer (preferential packaging of ARG fragments). Notably, fluvial sediment dynamics processes such as suspended sediment transport and resuspension significantly influence ARG transmission fluxes by regulating pollutant partitioning across phases. Future research should investigate the coupled processes of “sediment-water dynamics-contaminants-ARGs”, analyse the cross-scale regulatory mechanisms of ARGs in multi-phase water environments and explore the potential application of sediment-water ecological regulation in ARG risk management.
2026,38(2):465-481, DOI: 10.18307/2026.0202
Abstract:
Nitrogen fixation is a vital process in biogeochemical cycles within ecosystems. While current research on nitrogen fixation in aquatic ecosystems has mainly focused on marine environments, studies on waters, such as lakes, have only recently begun. To understand current research hotspots and development trends regarding nitrogen-fixing microorganisms in freshwater lakes, this study examined literature on the topic from the Web of Science database. CiteSpace and VOSviewer were used to construct and analyze knowledge maps, revealing current research hotspots and future research trends in this field. Based on these findings, we conducted a literature integration analysis to outline the effects of nitrogen and phosphorus nutrients on nitrogen fixation rates in water and their underlying mechanisms. The results show that: (1) From 1992 to 2024, the number of publications and citations in the field of nitrogen-fixing microorganisms in global freshwater lakes has steadily increased. (2) National, author and institutional collaboration network analyses indicate that research on nitrogen-fixing microorganisms in freshwater lakes is an interdisciplinary field involving cooperation among multiple countries and institutions. (3)Cluster analysis reveals that research hotspots mainly focus on: nutrient control strategies under phosphorus limitation and their impact on cyanobacterial community succession; the analysis of nitrogen-fixing microbial diversity based on thenifH gene; and the functional characterization of this gene in the nitrogen cycle. The analysis also reveals long-term dynamic changes in phytoplankton community composition driven by environmental factors. (4) The results of the integration analysis indicate that: the geographical distribution of nitrogen fixation quantification studies is imbalanced. North America has established a comprehensive indicator system covering various water types. In contrast, Asia and South America focus on describing cyanobacterial biomass, while Europe primarily focuses on the dynamic changes of nitrogen and phosphorus, as well as the coupling relationship of the nitrogen fixation process. Research on nitrogen-fixing species mainly centres on the phylum Cyanobacteria (e.g.,Nostoc andDolichospermum), while other phyla such as Proteobacteria and Archaea are relatively scarce. Total phosphorus shows a significant positive correlation with nitrogen fixation rates, whereas total dissolved nitrogen, nitrate nitrogen and ammonium nitrogen show significant negative correlations. Non-linear segmented model fitting revealed a critical value of 25μg/L for total phosphorus in regulating nitrogen fixation rates in freshwater lakes. Future research on nitrogen fixation processes urgently requires standardised measurement methods (e.g., acetylene reduction and isotope tracing) and metric units (e.g., area/volume) to improve the comparability of research results. This study summarises changes in the research hotspots and frontiers of nitrogen-fixing microorganisms in freshwater lakes over the past 30 years, suggesting that our understanding of nitrogen fixation processes and their ecological contributions should continue to expand by incorporating diverse analytical indicators (e.g., enzyme activity and transcriptomics), standardized analytical procedures and multi-indicator fusion evaluation methods.
Nitrogen fixation is a vital process in biogeochemical cycles within ecosystems. While current research on nitrogen fixation in aquatic ecosystems has mainly focused on marine environments, studies on waters, such as lakes, have only recently begun. To understand current research hotspots and development trends regarding nitrogen-fixing microorganisms in freshwater lakes, this study examined literature on the topic from the Web of Science database. CiteSpace and VOSviewer were used to construct and analyze knowledge maps, revealing current research hotspots and future research trends in this field. Based on these findings, we conducted a literature integration analysis to outline the effects of nitrogen and phosphorus nutrients on nitrogen fixation rates in water and their underlying mechanisms. The results show that: (1) From 1992 to 2024, the number of publications and citations in the field of nitrogen-fixing microorganisms in global freshwater lakes has steadily increased. (2) National, author and institutional collaboration network analyses indicate that research on nitrogen-fixing microorganisms in freshwater lakes is an interdisciplinary field involving cooperation among multiple countries and institutions. (3)Cluster analysis reveals that research hotspots mainly focus on: nutrient control strategies under phosphorus limitation and their impact on cyanobacterial community succession; the analysis of nitrogen-fixing microbial diversity based on thenifH gene; and the functional characterization of this gene in the nitrogen cycle. The analysis also reveals long-term dynamic changes in phytoplankton community composition driven by environmental factors. (4) The results of the integration analysis indicate that: the geographical distribution of nitrogen fixation quantification studies is imbalanced. North America has established a comprehensive indicator system covering various water types. In contrast, Asia and South America focus on describing cyanobacterial biomass, while Europe primarily focuses on the dynamic changes of nitrogen and phosphorus, as well as the coupling relationship of the nitrogen fixation process. Research on nitrogen-fixing species mainly centres on the phylum Cyanobacteria (e.g.,Nostoc andDolichospermum), while other phyla such as Proteobacteria and Archaea are relatively scarce. Total phosphorus shows a significant positive correlation with nitrogen fixation rates, whereas total dissolved nitrogen, nitrate nitrogen and ammonium nitrogen show significant negative correlations. Non-linear segmented model fitting revealed a critical value of 25μg/L for total phosphorus in regulating nitrogen fixation rates in freshwater lakes. Future research on nitrogen fixation processes urgently requires standardised measurement methods (e.g., acetylene reduction and isotope tracing) and metric units (e.g., area/volume) to improve the comparability of research results. This study summarises changes in the research hotspots and frontiers of nitrogen-fixing microorganisms in freshwater lakes over the past 30 years, suggesting that our understanding of nitrogen fixation processes and their ecological contributions should continue to expand by incorporating diverse analytical indicators (e.g., enzyme activity and transcriptomics), standardized analytical procedures and multi-indicator fusion evaluation methods.
2026,38(2):482-495, DOI: 10.18307/2026.0210
Abstract:
The remote sensing inversion of riverine algal blooms is frequently compromised by boundary effects from riparian wetlands, and the accuracy of traditional methods remains limited in narrow, elongated water bodies. As a typical sensitive water area, the terminal reach of the Ganjiang River still lacks a clear understanding of its algal bloom outbreak mechanisms. Utilizing Sentinel-2 and Landsat series satellite data, this study developed an improved method that integrates inward-masking technology with the floating algae index (FAI) and Otsu’s threshold to effectively suppress nearshore interference and accurately extract bloom extents in elongated rivers. Applying this method, we reconstructed the algal bloom outbreak processes in the Ganjiang River from 2019 to 2024. The results indicated that blooms exhibited pronounced seasonality, occurringprimarily in late summer and early autumn (August-September). Spatially, they were significantly aggregated in nearshore slow-flowing zones along the windward banks of the southern and middle branches, with intensity gradually decreasing from the littoral zone toward the thalweg. Driver analysis using a Random Forest regression model revealed that daily maximum temperature was extremely significantly correlated with bloom area, contributing 47.1%—far exceeding the contributions of nutrients (29.9%), mean daily wind speed (9.3%), mean daily discharge (7.3%), and daily rainfall (6.4%). Furthermore, by analyzing bloom dynamics and environmental conditions during typical heatwave events (≥35 ℃ for three consecutive days), this study demonstrates that under meso-eutrophic conditions, low discharge and water retention during summer and autumn form the basis for bloom accumulation, while extreme heatwaves act as dominant drivers. Their coupling with low discharge and nutrient availability significantly amplifies the scale of bloom outbreaks. This study provides valuable insights into the mechanisms governing riverine algal bloom outbreaks.
The remote sensing inversion of riverine algal blooms is frequently compromised by boundary effects from riparian wetlands, and the accuracy of traditional methods remains limited in narrow, elongated water bodies. As a typical sensitive water area, the terminal reach of the Ganjiang River still lacks a clear understanding of its algal bloom outbreak mechanisms. Utilizing Sentinel-2 and Landsat series satellite data, this study developed an improved method that integrates inward-masking technology with the floating algae index (FAI) and Otsu’s threshold to effectively suppress nearshore interference and accurately extract bloom extents in elongated rivers. Applying this method, we reconstructed the algal bloom outbreak processes in the Ganjiang River from 2019 to 2024. The results indicated that blooms exhibited pronounced seasonality, occurringprimarily in late summer and early autumn (August-September). Spatially, they were significantly aggregated in nearshore slow-flowing zones along the windward banks of the southern and middle branches, with intensity gradually decreasing from the littoral zone toward the thalweg. Driver analysis using a Random Forest regression model revealed that daily maximum temperature was extremely significantly correlated with bloom area, contributing 47.1%—far exceeding the contributions of nutrients (29.9%), mean daily wind speed (9.3%), mean daily discharge (7.3%), and daily rainfall (6.4%). Furthermore, by analyzing bloom dynamics and environmental conditions during typical heatwave events (≥35 ℃ for three consecutive days), this study demonstrates that under meso-eutrophic conditions, low discharge and water retention during summer and autumn form the basis for bloom accumulation, while extreme heatwaves act as dominant drivers. Their coupling with low discharge and nutrient availability significantly amplifies the scale of bloom outbreaks. This study provides valuable insights into the mechanisms governing riverine algal bloom outbreaks.
2026,38(2):496-511, DOI: 10.18307/2026.0211
Abstract:
Over the years, integrated remediation efforts in Lake Dianchi have yielded significant interim success in curbing cyanobacterial blooms. From 2018 onward, both the frequency and spatial extent of these blooms showed a consistent downward trend. However, a marked resurgence was observed in 2023, prompting renewed scientific and public concern. This study systematically investigates the variability and outbreak mechanisms of cyanobacterial blooms in Lake Dianchi from 2018 to 2023, leveraging MODIS satellite imagery alongside integrated water quality and meteorological monitoring data. Analysis of the monitoring data reveals that the annual bloom frequency followed a “V”-shaped trajectory over the six-year period, with 2023 registering a notably high frequency of 87.0%, significantly exceeding the six-year average of 69.3%. In contrast, the average bloom area from 2022 to 2023 was substantially lower than that from 2018 to 2021. Specifically, the average bloom area in 2023 (15.86 km2) was 65.3% below the six-year mean, although it represented an 11.4% increase from 2022. Spearman correlation analysis demonstrated that both monthly bloom frequency and monthly average bloom area were significantly positively correlated with monthly average temperature and monthly precipitation, while showing a significant negative correlation with monthly average wind speed. Additionally, the monthly average cyanobacterial density exhibited a strong positive correlation with the monthly average total phosphorus concentration. Multivariate linear regression analysis highlighted air temperature and wind speed as the dominant meteorological drivers of bloom dynamics in Lake Dianchi. However, total phosphorus concentration had limited explanatory power regarding variations in algal density. Throughout the 2018-2023 period, cyanobacterial density consistently surpassed the mild bloom threshold (1.0×107 cells/L), suggesting that the 2023 resurgence was primarily driven by synergistic meteorological influences. During the non-bloom season (January-May and December), an increased proportion of temperatures between 13-20 ℃ accelerated cyanobacterial resurgence. During the bloom season (June-November), the increase in the proportion of low wind speeds (＜2 m/s) promoted cyanobacterial surfacing and aggregation. A reduced proportion of temperatures below 13 ℃ favored cyanobacterial growth. A significant rise in the proportion of 20-25 ℃ temperatures during the bloom season likely enhanced cyanobacterial buoyancy, contributing to the broader bloom coverage observed in 2023. These findings offer valuable theoretical support for the daily prevention, prediction, and early warning systems for cyanobacterial blooms in Lake Dianchi. Furthermore, they provide a reference for bloom management in other plateau lakes across Yunnan Province.
Over the years, integrated remediation efforts in Lake Dianchi have yielded significant interim success in curbing cyanobacterial blooms. From 2018 onward, both the frequency and spatial extent of these blooms showed a consistent downward trend. However, a marked resurgence was observed in 2023, prompting renewed scientific and public concern. This study systematically investigates the variability and outbreak mechanisms of cyanobacterial blooms in Lake Dianchi from 2018 to 2023, leveraging MODIS satellite imagery alongside integrated water quality and meteorological monitoring data. Analysis of the monitoring data reveals that the annual bloom frequency followed a “V”-shaped trajectory over the six-year period, with 2023 registering a notably high frequency of 87.0%, significantly exceeding the six-year average of 69.3%. In contrast, the average bloom area from 2022 to 2023 was substantially lower than that from 2018 to 2021. Specifically, the average bloom area in 2023 (15.86 km2) was 65.3% below the six-year mean, although it represented an 11.4% increase from 2022. Spearman correlation analysis demonstrated that both monthly bloom frequency and monthly average bloom area were significantly positively correlated with monthly average temperature and monthly precipitation, while showing a significant negative correlation with monthly average wind speed. Additionally, the monthly average cyanobacterial density exhibited a strong positive correlation with the monthly average total phosphorus concentration. Multivariate linear regression analysis highlighted air temperature and wind speed as the dominant meteorological drivers of bloom dynamics in Lake Dianchi. However, total phosphorus concentration had limited explanatory power regarding variations in algal density. Throughout the 2018-2023 period, cyanobacterial density consistently surpassed the mild bloom threshold (1.0×107 cells/L), suggesting that the 2023 resurgence was primarily driven by synergistic meteorological influences. During the non-bloom season (January-May and December), an increased proportion of temperatures between 13-20 ℃ accelerated cyanobacterial resurgence. During the bloom season (June-November), the increase in the proportion of low wind speeds (＜2 m/s) promoted cyanobacterial surfacing and aggregation. A reduced proportion of temperatures below 13 ℃ favored cyanobacterial growth. A significant rise in the proportion of 20-25 ℃ temperatures during the bloom season likely enhanced cyanobacterial buoyancy, contributing to the broader bloom coverage observed in 2023. These findings offer valuable theoretical support for the daily prevention, prediction, and early warning systems for cyanobacterial blooms in Lake Dianchi. Furthermore, they provide a reference for bloom management in other plateau lakes across Yunnan Province.
2026,38(2):512-526, DOI: 10.18307/2026.0212
Abstract:
To investigate the spatiotemporal distribution patterns of phytoplankton communities and their driving factors within the Shichuan River Basin, four systematic aquatic ecological surveys were conducted across the main stream of the Shichuan River, three tributaries, and three reservoirs during February (winter) and May (spring) of 2022, and August (summer) and November (autumn) of 2023. A total of 211 phytoplankton species were identified, spanning 78 genera and 7 phyla. Bacillariophyta constituted the highest proportion at 44.08%, followed by Chlorophyta at 31.75%. Dominant species across all four seasons includedCyclotella meneghiniana,Fragilaria acus,Navicula simples,Nitzschia palea, andChlorella ellipsoidea(Y＞0.1). Phytoplankton cell density ranged from 49.90×104 to 631.67×104 cells/L, with an average of 196.57×104 cells/L. Biomass varied between 1.38 and 18.02 mg/L, averaging 4.84 mg/L. The Shannon-Wiener diversity index and Margalef richness index peaked in spring. Significant differences in diversity indices were observed among different water bodies. Average phytoplankton diversity indices in the main and tributary streams exceeded those in reservoirs across all seasons. Redundancy analysis revealed that nitrogen and phosphorus nutrients, along with dissolved oxygen, were the primary environmental factors influencing dominant species distribution in the main and tributary streams. In contrast, water depth was the dominant factor in reservoirs. Structural equation modelingindicated that land use types within the 1000 m riparian buffer zone—specifically cultivated land, forest land, and construction land—indirectly influence chlorophyll-a concentrations by modulating nitrogen and phosphorus levels in the water. Compared to reservoirs, chemical factors in river systems exhibited a more pronounced effect on chlorophyll-a concentrations.
To investigate the spatiotemporal distribution patterns of phytoplankton communities and their driving factors within the Shichuan River Basin, four systematic aquatic ecological surveys were conducted across the main stream of the Shichuan River, three tributaries, and three reservoirs during February (winter) and May (spring) of 2022, and August (summer) and November (autumn) of 2023. A total of 211 phytoplankton species were identified, spanning 78 genera and 7 phyla. Bacillariophyta constituted the highest proportion at 44.08%, followed by Chlorophyta at 31.75%. Dominant species across all four seasons includedCyclotella meneghiniana,Fragilaria acus,Navicula simples,Nitzschia palea, andChlorella ellipsoidea(Y＞0.1). Phytoplankton cell density ranged from 49.90×104 to 631.67×104 cells/L, with an average of 196.57×104 cells/L. Biomass varied between 1.38 and 18.02 mg/L, averaging 4.84 mg/L. The Shannon-Wiener diversity index and Margalef richness index peaked in spring. Significant differences in diversity indices were observed among different water bodies. Average phytoplankton diversity indices in the main and tributary streams exceeded those in reservoirs across all seasons. Redundancy analysis revealed that nitrogen and phosphorus nutrients, along with dissolved oxygen, were the primary environmental factors influencing dominant species distribution in the main and tributary streams. In contrast, water depth was the dominant factor in reservoirs. Structural equation modelingindicated that land use types within the 1000 m riparian buffer zone—specifically cultivated land, forest land, and construction land—indirectly influence chlorophyll-a concentrations by modulating nitrogen and phosphorus levels in the water. Compared to reservoirs, chemical factors in river systems exhibited a more pronounced effect on chlorophyll-a concentrations.
2026,38(2):527-539, DOI: 10.18307/2026.0213
Abstract:
Algae are crucial primary producers in lake ecosystems, and their biomass and community structure can reflect water pollution and ecological status. As an important component of algae, the species composition characteristics of diatoms are also sensitive indicators for evaluating lake environmental quality. However, there is still a lack of systematic analysis regarding whether there are significant differences in the variation patterns and response mechanisms of algal biomass and diatom communities in lakes with different pollution levels. This study conducted seasonal investigations and comparative analyses in Lake Datun and Lake Yangzong, which have relatively high arsenic (As) pollution levels, and Lake Yilong, which is not affected by arsenic pollution, in Yunnan Province. The aim was to identify the main characteristics, driving factors, and key processes of algal changes 〖JP2〗under different arsenic pollution levels. Among the 55 surface water samples collected in this study, the concentration of water chlorophyll-a (Chl.a), which indicates algal biomass, was the highest in the eutrophic Lake Datun. Diatom compositions differed among the lakes and showed obvious seasonal fluctuations. Correlation analysis revealed a significant positive correlation between arsenic and Chl.aconcentrations in the lakes. This outcome indicates that phytoplankton are sensitive to arsenic stress in these lakes, and that the low arsenic levels exert a notable stimulating effect on algal growth. Meanwhile, arsenic was also significantly correlated with the main direction of diatom community changes. The results of variance decomposition analysis on algal data and environmental factors from the three lakes showed that the driving effect of the main environmental gradients on the succession of diatom community structure (PC1 index) was more significant than the fluctuation of Chl.a concentration (with average explained variances of 64.1% and 39.8%, respectively). The study results also revealed that the seasonal variation of water arsenic pollution is closely related to water temperature and lake depth type: increased water temperature promotes the chemical activity of arsenic and increases water arsenic concentration in shallow lakes, while in deep lakes, it limits the diffusion of sediment arsenic and the vertical migration of water arsenic through thermal stratification. In conclusion, the interactions between arsenic and factors such as water temperature, nutrients, and water depth under different pollution levels are significant, exerting important influences on the seasonal changes of algae and leading to large differences in the response intensities of different algal indicators. Therefore, for effective ecological assessment and restoration of lake arsenic pollution, it is necessary to comprehensively consider the combined effects of temperature and nutrient levels and conduct comparative analyses using multiple indicators such as algal biomass and diatom communities.
Algae are crucial primary producers in lake ecosystems, and their biomass and community structure can reflect water pollution and ecological status. As an important component of algae, the species composition characteristics of diatoms are also sensitive indicators for evaluating lake environmental quality. However, there is still a lack of systematic analysis regarding whether there are significant differences in the variation patterns and response mechanisms of algal biomass and diatom communities in lakes with different pollution levels. This study conducted seasonal investigations and comparative analyses in Lake Datun and Lake Yangzong, which have relatively high arsenic (As) pollution levels, and Lake Yilong, which is not affected by arsenic pollution, in Yunnan Province. The aim was to identify the main characteristics, driving factors, and key processes of algal changes 〖JP2〗under different arsenic pollution levels. Among the 55 surface water samples collected in this study, the concentration of water chlorophyll-a (Chl.a), which indicates algal biomass, was the highest in the eutrophic Lake Datun. Diatom compositions differed among the lakes and showed obvious seasonal fluctuations. Correlation analysis revealed a significant positive correlation between arsenic and Chl.aconcentrations in the lakes. This outcome indicates that phytoplankton are sensitive to arsenic stress in these lakes, and that the low arsenic levels exert a notable stimulating effect on algal growth. Meanwhile, arsenic was also significantly correlated with the main direction of diatom community changes. The results of variance decomposition analysis on algal data and environmental factors from the three lakes showed that the driving effect of the main environmental gradients on the succession of diatom community structure (PC1 index) was more significant than the fluctuation of Chl.a concentration (with average explained variances of 64.1% and 39.8%, respectively). The study results also revealed that the seasonal variation of water arsenic pollution is closely related to water temperature and lake depth type: increased water temperature promotes the chemical activity of arsenic and increases water arsenic concentration in shallow lakes, while in deep lakes, it limits the diffusion of sediment arsenic and the vertical migration of water arsenic through thermal stratification. In conclusion, the interactions between arsenic and factors such as water temperature, nutrients, and water depth under different pollution levels are significant, exerting important influences on the seasonal changes of algae and leading to large differences in the response intensities of different algal indicators. Therefore, for effective ecological assessment and restoration of lake arsenic pollution, it is necessary to comprehensively consider the combined effects of temperature and nutrient levels and conduct comparative analyses using multiple indicators such as algal biomass and diatom communities.
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2026,(5):000-000, DOI: 10.18307/2026.0545
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.
2026,(4):000-000, DOI: 10.18307/2026.0433
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.
2026,(4):000-000, DOI: 10.18307/2026.0442
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
2026,(4):000-000, DOI: 10.18307/2026.0426
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.
2026,(4):000-000, DOI: 10.18307/2026.0420
Available online: February 03, 2026
Abstract:
As a key sensitive area of water quality safety in Danjiangkou Reservoir, the bay has become the focus of water quality security work in the reservoir area. Based on the long-term monitoring data from 2015 to 2024, this study systematically analyzed the spatial and temporal distribution characteristics of water quality indicators and comprehensive nutritional status index TLI (∑) in the bay, and discussed the correlation between the nutritional status of the bay and the algal proliferation intensity and the correlation between the two and the water environmental factors. The results show that in the past ten years, The concentration changes of the main water quality indexes in the bays of Danjiangkou Reservoir show different characteristics. The average concentrations of TN and TP monitored in the past were 1.08 ~ 2.34 mg/L and 0.019 ~ 0.132 mg/L, respectively. The average value of TLI (∑) is between 31.05 ~ 51.26, and the nutritional status of the reservoir bay is generally mesotrophic. The results of trend analysis show that the TP concentration and TLI (∑) of the reservoir bay show a significant downward trend. There is a mutation point in TLI (∑) between May and October 2018, which is related to the long-term implementation of water quality security work in the reservoir area and upstream and the regulation of high water level conditions on the water quality of the reservoir bay. In terms of seasonal variation, the concentrations of water quality indicators in the bay were generally at a low level in winter. In the autumn flood season of some years, there were many extreme rainfall events, and the reservoir water level rose sharply. The concentrations of TN and CODMn in the bay increased significantly, but the concentration of TP decreased significantly. In terms of spatial distribution, the water quality of the bays in the reservoir tail areas of both the Hanjiang and Danjiang Reservoir areas is relatively poor, and the risk of eutrophication in local reservoir bays is high. The results of correlation analysis and variance decomposition showed that the TLI (∑) in the bay was mainly closely related to the pollution input process, and the growth of algae in the bay was more significantly affected by the physical and chemical indexes of the water body, especially WT. The results of this study can provide scientific basis and decision-making reference for the prevention and control of eutrophication and algal blooms in the Danjiangkou Reservoir Bay.
As a key sensitive area of water quality safety in Danjiangkou Reservoir, the bay has become the focus of water quality security work in the reservoir area. Based on the long-term monitoring data from 2015 to 2024, this study systematically analyzed the spatial and temporal distribution characteristics of water quality indicators and comprehensive nutritional status index TLI (∑) in the bay, and discussed the correlation between the nutritional status of the bay and the algal proliferation intensity and the correlation between the two and the water environmental factors. The results show that in the past ten years, The concentration changes of the main water quality indexes in the bays of Danjiangkou Reservoir show different characteristics. The average concentrations of TN and TP monitored in the past were 1.08 ~ 2.34 mg/L and 0.019 ~ 0.132 mg/L, respectively. The average value of TLI (∑) is between 31.05 ~ 51.26, and the nutritional status of the reservoir bay is generally mesotrophic. The results of trend analysis show that the TP concentration and TLI (∑) of the reservoir bay show a significant downward trend. There is a mutation point in TLI (∑) between May and October 2018, which is related to the long-term implementation of water quality security work in the reservoir area and upstream and the regulation of high water level conditions on the water quality of the reservoir bay. In terms of seasonal variation, the concentrations of water quality indicators in the bay were generally at a low level in winter. In the autumn flood season of some years, there were many extreme rainfall events, and the reservoir water level rose sharply. The concentrations of TN and CODMn in the bay increased significantly, but the concentration of TP decreased significantly. In terms of spatial distribution, the water quality of the bays in the reservoir tail areas of both the Hanjiang and Danjiang Reservoir areas is relatively poor, and the risk of eutrophication in local reservoir bays is high. The results of correlation analysis and variance decomposition showed that the TLI (∑) in the bay was mainly closely related to the pollution input process, and the growth of algae in the bay was more significantly affected by the physical and chemical indexes of the water body, especially WT. The results of this study can provide scientific basis and decision-making reference for the prevention and control of eutrophication and algal blooms in the Danjiangkou Reservoir Bay.
2026,(4):000-000, DOI: 10.18307/2026.0425
Available online: February 03, 2026
Abstract:
The coupling coordination between water sensitivity and industrial water environmental pollution stress in lake basins is important pathway for achieving sustainable watershed development. This study constructed an evaluation index system for both water sensitivity and industrial water environmental pollution stress in the watershed. The coupling coordination degree model, spatial Markov chain, and grey relational analysis were used to analyze the spatiotemporal evolution characteristics and driving factors of their coupling coordination in the Taihu Basin from 2007 to 2020. The results showed 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, the degree of 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 significant spatial differentiation. (2) The overall coupling coordination degree between water sensitivity and industrial water environmental pollution stress declined, exhibiting a “higher in the west and lower in the east” spatial distribution pattern, with characteristics of “club convergence” and a certain degree of spatial spillover effect. (3) The coupling coordination degree between water sensitivity and industrial water environmental pollution stress in the Taihu Basin was driven by five key factors, ranked in order of correlation as follows: technological investment level, industrial structure, population agglomeration degree, strength of environmental regulation, and socio-economic development level, with significant spatial variation in their effects. Therefore, this study suggests optimizing the spatial layout of productivity within the basin, implementing differentiated water environmental regulation policies, and improving the comprehensive watershed management, compensation, and monitoring and early warning system, thereby promoting the sustainable development of lake basins.
The coupling coordination between water sensitivity and industrial water environmental pollution stress in lake basins is important pathway for achieving sustainable watershed development. This study constructed an evaluation index system for both water sensitivity and industrial water environmental pollution stress in the watershed. The coupling coordination degree model, spatial Markov chain, and grey relational analysis were used to analyze the spatiotemporal evolution characteristics and driving factors of their coupling coordination in the Taihu Basin from 2007 to 2020. The results showed 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, the degree of 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 significant spatial differentiation. (2) The overall coupling coordination degree between water sensitivity and industrial water environmental pollution stress declined, exhibiting a “higher in the west and lower in the east” spatial distribution pattern, with characteristics of “club convergence” and a certain degree of spatial spillover effect. (3) The coupling coordination degree between water sensitivity and industrial water environmental pollution stress in the Taihu Basin was driven by five key factors, ranked in order of correlation as follows: technological investment level, industrial structure, population agglomeration degree, strength of environmental regulation, and socio-economic development level, with significant spatial variation in their effects. Therefore, this study suggests optimizing the spatial layout of productivity within the basin, implementing differentiated water environmental regulation policies, and improving the comprehensive watershed management, compensation, and monitoring and early warning system, thereby promoting the 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
2026,(4):000-000, DOI: 10.18307/2026.0437
Available online: February 03, 2026
Abstract:
Stream ecosystems are of significant ecological value due to their rich aquatic biodiversity and specificity, yet they are also highly vulnerable and urgently require more attention and protection. Zooplankton, as an important component of the aquatic food web, has long been overlooked in terms of its functional role in stream ecosystems. To investigate the role of zooplankton in stream ecosystems, this study focused on the headwaters of the Chishui River, a basin with minimal human impact and conducted a comparative analysis of the taxonomic and functional groups characteristics of zooplankton under two distinct hydrological conditions: the dry season (December) and the wet season (May). The relationships between these characteristics and water environmental factors were also examined. A total of 29 zooplankton species were identified. The number of species identified in the dry season (24 species) was twice that in the wet season (12 species). Compared to other water body types, the density of stream zooplankton was extremely low, ranging from 0.02 to 4.9 ind./L. Based on functional traits such as habitat preference, body size, and feeding habits, the taxonomic groups were classified into 11 functional groups. The occasional planktonic benthic scraper (SS), the small to medium-sized predator with swimming ability (SP), and the small filter-feeder (SCC) dominate the functional groups， and they all reflect functional adaptation strategies to turbulent habitats. This study report that the proportion of the benthic scraper group (SS) in the total functional groups in the stream can increase sharply from 17.7% in the dry season to 68.4% in the wet season, demonstrating a sensitive indicative characteristic in response to hydrological shifts. Furthermore, Mantel tests revealed that the composition of functional groups was significantly correlated with various environmental factors, including phytoplankton cell density, water temperature, pH, oxidation-reduction potential (ORP), total phosphorus (TP), and ammonium nitrogen (NH??-N), indicating that functional groups are more sensitive environmental indicators than taxonomic groups. The study demonstrates that the classification of functional groups can integrate species with similar ecological niches, thereby effectively compensating for the limitations of taxonomic groups in assessing the standing stock of stream zooplankton. This provides a new theoretical perspective for constructing diagnostic indicator systems for stream ecological health.
Stream ecosystems are of significant ecological value due to their rich aquatic biodiversity and specificity, yet they are also highly vulnerable and urgently require more attention and protection. Zooplankton, as an important component of the aquatic food web, has long been overlooked in terms of its functional role in stream ecosystems. To investigate the role of zooplankton in stream ecosystems, this study focused on the headwaters of the Chishui River, a basin with minimal human impact and conducted a comparative analysis of the taxonomic and functional groups characteristics of zooplankton under two distinct hydrological conditions: the dry season (December) and the wet season (May). The relationships between these characteristics and water environmental factors were also examined. A total of 29 zooplankton species were identified. The number of species identified in the dry season (24 species) was twice that in the wet season (12 species). Compared to other water body types, the density of stream zooplankton was extremely low, ranging from 0.02 to 4.9 ind./L. Based on functional traits such as habitat preference, body size, and feeding habits, the taxonomic groups were classified into 11 functional groups. The occasional planktonic benthic scraper (SS), the small to medium-sized predator with swimming ability (SP), and the small filter-feeder (SCC) dominate the functional groups， and they all reflect functional adaptation strategies to turbulent habitats. This study report that the proportion of the benthic scraper group (SS) in the total functional groups in the stream can increase sharply from 17.7% in the dry season to 68.4% in the wet season, demonstrating a sensitive indicative characteristic in response to hydrological shifts. Furthermore, Mantel tests revealed that the composition of functional groups was significantly correlated with various environmental factors, including phytoplankton cell density, water temperature, pH, oxidation-reduction potential (ORP), total phosphorus (TP), and ammonium nitrogen (NH??-N), indicating that functional groups are more sensitive environmental indicators than taxonomic groups. The study demonstrates that the classification of functional groups can integrate species with similar ecological niches, thereby effectively compensating for the limitations of taxonomic groups in assessing the standing stock of stream zooplankton. This provides 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
2026,(4):000-000, DOI: 10.18307/2026.0436
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.
2026,(4):000-000, DOI: 10.18307/2026.0422
Available online: February 02, 2026
Abstract:
Xiliang Lake, a representative macrophyte-dominated lake situated in the middle and lower reaches of the Yangtze River, provides critical insights into regional environmental management through the historical record of heavy metal pollution preserved in its sedimentary deposits. By integrating 21?Pb and 13?Cs 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 (RI), this study reconstructs the temporal evolution of heavy metal contamination and associated ecological risks in Xiliang Lake from 1858 to 2021. The findings reveal 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 by carbonate precipitation (indicated 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, of which Cd contributed up to 84%. Positive Matrix Factorization (PMF) analysis revealed that the contribution of natural sources decreased from 54% to 3% since 1858, whereas 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 (E?) for Cd surpassed the high-risk threshold (>80) in 1993, likely due to the combined influence of industrial pollutant inputs and the diminished capacity of ecological buffering resulting from vegetation degradation, which facilitated the remobilization of heavy metal species. This study elucidates a dual mechanism of "pollution buffering–risk transformation" in macrophyte-dominated lakes during phases of heavy metal accumulation and release, a process fundamentally distinct from that observed in algal-dominated lakes, thus providing a scientific foundation for differentiated management strategies and ecological restoration efforts in diverse lake ecosystems within the middle and lower reaches of the Yangtze River.
Xiliang Lake, a representative macrophyte-dominated lake situated in the middle and lower reaches of the Yangtze River, provides critical insights into regional environmental management through the historical record of heavy metal pollution preserved in its sedimentary deposits. By integrating 21?Pb and 13?Cs 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 (RI), this study reconstructs the temporal evolution of heavy metal contamination and associated ecological risks in Xiliang Lake from 1858 to 2021. The findings reveal 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 by carbonate precipitation (indicated 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, of which Cd contributed up to 84%. Positive Matrix Factorization (PMF) analysis revealed that the contribution of natural sources decreased from 54% to 3% since 1858, whereas 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 (E?) for Cd surpassed the high-risk threshold (>80) in 1993, likely due to the combined influence of industrial pollutant inputs and the diminished capacity of ecological buffering resulting from vegetation degradation, which facilitated the remobilization of heavy metal species. This study elucidates a dual mechanism of "pollution buffering–risk transformation" in macrophyte-dominated lakes during phases of heavy metal accumulation and release, a process fundamentally distinct from that observed in algal-dominated lakes, thus providing a scientific foundation for differentiated management strategies and ecological restoration efforts in diverse lake ecosystems within the middle and lower reaches of the Yangtze River.
2026,(4):000-000, DOI: 10.18307/2026.0414
Available online: January 30, 2026
Abstract:
Bacteria associated with colonial Microcystis phycoshpere and their interactions with Microcystis influence the growth and maintenance of the algae, thereby affecting the occurrence and disappearance of Microcystis blooms. Nutrients are one of the key factors influencing microbial growth, and Microcystis blooms are accompanied by fluctuations in nutrient levels. To investigate the effects of nutrient fluctuations on the composition of bacterial communities associated with Microcystis colonies, this study used a non-axenic strain of colonial Microcystis aeruginosa isolated from Lake Taihu as the research system. Based on multi-nutrient gradient culture experiments, the study examined the effects of different nutrient conditions, including nitrogen-deficient (ND), oligotrophic (O), mesotrophic (M), eutrophic (E), and hyper-eutrophic (BG-11) conditions, and analyzed the response of the associated bacterial communities to nutrient fluctuations during Microcystis growth. The results indicate that nutrient concentrations significantly influence the composition and diversity of the bacterial community. Under nitrogen-deficient, oligotrophic, and mesotrophic conditions, the community composition is more similar to each other, while under eutrophic and hyper-eutrophic conditions, differences increased. Additionally, high nitrogen and phosphorus concentrations reduce community richness and diversity. The core species at the phylum level are Proteobacteria, Bacteroidetes, and Armatimonadetes, with dominant orders including Rhizobiales, Caulobacterales, and Pseudomonadales. Core species exhibit differences under varying nutrient conditions: in the BG11 group, dominant bacterial communities include Actinobacteria and Cytophagales; in the O group, Bradyrhizobiaceae and Hyphomicrobiaceae are the primary distinct groups; The key groups in the ND group were Rhizobiales, etc.; the M group was dominated by Comamonadaceae, demonstrating the influence of nutrient salts on the composition of Microcystis epiphytic bacterial communities. Additionally, nutrient gradients alter community stability and interaction patterns. In eutrophic conditions, Microcystis exhibits stronger resistance and responsiveness, while bacterial cooperative relationships dominate in oligotrophic environments, with increased competition under eutrophic conditions. This study reveals the responses of algal-associated bacterial communities and algal-bacterial interactions to different nutrient gradient conditions, providing insights into the mechanisms underlying the maintenance of Microcystis blooms in water bodies with varying nutrient levels.
Bacteria associated with colonial Microcystis phycoshpere and their interactions with Microcystis influence the growth and maintenance of the algae, thereby affecting the occurrence and disappearance of Microcystis blooms. Nutrients are one of the key factors influencing microbial growth, and Microcystis blooms are accompanied by fluctuations in nutrient levels. To investigate the effects of nutrient fluctuations on the composition of bacterial communities associated with Microcystis colonies, this study used a non-axenic strain of colonial Microcystis aeruginosa isolated from Lake Taihu as the research system. Based on multi-nutrient gradient culture experiments, the study examined the effects of different nutrient conditions, including nitrogen-deficient (ND), oligotrophic (O), mesotrophic (M), eutrophic (E), and hyper-eutrophic (BG-11) conditions, and analyzed the response of the associated bacterial communities to nutrient fluctuations during Microcystis growth. The results indicate that nutrient concentrations significantly influence the composition and diversity of the bacterial community. Under nitrogen-deficient, oligotrophic, and mesotrophic conditions, the community composition is more similar to each other, while under eutrophic and hyper-eutrophic conditions, differences increased. Additionally, high nitrogen and phosphorus concentrations reduce community richness and diversity. The core species at the phylum level are Proteobacteria, Bacteroidetes, and Armatimonadetes, with dominant orders including Rhizobiales, Caulobacterales, and Pseudomonadales. Core species exhibit differences under varying nutrient conditions: in the BG11 group, dominant bacterial communities include Actinobacteria and Cytophagales; in the O group, Bradyrhizobiaceae and Hyphomicrobiaceae are the primary distinct groups; The key groups in the ND group were Rhizobiales, etc.; the M group was dominated by Comamonadaceae, demonstrating the influence of nutrient salts on the composition of Microcystis epiphytic bacterial communities. Additionally, nutrient gradients alter community stability and interaction patterns. In eutrophic conditions, Microcystis exhibits stronger resistance and responsiveness, while bacterial cooperative relationships dominate in oligotrophic environments, with increased competition under eutrophic conditions. This study reveals the responses of algal-associated bacterial communities and algal-bacterial interactions to different nutrient gradient conditions, providing insights into the mechanisms underlying the maintenance of Microcystis blooms in water bodies with varying nutrient levels.
2026,(4):000-000, DOI: 10.18307/2026.0424
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
2026,(4):000-000, DOI: 10.18307/2026.0435
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
2026,(4):000-000, DOI: 10.18307/2026.0423
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.
2026,(4):000-000, DOI: 10.18307/2026.0415
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.
2026,(4):000-000, DOI: 10.18307/2026.0430
Available online: January 21, 2026
Abstract:
The research on biological monitoring based on eDNA technology has witnessed rapid development and expansion in recent years, presenting a technological revolution trend that is partially replacing traditional field survey methods. In the vigorous expansion where so many researchers are competing to use eDNA technology for research and publishing papers, there are a series of risks that may undermine the foundation of these conclusions and the value of these papers. For instance, what object exactly does the eDNA monitoring result indicate? Is it appropriate to describe and analyze the eDNA monitoring results using traditional ecological concepts and methods applicable to individual survey data analysis? To explore this issue, the current manuscript took the applicability of the extended application of quantitative indicators from traditional community ecology in analyzing eDNA monitoring results as the starting point for its research. Four questions were analyzed. Firstly, what exactly does the relative abundance of DNA sequences of each detected species reflect in the eDNA monitoring results? Secondly, what exactly do the community quantitative indicators calculated based on the relative abundance of DNA sequences of each detected species indicate in the eDNA monitoring results? Thirdly, is it effective that using the relative abundance of DNA sequences of each detected species to replace the proportion of individual numbers or biomass in calculating community quantitative indicators? Fourthly, how to construct the concept system and terminology system for indicating and describing the community quantitative indicators calculated based on the detected species and the relative abundance of DNA sequences of each detected species reflect in the eDNA monitoring results? Then, it proposed three suggestions for the result description and interpretation in the biological monitoring and community analysis based on eDNA technology. The first, carefully describe the results of eDNA monitoring or investigation, and do not indiscreetly present them using the same methods for the results of traditional investigation and monitoring. The second, scientifically understand what the eDNA monitoring or investigation results indicate, and avoid ambiguity and confusion in the interpretation and discussion of the results. The third, get a growing consensus on this issue and construct the concept system and terminology system for indicating and describing the results of all research fields based on eDNA technology according to gradually explore and study. The current manuscript merely presents a preliminary exploration of the fundamental questions in the eDNA monitoring and analyzing, hoping to serve as a stimulus for further discussion.
The research on biological monitoring based on eDNA technology has witnessed rapid development and expansion in recent years, presenting a technological revolution trend that is partially replacing traditional field survey methods. In the vigorous expansion where so many researchers are competing to use eDNA technology for research and publishing papers, there are a series of risks that may undermine the foundation of these conclusions and the value of these papers. For instance, what object exactly does the eDNA monitoring result indicate? Is it appropriate to describe and analyze the eDNA monitoring results using traditional ecological concepts and methods applicable to individual survey data analysis? To explore this issue, the current manuscript took the applicability of the extended application of quantitative indicators from traditional community ecology in analyzing eDNA monitoring results as the starting point for its research. Four questions were analyzed. Firstly, what exactly does the relative abundance of DNA sequences of each detected species reflect in the eDNA monitoring results? Secondly, what exactly do the community quantitative indicators calculated based on the relative abundance of DNA sequences of each detected species indicate in the eDNA monitoring results? Thirdly, is it effective that using the relative abundance of DNA sequences of each detected species to replace the proportion of individual numbers or biomass in calculating community quantitative indicators? Fourthly, how to construct the concept system and terminology system for indicating and describing the community quantitative indicators calculated based on the detected species and the relative abundance of DNA sequences of each detected species reflect in the eDNA monitoring results? Then, it proposed three suggestions for the result description and interpretation in the biological monitoring and community analysis based on eDNA technology. The first, carefully describe the results of eDNA monitoring or investigation, and do not indiscreetly present them using the same methods for the results of traditional investigation and monitoring. The second, scientifically understand what the eDNA monitoring or investigation results indicate, and avoid ambiguity and confusion in the interpretation and discussion of the results. The third, get a growing consensus on this issue and construct the concept system and terminology system for indicating and describing the results of all research fields based on eDNA technology according to gradually explore and study. The current manuscript merely presents a preliminary exploration of the fundamental questions in the eDNA monitoring and analyzing, hoping to serve as a stimulus for further discussion.
Wangjin, Zhuang xinfeng, Tang caihong, Cai yongjiu, Gong zhijun, Zhang shanghong, Kong xiangzhen, Deng jianming
2026,(4):000-000, DOI: 10.18307/2026.0431
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.
2026,(4):000-000, DOI: 10.18307/2026.0421
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.
2026,(4):000-000, DOI: 10.18307/2026.0452
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.
2026,(4):000-000, DOI: 10.18307/2026.0443
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.
2026,(4):000-000, DOI: 10.18307/2026.0454
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.
2026,(4):000-000, DOI: 10.18307/2026.0453
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.
2026,(3):000-000, DOI: 10.18307/2026.0318
Available online: January 09, 2026
Abstract:
The Water Diversion from Yangtze River to Lake Taihu Project (WDYT) is an important water transfer project implemented to improve the water environment of Lake Taihu. However, its impact on phosphorus levels in the lake—particularly the contribution of bioavailable phosphorus and its relationship with algal bloom risk—remains unclear. This study aims to analyze the extent of the project"s influence on phosphorus in Lake Taihu, its contribution, and its association with algal bloom risk. The Wangyu River diversion channel and the receiving Gonghu Bay of Lake Taihu were selected as the key study areas, with the central zone of the lake serving as a reference for comparing the effects of water diversion. Field investigations were conducted during dry seasons (autumn and winter) from 2018 to 2022. Monitoring included concentrations of total phosphorus (TP), total dissolved phosphorus (DTP), soluble reactive phosphorus (SRP), and other physicochemical environmental factors such as chlorophyll-a (Chl.a). Particulate phosphorus (PP) and dissolved organic phosphorus (DOP) were estimated, and statistical analyses were applied to assess the influence of water diversion on phosphorus in river and lake waters and its correlation with algal risk. The results showed that during the autumn diversion period, phosphorus concentrations in the Wangyu River decreased along the flow path from the Yangtze River to the lake inlet, while in winter, they exhibited a fluctuated with an overall increasing trend. From Gonghu Bay toward the central lake zone, the concentrations of the four phosphorus forms (TP、DTP、SRP、DOP) displayed fluctuating but generally increasing trends during both diversion and non-diversion periods in autumn and winter. During diversion periods, the average proportions of PP in Gonghu Bay were 47.0% in autumn and 31.5% in winter, higher than those during non-diversion periods in the same seasons (37.33% and 20.16%, respectively). However, the phosphorus concentrations in the inflow water of the Wangyu River were generally comparable to or even lower than those in the central lake zone. Dry-season water diversion did not significantly influence phosphorus levels in Gonghu Bay, particularly in terms of dissolved bioavailable phosphorus. In autumn, Chl.a in Gonghu Bay was correlated with water temperature and turbidity, while in winter, it showed significant correlations with DO and pH. No significant correlation was found between Chl.a and phosphorus concentrations in Gonghu Bay. With the operation of the western control project on the Wangyu River, dry-season water diversion under the WDYT framework does not significantly increase the phosphorus load in the receiving lake areas, especially dissolved bioavailable phosphorus that can be directly utilized by phytoplankton. These findings indicate that phytoplankton growth in Gonghu Bay during the dry season is not sensitive to phosphorus concentrations in the water. The diverted phosphorus exhibits limited direct ecological effects in the short term. Nevertheless, its long-term accumulation and potential implications for the ’lacustrine algal blooms need further study.
The Water Diversion from Yangtze River to Lake Taihu Project (WDYT) is an important water transfer project implemented to improve the water environment of Lake Taihu. However, its impact on phosphorus levels in the lake—particularly the contribution of bioavailable phosphorus and its relationship with algal bloom risk—remains unclear. This study aims to analyze the extent of the project"s influence on phosphorus in Lake Taihu, its contribution, and its association with algal bloom risk. The Wangyu River diversion channel and the receiving Gonghu Bay of Lake Taihu were selected as the key study areas, with the central zone of the lake serving as a reference for comparing the effects of water diversion. Field investigations were conducted during dry seasons (autumn and winter) from 2018 to 2022. Monitoring included concentrations of total phosphorus (TP), total dissolved phosphorus (DTP), soluble reactive phosphorus (SRP), and other physicochemical environmental factors such as chlorophyll-a (Chl.a). Particulate phosphorus (PP) and dissolved organic phosphorus (DOP) were estimated, and statistical analyses were applied to assess the influence of water diversion on phosphorus in river and lake waters and its correlation with algal risk. The results showed that during the autumn diversion period, phosphorus concentrations in the Wangyu River decreased along the flow path from the Yangtze River to the lake inlet, while in winter, they exhibited a fluctuated with an overall increasing trend. From Gonghu Bay toward the central lake zone, the concentrations of the four phosphorus forms (TP、DTP、SRP、DOP) displayed fluctuating but generally increasing trends during both diversion and non-diversion periods in autumn and winter. During diversion periods, the average proportions of PP in Gonghu Bay were 47.0% in autumn and 31.5% in winter, higher than those during non-diversion periods in the same seasons (37.33% and 20.16%, respectively). However, the phosphorus concentrations in the inflow water of the Wangyu River were generally comparable to or even lower than those in the central lake zone. Dry-season water diversion did not significantly influence phosphorus levels in Gonghu Bay, particularly in terms of dissolved bioavailable phosphorus. In autumn, Chl.a in Gonghu Bay was correlated with water temperature and turbidity, while in winter, it showed significant correlations with DO and pH. No significant correlation was found between Chl.a and phosphorus concentrations in Gonghu Bay. With the operation of the western control project on the Wangyu River, dry-season water diversion under the WDYT framework does not significantly increase the phosphorus load in the receiving lake areas, especially dissolved bioavailable phosphorus that can be directly utilized by phytoplankton. These findings indicate that phytoplankton growth in Gonghu Bay during the dry season is not sensitive to phosphorus concentrations in the water. The diverted phosphorus exhibits limited direct ecological effects in the short term. Nevertheless, its long-term accumulation and potential implications for the ’lacustrine algal blooms need further study.
2026,(4):000-000, DOI: 10.18307/2026.0441
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
2026,(4):000-000, DOI: 10.18307/2026.0412
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.
2026,(4):000-000, DOI: 10.18307/2026.0445
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.
2026,(4):000-000, DOI: 10.18307/2026.0411
Available online: January 04, 2026
Abstract:
The transport process of sediment particulates and particulate phosphorus (PP) in shallow lakes is crucial for sediment deposition and water quality evolution. Aiming at the unclear issue regarding the transport mechanism of particulates and particulate phosphorus in Lake Taihu and their contribution to sediment deposition, this study investigated the overall balance, transport characteristics, and deposition patterns of suspended solids (SS) and particulate phosphorus entering and exiting Lake Taihu. The research was conducted through a one-year monitoring of inflow and outflow rivers, combined with a one-month whole-lake sampling and particle size classification analysis, and the application of the flux balance method. The results indicated that the in-lake sediment accumulation of particulates in Lake Taihu was significant, and the retention of phosphorus with particulates was prominent. In 2021, the net inflow of SS into Lake Taihu was approximately 400,000 tons, corresponding to a sediment volume of about 550,000 m3, with a deposition rate of 0.35 millimeters per year. During the same period, the net retention of PP was 989 tons, and approximately 73% of the inflowing PP entered Lake Taihu along with particulates, which revealed that particulate sedimentation was identified as the main pathway for phosphorus accumulation. There were significant differences in the particle size of particulates and the occurrence forms of phosphorus between the inflow and outflow of Lake Taihu. The inflowing particulates were mainly 20-50 μm in size, while the outflowing ones were mainly 0.45-10 μm. Moreover, the particulates of 10-20 μm carried more than 80% of PP. The hydrodynamic process in the lake had a significant impact on the spatial distribution of particulates and PP. The particulates in Lake Taihu showed a distribution pattern of "high in the west and low in the east", while particulate phosphorus exhibited a characteristic of "high in the northwest and low in the southeast.
The transport process of sediment particulates and particulate phosphorus (PP) in shallow lakes is crucial for sediment deposition and water quality evolution. Aiming at the unclear issue regarding the transport mechanism of particulates and particulate phosphorus in Lake Taihu and their contribution to sediment deposition, this study investigated the overall balance, transport characteristics, and deposition patterns of suspended solids (SS) and particulate phosphorus entering and exiting Lake Taihu. The research was conducted through a one-year monitoring of inflow and outflow rivers, combined with a one-month whole-lake sampling and particle size classification analysis, and the application of the flux balance method. The results indicated that the in-lake sediment accumulation of particulates in Lake Taihu was significant, and the retention of phosphorus with particulates was prominent. In 2021, the net inflow of SS into Lake Taihu was approximately 400,000 tons, corresponding to a sediment volume of about 550,000 m3, with a deposition rate of 0.35 millimeters per year. During the same period, the net retention of PP was 989 tons, and approximately 73% of the inflowing PP entered Lake Taihu along with particulates, which revealed that particulate sedimentation was identified as the main pathway for phosphorus accumulation. There were significant differences in the particle size of particulates and the occurrence forms of phosphorus between the inflow and outflow of Lake Taihu. The inflowing particulates were mainly 20-50 μm in size, while the outflowing ones were mainly 0.45-10 μm. Moreover, the particulates of 10-20 μm carried more than 80% of PP. The hydrodynamic process in the lake had a significant impact on the spatial distribution of particulates and PP. The particulates in Lake Taihu showed a distribution pattern of "high in the west and low in the east", while particulate phosphorus exhibited a characteristic of "high in the northwest and low in the southeast.
Xi Ying, Long Jingzhong, Yu Shuilian, Chen Jingyi, Li Kun, Wang Siting, Xu Tao, Huang Yingping, Lv Yuanfei
2026,(5):000-000, DOI: 10.18307/2026.0524
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.
2026,(4):000-000, DOI: 10.18307/2026.0434
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.
2026,(4):000-000, DOI: 10.18307/2026.0450
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.
2026,(4):000-000, DOI: 10.18307/2026.0413
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.
2026,(4):000-000, DOI: 10.18307/2026.0444
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.
2026,(3):000-000, DOI: 10.18307/2026.0344
Available online: November 27, 2025
Abstract:
Groundwater dynamics processes in floodplains affect the transfer and exchange of materials, energy, and information between hydrological environment systems and are important forcings for maintaining the integrity of the floodplain wetland ecosystem. This study focuses on the groundwater system in the floodplain area of Poyang Lake in the middle reaches of the Yangtze River. Based on spatial zoning of hydrogeological parameters and vertical layering characterization of aquifers, a qusi-3D groundwater flow numerical model of the Poyang Lake floodplain area was constructed by using FEFLOW. The study quantitatively analyzed the spatiotemporal response characteristics of groundwater dynamics under different hydrological stages in normal years, revealing the relative contribution components of the equilibrium factors in the floodplain"s groundwater system and the dynamic changes in groundwater storage throughout the year. The research shows that the model exhibits good predictive ability in simulating groundwater level changes over time and space. The determination coefficient of groundwater level simulation during the calibration period (2018) and validation period (2019-2020) was greater than 0.85, with a Nash efficiency coefficient greater than 0.80, and the groundwater level deviation was generally less than 0.45 m. Influenced by the annual dynamic water level changes in Poyang Lake, the groundwater level in the floodplain exhibits distinct seasonal fluctuations, with differences of about 2-3 m between the wet and dry seasons. Due to the heterogeneous topography and geomorphology of the entire lake basin, the groundwater level in the floodplain shows a spatially differentiated distribution pattern, with higher levels in the south, lower levels in the north, and higher levels in the east and lower levels in the west. Under the combined effect of lake water levels and topography, the groundwater flow velocity in most areas of the floodplain is less than 0.1 m/d. However, the groundwater flow velocity in some areas can reach up to 0.3 m/d during the rising water and wet seasons. The main flow direction of the groundwater is from the east, near the main lake area, toward the west floodplain, with this flow trend being particularly obvious during high water levels. The water budget analysis shows that precipitation infiltration, evaporation, and the water exchange between the aquifer and the lake area are the main factors affecting floodplain groundwater budget. Precipitation infiltration accounts for about 64%-65% of the total recharge volume, while lake water recharge accounts for about 29%-30%, and the infiltration recharge capacity of the seasonal lake group is relatively weak, contributing only 2% of the total recharge. Evaporation accounts for about 70%-73% of the total discharge volume, and the aquifer"s discharge to the lake accounts for about 23%-26% of the total recharge. In the spring and summer, the groundwater system in the Poyang Lake floodplain mainly shows positive balance (i.e., receiving water), while in the autumn and winter, it mainly shows negative balance (i.e., discharging water). The results of this study can provide a critical scientific basis and decision-making support for addressing seasonal droughts in Poyang Lake, ensuring regional water supply security, and sustaining wetland ecosystem.
Groundwater dynamics processes in floodplains affect the transfer and exchange of materials, energy, and information between hydrological environment systems and are important forcings for maintaining the integrity of the floodplain wetland ecosystem. This study focuses on the groundwater system in the floodplain area of Poyang Lake in the middle reaches of the Yangtze River. Based on spatial zoning of hydrogeological parameters and vertical layering characterization of aquifers, a qusi-3D groundwater flow numerical model of the Poyang Lake floodplain area was constructed by using FEFLOW. The study quantitatively analyzed the spatiotemporal response characteristics of groundwater dynamics under different hydrological stages in normal years, revealing the relative contribution components of the equilibrium factors in the floodplain"s groundwater system and the dynamic changes in groundwater storage throughout the year. The research shows that the model exhibits good predictive ability in simulating groundwater level changes over time and space. The determination coefficient of groundwater level simulation during the calibration period (2018) and validation period (2019-2020) was greater than 0.85, with a Nash efficiency coefficient greater than 0.80, and the groundwater level deviation was generally less than 0.45 m. Influenced by the annual dynamic water level changes in Poyang Lake, the groundwater level in the floodplain exhibits distinct seasonal fluctuations, with differences of about 2-3 m between the wet and dry seasons. Due to the heterogeneous topography and geomorphology of the entire lake basin, the groundwater level in the floodplain shows a spatially differentiated distribution pattern, with higher levels in the south, lower levels in the north, and higher levels in the east and lower levels in the west. Under the combined effect of lake water levels and topography, the groundwater flow velocity in most areas of the floodplain is less than 0.1 m/d. However, the groundwater flow velocity in some areas can reach up to 0.3 m/d during the rising water and wet seasons. The main flow direction of the groundwater is from the east, near the main lake area, toward the west floodplain, with this flow trend being particularly obvious during high water levels. The water budget analysis shows that precipitation infiltration, evaporation, and the water exchange between the aquifer and the lake area are the main factors affecting floodplain groundwater budget. Precipitation infiltration accounts for about 64%-65% of the total recharge volume, while lake water recharge accounts for about 29%-30%, and the infiltration recharge capacity of the seasonal lake group is relatively weak, contributing only 2% of the total recharge. Evaporation accounts for about 70%-73% of the total discharge volume, and the aquifer"s discharge to the lake accounts for about 23%-26% of the total recharge. In the spring and summer, the groundwater system in the Poyang Lake floodplain mainly shows positive balance (i.e., receiving water), while in the autumn and winter, it mainly shows negative balance (i.e., discharging water). The results of this study can provide a critical scientific basis and decision-making support for addressing seasonal droughts in Poyang Lake, ensuring regional water supply security, and sustaining wetland ecosystem.
2026,(3):000-000, DOI: 10.18307/2026.0313
Available online: November 27, 2025
Abstract:
Mesotrophic lakes and reservoirs, as critical sources of drinking water, have unclear mechanisms for the formation of its occasional algal blooms and the dynamics of nutrient limitations. This study took the Reservoir Duihekou in Zhejiang as a research object and revealed the fluctuation in algal growth rates and the dynamic coupling relationship between growth rates and nutrient quotas through four years of in situ monitoring. The results showed that during the diatom dominance phase (December to April, DIA), the in situ algal growth rate (μ) fluctuated significantly, ranging from -1.10 to 2.76 d-1, while during the cyanobacteria dominance phase (July to August, CYA), the range is -0.43 to 0.81 d-1, higher than in eutrophic waters, indicating the rapid proliferation potential of algae in mesotrophic systems. Algal growth rates during DIA were mainly dominated by nitrogen cell quotas (CQN, P<0.001). This might be attributed to the inhibitory effects of light limitation and low temperatures on chlorophyll synthesis and nitrogen assimilation efficiency. Consequently, if the gradual increase in temperature and light intensity during spring coincided with an elevated nitrogen cell quota in algae, it could potentially trigger a diatom bloom. While the growth rates during CYA were synergistically regulated by phosphorus cell quotas (CQP) and phosphorus environment quotas (EQP, P<0.001). It suggested maintaining total phosphorus (TP) below 22 μg/L (95% CI: 15–32 μg/L) could effectively control cyanobacteria blooms (Chl.a >10 μg/L). This study innovatively introduced dynamic cellular quotas to analyze algal growth mechanisms, resolving traditional reliance on relationships between environmental nutrient concentrations and algal biomass or nitrogen-to-phosphorus ratios to judge the nutrient limitation types. This provides a new theoretical framework for water quality management and bloom warning in mesotrophic lakes and reservoirs.
Mesotrophic lakes and reservoirs, as critical sources of drinking water, have unclear mechanisms for the formation of its occasional algal blooms and the dynamics of nutrient limitations. This study took the Reservoir Duihekou in Zhejiang as a research object and revealed the fluctuation in algal growth rates and the dynamic coupling relationship between growth rates and nutrient quotas through four years of in situ monitoring. The results showed that during the diatom dominance phase (December to April, DIA), the in situ algal growth rate (μ) fluctuated significantly, ranging from -1.10 to 2.76 d-1, while during the cyanobacteria dominance phase (July to August, CYA), the range is -0.43 to 0.81 d-1, higher than in eutrophic waters, indicating the rapid proliferation potential of algae in mesotrophic systems. Algal growth rates during DIA were mainly dominated by nitrogen cell quotas (CQN, P<0.001). This might be attributed to the inhibitory effects of light limitation and low temperatures on chlorophyll synthesis and nitrogen assimilation efficiency. Consequently, if the gradual increase in temperature and light intensity during spring coincided with an elevated nitrogen cell quota in algae, it could potentially trigger a diatom bloom. While the growth rates during CYA were synergistically regulated by phosphorus cell quotas (CQP) and phosphorus environment quotas (EQP, P<0.001). It suggested maintaining total phosphorus (TP) below 22 μg/L (95% CI: 15–32 μg/L) could effectively control cyanobacteria blooms (Chl.a >10 μg/L). This study innovatively introduced dynamic cellular quotas to analyze algal growth mechanisms, resolving traditional reliance on relationships between environmental nutrient concentrations and algal biomass or nitrogen-to-phosphorus ratios to judge the nutrient limitation types. This provides a new theoretical framework for water quality management and bloom warning in mesotrophic lakes and reservoirs.
2026,(4):000-000, DOI: 10.18307/2026.0451
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.
2026,(3):000-000, DOI: 10.18307/2026.0335
Available online: November 26, 2025
Abstract:
Poyang Lake is one of the most important wintering habitats for waterbirds along the East Asian–Australasian Flyway. Carex spp., the dominant plant in Poyang Lake wetlands, is the main food source for overwintering geese, and its growth directly affects their foraging efficiency and energy intake. In recent years, hydrological regimes of Poyang Lake have been significantly altered by hydrological engineering and frequent extreme weather, which has disrupted the growth dynamics of Carex, leading to a mismatch with the migratory timing of overwintering geese. Mowing, a common management practice in grassland ecosystems, can stimulate plant regeneration and regulate growth rhythms, partially alleviating food resource mismatches and improving foraging conditions for geese. This study focused on Carex in the floodplains of Poyang Lake. In a field experiment, we selected exposed Carex during autumn and winter and applied different mowing frequencies across areas with varying soil moisture levels, with long-term management and monitoring. Results showed that increasing soil moisture significantly promoted plant height and aboveground biomass, while belowground biomass peaked only under low soil moisture 15 days after mowing. Multiple mowing significantly suppressed plant height and aboveground biomass and weakened the promoting effect of soil moisture, causing growth indicators across different moisture gradients to converge. Both soil moisture gradient and mowing frequency significantly affect plant height, aboveground biomass, and belowground biomass of Carex, with optimal growth observed under high soil moisture (≥ 33.79%) and low-intensity mowing (≤ 4 times). The results provide quantifiable parameters for water regulation and mowing frequency to guide the management of wintering waterbird habitats in the Poyang Lake wetlands.
Poyang Lake is one of the most important wintering habitats for waterbirds along the East Asian–Australasian Flyway. Carex spp., the dominant plant in Poyang Lake wetlands, is the main food source for overwintering geese, and its growth directly affects their foraging efficiency and energy intake. In recent years, hydrological regimes of Poyang Lake have been significantly altered by hydrological engineering and frequent extreme weather, which has disrupted the growth dynamics of Carex, leading to a mismatch with the migratory timing of overwintering geese. Mowing, a common management practice in grassland ecosystems, can stimulate plant regeneration and regulate growth rhythms, partially alleviating food resource mismatches and improving foraging conditions for geese. This study focused on Carex in the floodplains of Poyang Lake. In a field experiment, we selected exposed Carex during autumn and winter and applied different mowing frequencies across areas with varying soil moisture levels, with long-term management and monitoring. Results showed that increasing soil moisture significantly promoted plant height and aboveground biomass, while belowground biomass peaked only under low soil moisture 15 days after mowing. Multiple mowing significantly suppressed plant height and aboveground biomass and weakened the promoting effect of soil moisture, causing growth indicators across different moisture gradients to converge. Both soil moisture gradient and mowing frequency significantly affect plant height, aboveground biomass, and belowground biomass of Carex, with optimal growth observed under high soil moisture (≥ 33.79%) and low-intensity mowing (≤ 4 times). The results provide quantifiable parameters for water regulation and mowing frequency to guide the management of wintering waterbird habitats in the Poyang Lake wetlands.
2026,(3):000-000, DOI: 10.18307/2026.0351
Available online: November 26, 2025
Abstract:
Northeast China is a mid- to high-latitude region with significant lake distribution and high sensitivity to climate change. Its unique seasonal lake ice phenology changes have a substantial impact on the lake ecosystem. However, there is a lack of long-term lake ice phenology data in Northeast China, making it difficult to identify the characteristics of lake ice phenology changes. To this end, this study employed the XGBoost-SHAP machine learning model to construct a lake ice phenology dataset for key lakes in Northeast China (Hulun, Lianhuan, Chagan, Xingkai, and Wolong Lakes) from 1981 to 2023, and conducted a quantitative analysis of the characteristics of lake ice phenology changes and their driving factors. The results show that (1) the XGBoost-based lake ice phenology prediction model achieves high accuracy. Specifically, the coefficient of determination (R2) for predicting freeze-up data is 0.97, with an average absolute percentage error of 0.5%. For predicting break-up data, the R2 value is also 0.97, but the average absolute percentage error is slightly higher at 1.9%. (2) Lake ice phenology exhibits the characteristics and trends of delayed freeze-up data, advanced break-up data, and shortened ice cover duration. At high-latitude Hulun Lake, freeze-up is delayed by 0.18 d/a, break-up advances by 0.37 d/a, and ice cover duration is shortened by 0.55 d/a. In contrast, at the relatively lower-latitude Wolong Lake, freeze-up is delayed by 0.13 d/a, break-up advances by 0.20 d/a, and ice cover duration is reduced by 0.33 d/a. (3) The primary driver of lake ice phenology changes is air temperature, contributing 40.5% and 31.2% to freeze-up and break-up data, respectively. The study"s findings enhance our understanding of the response mechanisms of lake ice phenology in cold regions to global climate change and provide scientific support for lake water environment protection and water ecology management.
Northeast China is a mid- to high-latitude region with significant lake distribution and high sensitivity to climate change. Its unique seasonal lake ice phenology changes have a substantial impact on the lake ecosystem. However, there is a lack of long-term lake ice phenology data in Northeast China, making it difficult to identify the characteristics of lake ice phenology changes. To this end, this study employed the XGBoost-SHAP machine learning model to construct a lake ice phenology dataset for key lakes in Northeast China (Hulun, Lianhuan, Chagan, Xingkai, and Wolong Lakes) from 1981 to 2023, and conducted a quantitative analysis of the characteristics of lake ice phenology changes and their driving factors. The results show that (1) the XGBoost-based lake ice phenology prediction model achieves high accuracy. Specifically, the coefficient of determination (R2) for predicting freeze-up data is 0.97, with an average absolute percentage error of 0.5%. For predicting break-up data, the R2 value is also 0.97, but the average absolute percentage error is slightly higher at 1.9%. (2) Lake ice phenology exhibits the characteristics and trends of delayed freeze-up data, advanced break-up data, and shortened ice cover duration. At high-latitude Hulun Lake, freeze-up is delayed by 0.18 d/a, break-up advances by 0.37 d/a, and ice cover duration is shortened by 0.55 d/a. In contrast, at the relatively lower-latitude Wolong Lake, freeze-up is delayed by 0.13 d/a, break-up advances by 0.20 d/a, and ice cover duration is reduced by 0.33 d/a. (3) The primary driver of lake ice phenology changes is air temperature, contributing 40.5% and 31.2% to freeze-up and break-up data, respectively. The study"s findings enhance our understanding of the response mechanisms of lake ice phenology in cold regions to global climate change and provide scientific support for lake water environment protection and water ecology management.
2026,(3):000-000, DOI: 10.18307/2026.0328
Available online: November 24, 2025
Abstract:
In order to investigate the composition and spatial distribution of PFAS in surface water environment, this study collected and analyzed six common PFAS pollutants in 30 wetland water samples, performed source apportionment based on the PMF model, and assessed their potential water ecological risk via risk quotient (RQ) evaluation. The results showed that PFOA, as one of the most predominant PFAS pollutants in the region, was detected in all samples (100% detection rate), with a maximum concentration of 461.32 ng·L?1. Detection rates for PFOS, PFNA, PFBS, PFHpA, and PFHxS ranged from 30.0% to 96.67%, and the total concentration of PFAS was higher in the southern bank of the Yellow River than in the northern bank. PMF source apportionment identified three main contamination sources, including production and industrial wastewater discharge of fire-fighting foam (22.41%), degradation of precursor compounds (24.00%), production and industrial wastewater discharge of fluorinated compounds (53.59%). Risk quotient assessment indicated that PFOA and PFNA posed moderate and low ecological risk to algae, respectively, while PFOA presented low risk level to daphnia, shrimp, and fish. Fluorochemical industry production and wastewater discharge source and PFOA constituted the predominant ecological risk in the study area, requiring attention to long-term exposure risk and priority control. This research can provide critical scientific support for source control and risk assessment of PFAS in the Yellow River Delta.
In order to investigate the composition and spatial distribution of PFAS in surface water environment, this study collected and analyzed six common PFAS pollutants in 30 wetland water samples, performed source apportionment based on the PMF model, and assessed their potential water ecological risk via risk quotient (RQ) evaluation. The results showed that PFOA, as one of the most predominant PFAS pollutants in the region, was detected in all samples (100% detection rate), with a maximum concentration of 461.32 ng·L?1. Detection rates for PFOS, PFNA, PFBS, PFHpA, and PFHxS ranged from 30.0% to 96.67%, and the total concentration of PFAS was higher in the southern bank of the Yellow River than in the northern bank. PMF source apportionment identified three main contamination sources, including production and industrial wastewater discharge of fire-fighting foam (22.41%), degradation of precursor compounds (24.00%), production and industrial wastewater discharge of fluorinated compounds (53.59%). Risk quotient assessment indicated that PFOA and PFNA posed moderate and low ecological risk to algae, respectively, while PFOA presented low risk level to daphnia, shrimp, and fish. Fluorochemical industry production and wastewater discharge source and PFOA constituted the predominant ecological risk in the study area, requiring attention to long-term exposure risk and priority control. This research can provide critical scientific support for source control and risk assessment of PFAS in the Yellow River Delta.
2026,(3):000-000, DOI: 10.18307/2026.0337
Available online: November 24, 2025
Abstract:
Batrachospermaceae is a family of freshwater red algae with filamentous frond, and many members of which are endangered due to the scarcity of their populations. This study uses a range of analytical methods, including one-way ANOVA, principal component analysis, random forest modeling and multiple linear regression, to examine the relationship between environmental data of Batrachospermaceae and compare it with that of Zygnemataceae and Cladophraceae (green algae), which are both large filamentous freshwater algae, furthermore, to analyze the endangered mechanism of Batrachospermaceae. The results demonstrated that: (1) The distribution ranges of WT, pH, DO, SPC, TDS, SAL, NH4+-N, TP and COD in the environmental data of Batrachospermaceae were smaller than those of Zygnemataceae and Cladophraceae. This finding suggests that Batrachospermaceae exhibits limited adaptability to the environment and strict habitat requirements. (2) WT, TP, TN and COD are all important environmental factors affecting the distribution of Batrachospermaceae. In comparison to Zygnemataceae and Cladophraceae, Batrachospermaceae has more important environmental factors, which suggests that Batrachospermaceae is influenced and constrained by a greater number of factors during its growth process, causes of the endangered status of this species. The findings provide a scientific foundation for the conservation and restoration of Batrachospermaceae.
Batrachospermaceae is a family of freshwater red algae with filamentous frond, and many members of which are endangered due to the scarcity of their populations. This study uses a range of analytical methods, including one-way ANOVA, principal component analysis, random forest modeling and multiple linear regression, to examine the relationship between environmental data of Batrachospermaceae and compare it with that of Zygnemataceae and Cladophraceae (green algae), which are both large filamentous freshwater algae, furthermore, to analyze the endangered mechanism of Batrachospermaceae. The results demonstrated that: (1) The distribution ranges of WT, pH, DO, SPC, TDS, SAL, NH4+-N, TP and COD in the environmental data of Batrachospermaceae were smaller than those of Zygnemataceae and Cladophraceae. This finding suggests that Batrachospermaceae exhibits limited adaptability to the environment and strict habitat requirements. (2) WT, TP, TN and COD are all important environmental factors affecting the distribution of Batrachospermaceae. In comparison to Zygnemataceae and Cladophraceae, Batrachospermaceae has more important environmental factors, which suggests that Batrachospermaceae is influenced and constrained by a greater number of factors during its growth process, causes of the endangered status of this species. The findings provide a scientific foundation for the conservation and restoration of Batrachospermaceae.
2026,(3):000-000, DOI: 10.18307/2026.0333
Available online: November 24, 2025
Abstract:
The aim of this study was try to answer whether there are significant differences in vegetation characteristics between different elevations and land use types in the the water level fluctuation zone (WLFZ) of Danjiangkou Reservoir. From July to August 2024, samples were collected from a total of 45 sites along three WLFZ elevation gradients (155~160, 160~165, and 165~170m) . The results showed that there were 55 families, 140 genera, and 170 species of large vascular plants in the WLZ, with the highest number in the Asteraceae family, followed by the Poaceae, Fabaceae, and Euphorbiaceae families. The plant community was mainly composed of herbaceous plants, with the largest number of annual herbaceous plant species (46.47%), followed by perennial herbaceous plants (32.35%) and woody plants (shrubs, vines, and trees) (21.18%). There were significant differences in the dominant species of plants in the WLZ at different elevation zones. The plants with the highest dominance in the 155~160, 160~165, and 165~170m areas was Cynodon dactylon, Digitaria sanguinalis and Artemisia annua, respectively. The mean plant biomass was (822.4±709.4)g·m-2, and the mean Shannon Wiener diversity index was (1.67±0.45). There was no significant difference in vegetation coverage, height, biomass, and diversity among different elevation zones. As the elevation increased, the vegetation height showed an increasing trend. There were significant differences in vegetation coverage, biomass, and diversity among different land use types. The vegetation coverage in grassland was significantly higher than that of forest land (understory herbaceous plants) and water conservancy facility land, while plant biomass in grassland and cultivated land was significantly higher than that of forest land (understory herbaceous plants) and water conservancy facility land. The plant diversity index in grassland, forest land(understory herbaceous plants), and water conservancy facilities land was significantly higher than that of cultivated land. The reproductive mode and seed dispersal ability of plants in the WLFZ were the internal factors affecting the distribution pattern of vegetation, while human activities such as reservoir operation and land use types were also the main driving factors.
The aim of this study was try to answer whether there are significant differences in vegetation characteristics between different elevations and land use types in the the water level fluctuation zone (WLFZ) of Danjiangkou Reservoir. From July to August 2024, samples were collected from a total of 45 sites along three WLFZ elevation gradients (155~160, 160~165, and 165~170m) . The results showed that there were 55 families, 140 genera, and 170 species of large vascular plants in the WLZ, with the highest number in the Asteraceae family, followed by the Poaceae, Fabaceae, and Euphorbiaceae families. The plant community was mainly composed of herbaceous plants, with the largest number of annual herbaceous plant species (46.47%), followed by perennial herbaceous plants (32.35%) and woody plants (shrubs, vines, and trees) (21.18%). There were significant differences in the dominant species of plants in the WLZ at different elevation zones. The plants with the highest dominance in the 155~160, 160~165, and 165~170m areas was Cynodon dactylon, Digitaria sanguinalis and Artemisia annua, respectively. The mean plant biomass was (822.4±709.4)g·m-2, and the mean Shannon Wiener diversity index was (1.67±0.45). There was no significant difference in vegetation coverage, height, biomass, and diversity among different elevation zones. As the elevation increased, the vegetation height showed an increasing trend. There were significant differences in vegetation coverage, biomass, and diversity among different land use types. The vegetation coverage in grassland was significantly higher than that of forest land (understory herbaceous plants) and water conservancy facility land, while plant biomass in grassland and cultivated land was significantly higher than that of forest land (understory herbaceous plants) and water conservancy facility land. The plant diversity index in grassland, forest land(understory herbaceous plants), and water conservancy facilities land was significantly higher than that of cultivated land. The reproductive mode and seed dispersal ability of plants in the WLFZ were the internal factors affecting the distribution pattern of vegetation, while human activities such as reservoir operation and land use types were also the main driving factors.
2026,(3):000-000, DOI: 10.18307/2026.0343
Available online: November 24, 2025
Abstract:
Poyang Lake is a typical representative of the floodplain lakes and wetlands in the middle reaches of the Yangtze River. The high-amplitude water level fluctuations undoubtedly alter the heat flux processes, profoundly affecting the surface ecological hydrological processes and local climate characteristics. To study the response mechanisms of Poyang Lake"s heat flux to the flooding process, this paper quantitatively simulates the hydrological and energy processes of the Poyang Lake floodplain wetland by using the improved VIC land surface model and its Lake module. It investigates the seasonal variation characteristics of the water-heat flux in the wetland and analyzes the driving mechanisms of the flooding process on the spatial-temporal distribution of heat flux. The results show that: (1) The model demonstrated robust performance in simulating flood dynamics and heat fluxes in Poyang Lake. For hydrological simulation, the monthly averaged water level simulations showed high consistency with observed values, achieving superior correlation coefficients (R > 0.9) and Nash-Sutcliffe Efficiency coefficients (NSE > 0.8). In thermal flux modeling, the simulated Bowen ratio exhibited strong agreement with reference values, yielding a correlation coefficient of 0.81 and NSE exceeding 0.7. This modeling framework reliably captures the hydrological rhythms and spatial heterogeneity of flood inundation in Poyang Lake, providing an effective tool for investigating eco-hydrological processes in lake wetlands under climate change scenarios; (2) In terms of temporal process, Seasonal dynamics of energy partitioning are significantly modulated by flood inundation processes in Poyang Lake. During the high-water period, extensive inundation shifts the energy allocation toward a "high latent heat–low sensible heat" state under water-dominated surfaces: 68% of net radiation is allocated to latent heat flux, driving Bowen ratio down to 0.09 (vs. 0.38 in non-inundated periods). Following emergent mudflat exposure in the dry season, latent heat contribution declines to 56%;(3) in the spatial pattern, Energy partitioning exhibits marked contrasts between the lake area and surrounding terrestrial regions: Lake-dominated zones show 29% higher latent heat flux and 59% lower sensible heat flux compared to peripheries. The northeastern high-frequency inundation area forms a persistent latent heat flux hotspot (annual mean: 89 W·m?2), exceeding levels in the southwestern low-frequency inundation zone by 80%. Spatially, latent heat flux exhibits a distinct "northeast-high to southwest-low" gradient;(4) The energy partitioning exhibits a three-stage relationship with soil moisture/water level: When the volumetric water content of the wetland surface soil is below 17%, the evaporative fraction increases relatively slowly with rising moisture content. Once the soil moisture exceeds 17%, the evaporative fraction shows a linear positive correlation with moisture content. When the soil moisture surpasses 32%, the evaporative fraction becomes decoupled from soil moisture under inundation conditions and is no longer constrained by soil moisture, demonstrating that soil moisture exerts distinct phased regulatory effects on the evaporative fraction. This study couples the land surface model VIC with underwater terrain inundation analysis to reveal the regulatory mechanism of Poyang Lake"s floodplain processes on regional energy balance. It provides a new method for understanding the water-heat exchange mechanisms in floodplain wetlands, offering important scientific insights into the ecohydrological processes of floodplain wetlands under climate change.
Poyang Lake is a typical representative of the floodplain lakes and wetlands in the middle reaches of the Yangtze River. The high-amplitude water level fluctuations undoubtedly alter the heat flux processes, profoundly affecting the surface ecological hydrological processes and local climate characteristics. To study the response mechanisms of Poyang Lake"s heat flux to the flooding process, this paper quantitatively simulates the hydrological and energy processes of the Poyang Lake floodplain wetland by using the improved VIC land surface model and its Lake module. It investigates the seasonal variation characteristics of the water-heat flux in the wetland and analyzes the driving mechanisms of the flooding process on the spatial-temporal distribution of heat flux. The results show that: (1) The model demonstrated robust performance in simulating flood dynamics and heat fluxes in Poyang Lake. For hydrological simulation, the monthly averaged water level simulations showed high consistency with observed values, achieving superior correlation coefficients (R > 0.9) and Nash-Sutcliffe Efficiency coefficients (NSE > 0.8). In thermal flux modeling, the simulated Bowen ratio exhibited strong agreement with reference values, yielding a correlation coefficient of 0.81 and NSE exceeding 0.7. This modeling framework reliably captures the hydrological rhythms and spatial heterogeneity of flood inundation in Poyang Lake, providing an effective tool for investigating eco-hydrological processes in lake wetlands under climate change scenarios; (2) In terms of temporal process, Seasonal dynamics of energy partitioning are significantly modulated by flood inundation processes in Poyang Lake. During the high-water period, extensive inundation shifts the energy allocation toward a "high latent heat–low sensible heat" state under water-dominated surfaces: 68% of net radiation is allocated to latent heat flux, driving Bowen ratio down to 0.09 (vs. 0.38 in non-inundated periods). Following emergent mudflat exposure in the dry season, latent heat contribution declines to 56%;(3) in the spatial pattern, Energy partitioning exhibits marked contrasts between the lake area and surrounding terrestrial regions: Lake-dominated zones show 29% higher latent heat flux and 59% lower sensible heat flux compared to peripheries. The northeastern high-frequency inundation area forms a persistent latent heat flux hotspot (annual mean: 89 W·m?2), exceeding levels in the southwestern low-frequency inundation zone by 80%. Spatially, latent heat flux exhibits a distinct "northeast-high to southwest-low" gradient;(4) The energy partitioning exhibits a three-stage relationship with soil moisture/water level: When the volumetric water content of the wetland surface soil is below 17%, the evaporative fraction increases relatively slowly with rising moisture content. Once the soil moisture exceeds 17%, the evaporative fraction shows a linear positive correlation with moisture content. When the soil moisture surpasses 32%, the evaporative fraction becomes decoupled from soil moisture under inundation conditions and is no longer constrained by soil moisture, demonstrating that soil moisture exerts distinct phased regulatory effects on the evaporative fraction. This study couples the land surface model VIC with underwater terrain inundation analysis to reveal the regulatory mechanism of Poyang Lake"s floodplain processes on regional energy balance. It provides a new method for understanding the water-heat exchange mechanisms in floodplain wetlands, offering important scientific insights into the ecohydrological processes of floodplain wetlands under climate change.
2026,(3):000-000, DOI: 10.18307/2026.0314
Available online: November 20, 2025
Abstract:
Phosphorus is a key nutrient element in lake ecosystems and a primary limiting factor of primary productivity. The forms and concentrations of phosphorus in water significantly influence phytoplankton community structure. To explore the characteristics of phosphorus fractions in a typical shallow lake of the middle and lower reaches of the Yangtze River—Lake Changhu—and their effects on phytoplankton community structure, and to provide a scientific basis for ecological restoration and precise management of Lake Changhu, we systematically sampled phosphorus fractions, other environmental variables, and phytoplankton communities at 10 sampling sites across the lake in March, May, September, and December 2024. Results showed that the annual mean concentration of total phosphorus (TP) in Lake Changhu was 0.117 mg/L, with a seasonal pattern of September > March > May > December and a decreasing spatial gradient from west to east. Overall, dissolved total phosphorus (DTP; mean value of 0.060 mg/L) contributed slightly more to TP than particulate phosphorus (PP; mean value of 0.056 mg/L). Specifically, PP dominated in March; in May, PP slightly exceeded DTP; whereas DTP predominated in September and December. Among dissolved phosphorus fractions, dissolved organic phosphorus (DOP) was dominant in September, while dissolved inorganic phosphorus (DIP) was dominant in December. The concentration of DOP in September was significantly higher than in other months. The dominant phytoplankton groups in Lake Changhu were Cyanophyta, Chlorophyta, Bacillariophyta, and Cryptophyta. Non-metric multidimensional scaling (NMDS) and permutational multivariate analysis of variance (PERMANOVA) showed significant differences in phytoplankton community structure among sampling months, exhibiting clear seasonal succession patterns. From March to December, the phytoplankton community transitioned from Bacillariophyta + Cryptophyta + Chlorophyta→Cyanophyta + Chlorophyta→Cyanophyta→Cryptophyta + Bacillariophyta + Cyanophyta + Chlorophyta. Specifically, Cyclotella sp. (Bacillariophyta), Merismopedia minima (Cyanophyta), and Komma caudata (Cryptophyta) were the dominant species in March, May, and December, respectively. Microcystis spp. (Cyanophyta), a bloom-forming cyanobacterium, dominated in September and was also a dominant species in May. Redundancy analysis (RDA) and partial least squares path modeling (PLS-PM) results indicated that DOP, water temperature, DTP, and suspended solids significantly influenced phytoplankton community structure, with phosphorus fractions exerting significant direct effects. Among these, DOP exhibited the strongest positive influence, particularly affecting the abundance of Microcystis spp.. In summary, our findings highlight that phosphorus fractions significantly influence the phytoplankton community structure in Lake Changhu and underscore the necessity to quantitatively assess the ecological risks of different phosphorus fractions, especially DOP, in eutrophic shallow lakes.
Phosphorus is a key nutrient element in lake ecosystems and a primary limiting factor of primary productivity. The forms and concentrations of phosphorus in water significantly influence phytoplankton community structure. To explore the characteristics of phosphorus fractions in a typical shallow lake of the middle and lower reaches of the Yangtze River—Lake Changhu—and their effects on phytoplankton community structure, and to provide a scientific basis for ecological restoration and precise management of Lake Changhu, we systematically sampled phosphorus fractions, other environmental variables, and phytoplankton communities at 10 sampling sites across the lake in March, May, September, and December 2024. Results showed that the annual mean concentration of total phosphorus (TP) in Lake Changhu was 0.117 mg/L, with a seasonal pattern of September > March > May > December and a decreasing spatial gradient from west to east. Overall, dissolved total phosphorus (DTP; mean value of 0.060 mg/L) contributed slightly more to TP than particulate phosphorus (PP; mean value of 0.056 mg/L). Specifically, PP dominated in March; in May, PP slightly exceeded DTP; whereas DTP predominated in September and December. Among dissolved phosphorus fractions, dissolved organic phosphorus (DOP) was dominant in September, while dissolved inorganic phosphorus (DIP) was dominant in December. The concentration of DOP in September was significantly higher than in other months. The dominant phytoplankton groups in Lake Changhu were Cyanophyta, Chlorophyta, Bacillariophyta, and Cryptophyta. Non-metric multidimensional scaling (NMDS) and permutational multivariate analysis of variance (PERMANOVA) showed significant differences in phytoplankton community structure among sampling months, exhibiting clear seasonal succession patterns. From March to December, the phytoplankton community transitioned from Bacillariophyta + Cryptophyta + Chlorophyta→Cyanophyta + Chlorophyta→Cyanophyta→Cryptophyta + Bacillariophyta + Cyanophyta + Chlorophyta. Specifically, Cyclotella sp. (Bacillariophyta), Merismopedia minima (Cyanophyta), and Komma caudata (Cryptophyta) were the dominant species in March, May, and December, respectively. Microcystis spp. (Cyanophyta), a bloom-forming cyanobacterium, dominated in September and was also a dominant species in May. Redundancy analysis (RDA) and partial least squares path modeling (PLS-PM) results indicated that DOP, water temperature, DTP, and suspended solids significantly influenced phytoplankton community structure, with phosphorus fractions exerting significant direct effects. Among these, DOP exhibited the strongest positive influence, particularly affecting the abundance of Microcystis spp.. In summary, our findings highlight that phosphorus fractions significantly influence the phytoplankton community structure in Lake Changhu and underscore the necessity to quantitatively assess the ecological risks of different phosphorus fractions, especially DOP, in eutrophic shallow lakes.
YAO Liangliang, ZHU Liqin, ZHANG Haikuo, MA Jie, YAN Chunmin, PU Yashuai, SONG Congqing, LI Dasheng, WANG Ling, LI Yiping
2026,(3):000-000, DOI: 10.18307/2026.0321
Available online: November 20, 2025
Abstract:
This study investigates the spatiotemporal distribution patterns and key influencing factors of carbon, nitrogen, and phosphorus in sediments of a large surface-flow constructed wetland during long-term remediation of slightly polluted water.We collected sediment samples from 28 sites in Yanlong Lake and analyzed the contents of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP). Correlation analyses were performed among these parameters, followed by comprehensive pollution and organic pollution assessments. Results revealed average concentrations of 529 mg/kg TP, 953 mg/kg TN, and 0.85% TOC in the sediments. Strong positive correlations were observed between TN and TP (r=0.729, P<0.01) and between TN and TOC (r=0.251, P<0.05), suggesting shared organic sources for nitrogen and carbon. Key spatial patterns emerged: ① Along the water flow direction, TP and TN contents showed decreasing trends across different zones, with the pretreatment area exhibiting the highest nutrient levels and most severe pollution; ② Vertical distribution displayed surface enrichment (0-30 cm) of nutrients across all zones. Compared to 2017 data, the emergent plant zone demonstrated decreasing nutrient trends along flow direction but higher TP and TOC contents, attributable to accumulated algal debris, particle-bound pollutants, and microbial-mediated nutrient release at the inlet area. Pollution assessment using comprehensive and organic pollution indices indicated generally good sediment quality throughout Yanlong Lake. Nitrogen and phosphorus pollution ranged from moderate in the pretreatment zone to clean/mild in other areas, while organic pollution was mild only in pretreatment and advanced treatment zones but clean elsewhere. These findings provide valuable scientific references for sediment pollution evaluation in large surface-flow constructed wetlands during extended operation.
This study investigates the spatiotemporal distribution patterns and key influencing factors of carbon, nitrogen, and phosphorus in sediments of a large surface-flow constructed wetland during long-term remediation of slightly polluted water.We collected sediment samples from 28 sites in Yanlong Lake and analyzed the contents of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP). Correlation analyses were performed among these parameters, followed by comprehensive pollution and organic pollution assessments. Results revealed average concentrations of 529 mg/kg TP, 953 mg/kg TN, and 0.85% TOC in the sediments. Strong positive correlations were observed between TN and TP (r=0.729, P<0.01) and between TN and TOC (r=0.251, P<0.05), suggesting shared organic sources for nitrogen and carbon. Key spatial patterns emerged: ① Along the water flow direction, TP and TN contents showed decreasing trends across different zones, with the pretreatment area exhibiting the highest nutrient levels and most severe pollution; ② Vertical distribution displayed surface enrichment (0-30 cm) of nutrients across all zones. Compared to 2017 data, the emergent plant zone demonstrated decreasing nutrient trends along flow direction but higher TP and TOC contents, attributable to accumulated algal debris, particle-bound pollutants, and microbial-mediated nutrient release at the inlet area. Pollution assessment using comprehensive and organic pollution indices indicated generally good sediment quality throughout Yanlong Lake. Nitrogen and phosphorus pollution ranged from moderate in the pretreatment zone to clean/mild in other areas, while organic pollution was mild only in pretreatment and advanced treatment zones but clean elsewhere. These findings provide valuable scientific references for sediment pollution evaluation in large surface-flow constructed wetlands during extended operation.
2026,(3):000-000, DOI: 10.18307/2026.0327
Available online: November 18, 2025
Abstract:
Reservoirs, while regulating runoff, profoundly alter the carbon flux and storage along river continua, playing a critical regulatory role in the global carbon cycle. The carbon source–sink dynamics of reservoirs are influenced by various factors, including natural conditions, reservoir characteristics, and operational management. However, observations and studies on the dynamic changes in CO2 fluxes at the water–air interface of reservoirs under different hydrological conditions remain scarce, severely limiting the accuracy of carbon budget assessments. This study focused on the Danjiangkou Reservoir located in the subtropical monsoon region. Based on eddy covariance observations from April 2022 to February 2024, and employing a Structural Equation Model (SEM), the seasonal variations in CO2 fluxes at the water–air interface and their influencing factors during wet and dry periods were quantitatively analyzed. The results showed that the annual mean CO2 flux of the Danjiangkou Reservoir was 0.12 ± 1.93 μmol/(m2.s), indicating a weak carbon source overall, with pronounced seasonal variation. During the wet period (April to October), the reservoir acted as a carbon source (0.97 ± 1.22 μmol/(m2.s)), whereas during the dry period (November to March), it shifted to a carbon sink (?1.13 ± 2.04 μmol/(m2.s)). SEM analysis revealed that energy-related factors, especially sensible heat flux was the most direct and significantly negative influencing factor of CO2 fluxes in both periods, with stronger effects during the dry season. In the wet period, inflow and physical water properties significantly enhanced CO2 emissions through direct effects, while in the dry season, the influence of phytoplankton and nutrients shifted from positive to negative, indicating an increased contribution of biological processes to CO2 uptake. These findings highlights the seasonal source–sink dynamics and driving mechanisms of CO2 fluxes in the Danjiangkou Reservoir under different hydrological regimes, providing a scientific basis for reservoir carbon budget assessments and carbon-oriented management strategies.
Reservoirs, while regulating runoff, profoundly alter the carbon flux and storage along river continua, playing a critical regulatory role in the global carbon cycle. The carbon source–sink dynamics of reservoirs are influenced by various factors, including natural conditions, reservoir characteristics, and operational management. However, observations and studies on the dynamic changes in CO2 fluxes at the water–air interface of reservoirs under different hydrological conditions remain scarce, severely limiting the accuracy of carbon budget assessments. This study focused on the Danjiangkou Reservoir located in the subtropical monsoon region. Based on eddy covariance observations from April 2022 to February 2024, and employing a Structural Equation Model (SEM), the seasonal variations in CO2 fluxes at the water–air interface and their influencing factors during wet and dry periods were quantitatively analyzed. The results showed that the annual mean CO2 flux of the Danjiangkou Reservoir was 0.12 ± 1.93 μmol/(m2.s), indicating a weak carbon source overall, with pronounced seasonal variation. During the wet period (April to October), the reservoir acted as a carbon source (0.97 ± 1.22 μmol/(m2.s)), whereas during the dry period (November to March), it shifted to a carbon sink (?1.13 ± 2.04 μmol/(m2.s)). SEM analysis revealed that energy-related factors, especially sensible heat flux was the most direct and significantly negative influencing factor of CO2 fluxes in both periods, with stronger effects during the dry season. In the wet period, inflow and physical water properties significantly enhanced CO2 emissions through direct effects, while in the dry season, the influence of phytoplankton and nutrients shifted from positive to negative, indicating an increased contribution of biological processes to CO2 uptake. These findings highlights the seasonal source–sink dynamics and driving mechanisms of CO2 fluxes in the Danjiangkou Reservoir under different hydrological regimes, providing a scientific basis for reservoir carbon budget assessments and carbon-oriented management strategies.
2026,(3):000-000, DOI: 10.18307/2026.0312
Available online: November 18, 2025
Abstract:
The Danjiangkou Reservoir is a key water source for the South-to-North Water Diversion Project"s middle route and a national first-level water source protection zone. Since water began flowing in 2014, the overall water quality in the reservoir area has remained at Class II or higher, playing an important ecological and water resource protection role. Water level fluctuations, as a crucial parameter in reservoir operation, directly affect the environmental characteristics of the water body, thereby indirectly influencing the growth, distribution, and diversity of phytoplankton. To investigate the impact of habitat changes induced by water level fluctuations on the functional groups of phytoplankton in the Danjiangkou Reservoir, this study selected high-water periods (October–December 2023) and low-water periods (April–June 2024) for sampling and analysis. The study analyzed the structure and composition of phytoplankton functional groups and the environmental factors influencing these groups. The results showed that a total of 128 species belonging to 75 genera and 7 phyla of phytoplankton were identified under different temporal and spatial conditions in the Danjiangkou Reservoir. The main phytoplankton phyla were Bacillariophyta (39.06%), Chlorophyta (35.94%), and Cyanophyta (10.16%). There were significant differences in the composition of phytoplankton functional groups between different temporal and spatial conditions (p < 0.05). A total of 26 functional groups were classified, including functional groups N and P that adapt to mixed water column environments, functional groups Y and T adapted to still water environments, and universal functional groups M and Lo. During the high-water period, the dominant functional group in the reservoir area was group B; while during the low-water period, the dominant functional groups were MP, P, and Lo. In the tributaries, the dominant functional groups during the high-water period were M, Lo, and S1, while during the low-water period, the dominant functional groups were TC and B. The results of the Redundancy Analysis (RDA) indicated that pH, turbidity, NO3-N, and PO43--P were the main environmental factors affecting the dominant functional groups of phytoplankton. Water quality evaluation based on the Q-index showed that the water quality in the reservoir area was generally in a "good" state, while the water quality in the tributary area ranged from "poor" to "good." The study suggests that while the water quality in the main reservoir area is generally stable, the tributaries experience significant interference from nutrient pollution on phytoplankton communities during the high-water period, highlighting the need for reservoir management to focus on the potential impact of external inputs during high-water periods on the ecosystem.
The Danjiangkou Reservoir is a key water source for the South-to-North Water Diversion Project"s middle route and a national first-level water source protection zone. Since water began flowing in 2014, the overall water quality in the reservoir area has remained at Class II or higher, playing an important ecological and water resource protection role. Water level fluctuations, as a crucial parameter in reservoir operation, directly affect the environmental characteristics of the water body, thereby indirectly influencing the growth, distribution, and diversity of phytoplankton. To investigate the impact of habitat changes induced by water level fluctuations on the functional groups of phytoplankton in the Danjiangkou Reservoir, this study selected high-water periods (October–December 2023) and low-water periods (April–June 2024) for sampling and analysis. The study analyzed the structure and composition of phytoplankton functional groups and the environmental factors influencing these groups. The results showed that a total of 128 species belonging to 75 genera and 7 phyla of phytoplankton were identified under different temporal and spatial conditions in the Danjiangkou Reservoir. The main phytoplankton phyla were Bacillariophyta (39.06%), Chlorophyta (35.94%), and Cyanophyta (10.16%). There were significant differences in the composition of phytoplankton functional groups between different temporal and spatial conditions (p < 0.05). A total of 26 functional groups were classified, including functional groups N and P that adapt to mixed water column environments, functional groups Y and T adapted to still water environments, and universal functional groups M and Lo. During the high-water period, the dominant functional group in the reservoir area was group B; while during the low-water period, the dominant functional groups were MP, P, and Lo. In the tributaries, the dominant functional groups during the high-water period were M, Lo, and S1, while during the low-water period, the dominant functional groups were TC and B. The results of the Redundancy Analysis (RDA) indicated that pH, turbidity, NO3-N, and PO43--P were the main environmental factors affecting the dominant functional groups of phytoplankton. Water quality evaluation based on the Q-index showed that the water quality in the reservoir area was generally in a "good" state, while the water quality in the tributary area ranged from "poor" to "good." The study suggests that while the water quality in the main reservoir area is generally stable, the tributaries experience significant interference from nutrient pollution on phytoplankton communities during the high-water period, highlighting the need for reservoir management to focus on the potential impact of external inputs during high-water periods on the ecosystem.
2026,(3):000-000, DOI: 10.18307/2026.0322
Available online: November 18, 2025
Abstract:
To understand the impact of Xiaolangdi water and sediment regulation on nitrogen migration, transformation in the lower Yellow River and flux to the sea, the surface water samples were collected from two hydrological stations near the reservoir outlet (Huayuankou, HYK) and the river mouth (Lijin Station, LJ) in six times, including before, during, and after water and sediment regulation in 2023. River flow rates, suspended sediment, total nitrogen (TN), water-phase and suspended-phase nitrate nitrogen (NO3--N), ammonium nitrogen (NH4+-N) concentrations, and nitrate nitrogen isotopes (δ15N-NO3- and δ18O-NO3-) were analyzed. The results showed that the flow rates at HYK and LJ stations rosed to maximum of 4350 and 2860m3·s-1, respectively, the TN concentration decreased due to the release of large amounts of clear water, NO3--N concentrations in the water phase increased, while that in the suspended phase decreased during the water regulation stage. Meanwhile, the δ18O-NO3- value in the water phase decreased, and the concentration of NH4+-N in the suspended phase first increased and then decreased. The results indicated that large amounts of clear water flushed the external nitrogen into the water body, and mineration and nitrification occurred during the water regualtion stage, which caused NO3--N concentration in the water phase to increase. Meanwhile, the scouring flow disturbed riverbed sediments, causing their resuspension and the release of NH4+-N into the water phase. As the water regulation progressed, NH4+-N adsorbed on suspended sediments was further mobilized into the water phase. During the sediment regulation stage, the flow rates at HYK and LJ stations first rose to peaks of 4,010 and 3,480 m3/s, then declined to 591 and 726 m3/s, respectively. The sediment concentrations increased significantly, reaching a maximum of 44.6 and 31.6 g·L-1, respectively during the sediment regulation. Meanwhile, TN, NO3--N and NH4+-N concentrations in the water phase and suspended phase decreased significantly from the pre-sediment to the post-sediment regualtion stage, and NO3--N concentrations at LJ station decreased more than those at HYK station. Compared with the water regulation stage, the δ15N-NO3- in the suspended phase increased during sediment regulation. The δ15N-NO3- values increased and NO3--N concentrations decreased in the suspended phase along the flow direction. This indicated that the coupling effect of nitrification and denitrification occurred during the water and sediment regulation stage. Based on the TN flux calculation at LJ station, the TN flux into the sea was the highest in the post-water regulation stage (1867 t·d-1), followed by pre-sediment regulation stage (1724 t·d-1) and the pre-water regulation stage (1102 t·d-1). The research results will provide a scientific basis for the relationship between water and sediment changes and nitrogen output changes in the lower reaches of the Yellow River.
To understand the impact of Xiaolangdi water and sediment regulation on nitrogen migration, transformation in the lower Yellow River and flux to the sea, the surface water samples were collected from two hydrological stations near the reservoir outlet (Huayuankou, HYK) and the river mouth (Lijin Station, LJ) in six times, including before, during, and after water and sediment regulation in 2023. River flow rates, suspended sediment, total nitrogen (TN), water-phase and suspended-phase nitrate nitrogen (NO3--N), ammonium nitrogen (NH4+-N) concentrations, and nitrate nitrogen isotopes (δ15N-NO3- and δ18O-NO3-) were analyzed. The results showed that the flow rates at HYK and LJ stations rosed to maximum of 4350 and 2860m3·s-1, respectively, the TN concentration decreased due to the release of large amounts of clear water, NO3--N concentrations in the water phase increased, while that in the suspended phase decreased during the water regulation stage. Meanwhile, the δ18O-NO3- value in the water phase decreased, and the concentration of NH4+-N in the suspended phase first increased and then decreased. The results indicated that large amounts of clear water flushed the external nitrogen into the water body, and mineration and nitrification occurred during the water regualtion stage, which caused NO3--N concentration in the water phase to increase. Meanwhile, the scouring flow disturbed riverbed sediments, causing their resuspension and the release of NH4+-N into the water phase. As the water regulation progressed, NH4+-N adsorbed on suspended sediments was further mobilized into the water phase. During the sediment regulation stage, the flow rates at HYK and LJ stations first rose to peaks of 4,010 and 3,480 m3/s, then declined to 591 and 726 m3/s, respectively. The sediment concentrations increased significantly, reaching a maximum of 44.6 and 31.6 g·L-1, respectively during the sediment regulation. Meanwhile, TN, NO3--N and NH4+-N concentrations in the water phase and suspended phase decreased significantly from the pre-sediment to the post-sediment regualtion stage, and NO3--N concentrations at LJ station decreased more than those at HYK station. Compared with the water regulation stage, the δ15N-NO3- in the suspended phase increased during sediment regulation. The δ15N-NO3- values increased and NO3--N concentrations decreased in the suspended phase along the flow direction. This indicated that the coupling effect of nitrification and denitrification occurred during the water and sediment regulation stage. Based on the TN flux calculation at LJ station, the TN flux into the sea was the highest in the post-water regulation stage (1867 t·d-1), followed by pre-sediment regulation stage (1724 t·d-1) and the pre-water regulation stage (1102 t·d-1). The research results will provide a scientific basis for the relationship between water and sediment changes and nitrogen output changes in the lower reaches of the Yellow River.
2026,(3):000-000, DOI: 10.18307/2026.0300
Available online: November 14, 2025
Abstract:
Algal blooms caused by phytoplankton overgrowth pose a common challenge for lake management worldwide. In China, current strategies primarily rely on environmental standards such as the “Environmental Quality Standards for Surface Water”, using total nitrogen and total phosphorus concentrations as key control targets. However, these efforts often yield limited success despite high investment. Notably, in many lakes, algal bloom intensity has increased even as nutrient concentrations stabilized or declined, highlighting a disconnect between static nutrient criteria and the dynamic growth responses of phytoplankton. The theory of limiting factors provides a scientific basis for building a precision control system. Based on Liebig’s law of the minimum and Blackman’s law of limiting factors, this review synthesizes multiple constraints on phytoplankton growth, including nutrients (e.g., nitrogen, phosphorus), trace elements, light, temperature, and ecological interactions such as grazing and macrophyte competition. We evaluate the strengths and limitations of four diagnostic approaches: experimental assays, empirical thresholds, residual analysis, and regression modeling. Three priority research directions are proposed: (1) clarifying the context-specific applicability of nitrogen reduction across lake types; (2) establishing a “climate potential–realized performance” framework for assessing nutrient assimilation efficiency; and (3) investigating how non-classical food web interactions influence bloom dynamics in shallow lakes. This study aims to support the transition from generalized nutrient control toward precision eco-management strategies for algal blooms in Chinese lakes.
Algal blooms caused by phytoplankton overgrowth pose a common challenge for lake management worldwide. In China, current strategies primarily rely on environmental standards such as the “Environmental Quality Standards for Surface Water”, using total nitrogen and total phosphorus concentrations as key control targets. However, these efforts often yield limited success despite high investment. Notably, in many lakes, algal bloom intensity has increased even as nutrient concentrations stabilized or declined, highlighting a disconnect between static nutrient criteria and the dynamic growth responses of phytoplankton. The theory of limiting factors provides a scientific basis for building a precision control system. Based on Liebig’s law of the minimum and Blackman’s law of limiting factors, this review synthesizes multiple constraints on phytoplankton growth, including nutrients (e.g., nitrogen, phosphorus), trace elements, light, temperature, and ecological interactions such as grazing and macrophyte competition. We evaluate the strengths and limitations of four diagnostic approaches: experimental assays, empirical thresholds, residual analysis, and regression modeling. Three priority research directions are proposed: (1) clarifying the context-specific applicability of nitrogen reduction across lake types; (2) establishing a “climate potential–realized performance” framework for assessing nutrient assimilation efficiency; and (3) investigating how non-classical food web interactions influence bloom dynamics in shallow lakes. This study aims to support the transition from generalized nutrient control toward precision eco-management strategies for algal blooms in Chinese lakes.
Wu Tongfei, Lu Taoxiu, Lyu Hongjian, Ding Yuwei, Yang Li, Tian Zhili, Xi Dan, Deng Huatang, Yao Weizhi, Fu Mei
2026,(3):000-000, DOI: 10.18307/2026.0332
Available online: November 12, 2025
Abstract:
The current study aims to investigate the reproductive status and adaptive strategies of Coilia nasus in the Three Gorges Reservoir Region (TGRR). A total of 388 specimens were collected from the Wushan to Fuling section, which is the core area of the TGRR, between June and August 2021 to 2023. The analysis revealed that the current age structure of the C. nasus population is stable, with a female-to-male sex ratio of 0.92:1 in the spawning population. The youngest sexually mature individuals were 1 year old for both sexes. The females’ biological minimum size was 152.5 mm in body length and 11.96 g in body weight, while the males’ was 166.6 mm and 17.64 g, respectively. The average absolute fecundity and relative fecundity of C. nasus were (3.10±2.16)×104 eggs and (605.42±181.85) eggs/g, respectively. The egg diameter was (615.47±107.30) μm on average, and exhibited a unimodal distribution, which indicated a single spawning type. The average gonadosomatic index (GSI) was (6.32±4.52)% for females and (3.74±1.63)% for males, while the average hepatosomatic index (HSI) was (1.15±1.10)% for females and (0.63±0.53)% for males, respectively. Compared with the studies on C. nasus in the TGRR and other Yangtze River waters prior, the current spawning population in the TGRR tends to be shifting towards characteristics of an r-strategist, which is reducing egg size and increasing absolute fecundity. In conclusion, the stable population structure and size of C. nasus suggest that it has fully adapted to the environment of the TGRR. Its distribution range is likely to expand further into other upstream waters of the Yangtze River, including both the mainstem and its tributaries.
The current study aims to investigate the reproductive status and adaptive strategies of Coilia nasus in the Three Gorges Reservoir Region (TGRR). A total of 388 specimens were collected from the Wushan to Fuling section, which is the core area of the TGRR, between June and August 2021 to 2023. The analysis revealed that the current age structure of the C. nasus population is stable, with a female-to-male sex ratio of 0.92:1 in the spawning population. The youngest sexually mature individuals were 1 year old for both sexes. The females’ biological minimum size was 152.5 mm in body length and 11.96 g in body weight, while the males’ was 166.6 mm and 17.64 g, respectively. The average absolute fecundity and relative fecundity of C. nasus were (3.10±2.16)×104 eggs and (605.42±181.85) eggs/g, respectively. The egg diameter was (615.47±107.30) μm on average, and exhibited a unimodal distribution, which indicated a single spawning type. The average gonadosomatic index (GSI) was (6.32±4.52)% for females and (3.74±1.63)% for males, while the average hepatosomatic index (HSI) was (1.15±1.10)% for females and (0.63±0.53)% for males, respectively. Compared with the studies on C. nasus in the TGRR and other Yangtze River waters prior, the current spawning population in the TGRR tends to be shifting towards characteristics of an r-strategist, which is reducing egg size and increasing absolute fecundity. In conclusion, the stable population structure and size of C. nasus suggest that it has fully adapted to the environment of the TGRR. Its distribution range is likely to expand further into other upstream waters of the Yangtze River, including both the mainstem and its tributaries.
2026,(3):000-000, DOI: 10.18307/2026.0342
Available online: November 06, 2025
Abstract:
Abstract: Lake topography, as a core element of the geographical environment, holds multifaceted significance in geographical research. It exerts fundamental influence on surface processes, particularly in hydrological and hydrodynamic modeling. Given that traditional methods for acquiring bathymetric data in large lakes are cost-intensive, time-consuming, and yield infrequent updates, it is imperative to develop rapid satellite remote sensing-based approaches for lake topography mapping. This study utilizes the Random Forest (RF) algorithm combined with Landsat remote sensing imagery and measured elevation data to inverse the local topography of Poyang Lake during the dry season. To address the spatial non-stationarity of topographic features and the spatial autocorrelation of prediction residuals, this study integrates Geographically Weighted Regression (GWR) with Ordinary Kriging (OK) methods to optimize the inversion results and analyzes its errors. The results show that: (1) compared with the RF model, the accuracy of the geographically weighted regression random forest kriging hybrid model (GWR-RF-OK) is significantly improved, and the coefficient of determination (R2) of the measured and inverted elevations in the two study areas are increased, and the mean absolute error (MAE) and mean relative error (MRE) are decreased. (2) The hybrid model has better inversion effect in both the bare beach area with single surface cover type and the Nanji Wetland National Nature Reserve of Poyang Lake (hereinafter referred to as Nanji Wetland Area), which has relatively complex surface cover types, with the R2 of 0.71 and 0.56, the MAE of 0.34m and 0.35m, and the MRE of 5.26% and 3.06%, respectively. After segmentation analysis, the model has better inversion effect in areas with topographic elevation greater than 10m. (3) The degree of topographic relief and the type of surface cover affects the accuracy of the inversion, with the error being smaller in areas with gentle topography than in areas with steep topography, and the accuracy of the topographic inversion of the same type of surface cover in areas with a single surface cover is significantly better than that in areas with a mixture of multiple surface cover types.
Abstract: Lake topography, as a core element of the geographical environment, holds multifaceted significance in geographical research. It exerts fundamental influence on surface processes, particularly in hydrological and hydrodynamic modeling. Given that traditional methods for acquiring bathymetric data in large lakes are cost-intensive, time-consuming, and yield infrequent updates, it is imperative to develop rapid satellite remote sensing-based approaches for lake topography mapping. This study utilizes the Random Forest (RF) algorithm combined with Landsat remote sensing imagery and measured elevation data to inverse the local topography of Poyang Lake during the dry season. To address the spatial non-stationarity of topographic features and the spatial autocorrelation of prediction residuals, this study integrates Geographically Weighted Regression (GWR) with Ordinary Kriging (OK) methods to optimize the inversion results and analyzes its errors. The results show that: (1) compared with the RF model, the accuracy of the geographically weighted regression random forest kriging hybrid model (GWR-RF-OK) is significantly improved, and the coefficient of determination (R2) of the measured and inverted elevations in the two study areas are increased, and the mean absolute error (MAE) and mean relative error (MRE) are decreased. (2) The hybrid model has better inversion effect in both the bare beach area with single surface cover type and the Nanji Wetland National Nature Reserve of Poyang Lake (hereinafter referred to as Nanji Wetland Area), which has relatively complex surface cover types, with the R2 of 0.71 and 0.56, the MAE of 0.34m and 0.35m, and the MRE of 5.26% and 3.06%, respectively. After segmentation analysis, the model has better inversion effect in areas with topographic elevation greater than 10m. (3) The degree of topographic relief and the type of surface cover affects the accuracy of the inversion, with the error being smaller in areas with gentle topography than in areas with steep topography, and the accuracy of the topographic inversion of the same type of surface cover in areas with a single surface cover is significantly better than that in areas with a mixture of multiple surface cover types.
Xinfeng Zhuang, Haoran Tang, Xingchen Zhao, Yaxuan Li, Jin Wang, Minglei Ren, Ze Ren, Wei Zhang, Jihong Peng, Jianming Deng
2026,(3):000-000, DOI: 10.18307/2026.0338
Available online: November 06, 2025
Abstract:
In the context of global climate change, the frequency and intensity of extreme heat events (heat waves) have increased significantly, posing potential threats to the stability of lake ecosystems. To assess these impacts, this study simulated short-term heat waves using the Middle Universe Simulation System. A combined metagenomic and metatranscriptomic sequencing approach was applied to systematically examine structural and functional responses of lake aquatic microbial communities. The results showed that microbial community composition remained largely stable under short-term high-temperature stress, whereas functional diversity increased markedly, with 467 unique functions detected compared to the control group. Moreover, gene expression levels exhibited substantial changes, particularly in metabolic pathways and photosynthetic processes. The Bray–Curtis analysis further revealed an increase of 0.12 in community compositional distance and 0.16 in functional distance following heat wave exposure. These findings indicate that heat waves primarily affect aquatic ecological processes by driving shifts in functional diversity. Overall, aquatic microbial communities appear capable of rapidly adapting to environmental fluctuations through functional adjustments, while structural changes occur more slowly.
In the context of global climate change, the frequency and intensity of extreme heat events (heat waves) have increased significantly, posing potential threats to the stability of lake ecosystems. To assess these impacts, this study simulated short-term heat waves using the Middle Universe Simulation System. A combined metagenomic and metatranscriptomic sequencing approach was applied to systematically examine structural and functional responses of lake aquatic microbial communities. The results showed that microbial community composition remained largely stable under short-term high-temperature stress, whereas functional diversity increased markedly, with 467 unique functions detected compared to the control group. Moreover, gene expression levels exhibited substantial changes, particularly in metabolic pathways and photosynthetic processes. The Bray–Curtis analysis further revealed an increase of 0.12 in community compositional distance and 0.16 in functional distance following heat wave exposure. These findings indicate that heat waves primarily affect aquatic ecological processes by driving shifts in functional diversity. Overall, aquatic microbial communities appear capable of rapidly adapting to environmental fluctuations through functional adjustments, while structural changes occur more slowly.
2026,(3):000-000, DOI: 10.18307/2026.0336
Available online: November 06, 2025
Abstract:
The lake area in the middle and lower reaches of the Yangtze River represents a significant concentration of freshwater lakes in China, with its biodiversity facing considerable challenges stemming from prolonged river-lake disconnection. While previous research has examined the impacts of river-lake disconnection on aquatic biodiversity, there remains a dearth of studies focusing on the taxonomic distinctness diversity of mollusk communities over long-term scales. To address this gap, this study selected seven representative lakes (comprising five disconnected lakes and two remaining connected lakes) in the middle and lower reaches of the Yangtze River, to investigate changes in the taxonomic distinctness indices of mollusk communities by comparing data from historical and contemporary periods. The findings revealed a notable decline in total species richness (from 152 to 83 species), with the average species richness decreasing from 57.7 to 30.1 (a 47.8% reduction). From the historical period to current period, the average taxonomic distinctness Δ+ and variation in taxonomic distinctness Λ+ of entire mollusks, gastropods and bivalves all remained relatively stable, except for a significant increase in the Δ+ of gastropods. Compared to the two connected lakes, the five disconnected lakes exhibited more pronounced changes in Δ+ and Λ+ indices: the Δ+ of entire mollusks (t = -3.551，p = 0.024) and gastropods (t = -2.774，p = 0.050) both significantly increased over time,while the Λ+ of entire mollusks significantly decreased(t = 2.297，p = 0.083). Additionally, in the funnel plot analysis based on the Δ+ and Λ+ indices, the disconnected lakes were predominantly located within the 95% confidence interval, while the connected lakes fell outside this range. The increase in Δ+ and decrease in Λ+ observed in mollusk communities across the five disconnected lakes were primarily driven by the significant loss of congeneric and endemic species (such as with the genera Sinotaia,Cipangopaludina,Lamprotula,and Aculamprotula). Such loss of these congeneric endemic species from the families Viviparidae and Unionidae should be regarded as a critical warning signal of biodiversity decline caused by river-lake disconnection. The findings provide scientific basis for the management and conservation of mollusk resources and diversity,as well as the ecological restoration of lakes in the middle and lower reaches of the Yangtze River under the background of river-lake disconnection.
The lake area in the middle and lower reaches of the Yangtze River represents a significant concentration of freshwater lakes in China, with its biodiversity facing considerable challenges stemming from prolonged river-lake disconnection. While previous research has examined the impacts of river-lake disconnection on aquatic biodiversity, there remains a dearth of studies focusing on the taxonomic distinctness diversity of mollusk communities over long-term scales. To address this gap, this study selected seven representative lakes (comprising five disconnected lakes and two remaining connected lakes) in the middle and lower reaches of the Yangtze River, to investigate changes in the taxonomic distinctness indices of mollusk communities by comparing data from historical and contemporary periods. The findings revealed a notable decline in total species richness (from 152 to 83 species), with the average species richness decreasing from 57.7 to 30.1 (a 47.8% reduction). From the historical period to current period, the average taxonomic distinctness Δ+ and variation in taxonomic distinctness Λ+ of entire mollusks, gastropods and bivalves all remained relatively stable, except for a significant increase in the Δ+ of gastropods. Compared to the two connected lakes, the five disconnected lakes exhibited more pronounced changes in Δ+ and Λ+ indices: the Δ+ of entire mollusks (t = -3.551，p = 0.024) and gastropods (t = -2.774，p = 0.050) both significantly increased over time,while the Λ+ of entire mollusks significantly decreased(t = 2.297，p = 0.083). Additionally, in the funnel plot analysis based on the Δ+ and Λ+ indices, the disconnected lakes were predominantly located within the 95% confidence interval, while the connected lakes fell outside this range. The increase in Δ+ and decrease in Λ+ observed in mollusk communities across the five disconnected lakes were primarily driven by the significant loss of congeneric and endemic species (such as with the genera Sinotaia,Cipangopaludina,Lamprotula,and Aculamprotula). Such loss of these congeneric endemic species from the families Viviparidae and Unionidae should be regarded as a critical warning signal of biodiversity decline caused by river-lake disconnection. The findings provide scientific basis for the management and conservation of mollusk resources and diversity,as well as the ecological restoration of lakes in the middle and lower reaches of the Yangtze River under the background of river-lake disconnection.
2026,(3):000-000, DOI: 10.18307/2026.0341
Available online: November 05, 2025
Abstract:
Residence time serves as a critical indicator of lake water renewal and exchange, directly influencing pollutant transport and migration processes, and consequently water environment of the lake. In recent years, the hydrological conditions of Poyang Lake have undergone substantial changes, which have significantly influenced its water environment. This study focuses on residence time as a crucial hydrodynamic parameter for assessing water quality. Using the MIKE21 hydrodynamic model coupled with a tracer model, the research quantitatively examines the spatiotemporal distribution characteristics of residence time during the receding period of Poyang Lake from 1980 to 2020. Additionally, the study investigates regional interannual variation trends and clarifies the response relationship between residence time and hydrological conditions. The results reveal that the residence time during the receding period of Poyang Lake is characterized by high spatiotemporal heterogeneity. The average residence time for the entire lake is 36 d, with variations among sub-regions: eastern lake bays (93 d) > southern lake area (53 d) > northern channels (38 d) > main lake area (26 d) > seasonal isolated lakes of Wucheng (17 d). Over the past 40 years, certain areas of Poyang Lake have experienced a slight decreasing trend in average residence time. After the operation of Three Gorges Dam, the average residence time of the entire lake decreases by about 4 d, with the northern channels exhibiting the largest decrease (9 d), followed by the main lake area (5 d); other regions show minimal change. The residence time during the receding period of Poyang Lake is significantly longer in wet years compared to dry years. A strong positive correlation exists between residence rate and water level during the receding period. The shortened residence time during the receding period in Poyang Lake is primarily attributed to the decreased water level and the accelerated recession rate. The results of this study can provide scientific support for the water environment governance and ecological restoration of Poyang Lake.
Residence time serves as a critical indicator of lake water renewal and exchange, directly influencing pollutant transport and migration processes, and consequently water environment of the lake. In recent years, the hydrological conditions of Poyang Lake have undergone substantial changes, which have significantly influenced its water environment. This study focuses on residence time as a crucial hydrodynamic parameter for assessing water quality. Using the MIKE21 hydrodynamic model coupled with a tracer model, the research quantitatively examines the spatiotemporal distribution characteristics of residence time during the receding period of Poyang Lake from 1980 to 2020. Additionally, the study investigates regional interannual variation trends and clarifies the response relationship between residence time and hydrological conditions. The results reveal that the residence time during the receding period of Poyang Lake is characterized by high spatiotemporal heterogeneity. The average residence time for the entire lake is 36 d, with variations among sub-regions: eastern lake bays (93 d) > southern lake area (53 d) > northern channels (38 d) > main lake area (26 d) > seasonal isolated lakes of Wucheng (17 d). Over the past 40 years, certain areas of Poyang Lake have experienced a slight decreasing trend in average residence time. After the operation of Three Gorges Dam, the average residence time of the entire lake decreases by about 4 d, with the northern channels exhibiting the largest decrease (9 d), followed by the main lake area (5 d); other regions show minimal change. The residence time during the receding period of Poyang Lake is significantly longer in wet years compared to dry years. A strong positive correlation exists between residence rate and water level during the receding period. The shortened residence time during the receding period in Poyang Lake is primarily attributed to the decreased water level and the accelerated recession rate. The results of this study can provide scientific support for the water environment governance and ecological restoration of Poyang Lake.
2026,(3):000-000, DOI: 10.18307/2026.0324
Available online: November 05, 2025
Abstract:
As a strategic water conservancy project in the lower reaches of the Yangtze River in China, the project has multiple missions such as alleviating the shortage of water resources in Huaibei, improving the ecology of Chaohu Lake and Huaihe River, and promoting the sustainable development of the river basin. Dissolved organic matter (DOM) is an important indicator for assessing the health status of water bodies and tracing pollution sources. Study on its response process to inter-basin water transfers can accurately track the characteristics of water quality changes induced by such transfers, which is of great significance for optimizing ecological scheduling strategies and ensuring water environmental security in the Jiang-huai region. In this study, we selected the Yangtze-Chao section and Yangtze-Huai section in the water diversion project from the Yangtze River to Huaihe River (Anhui section), systematically analysed the source, composition and distribution characteristics of dissolved organic matter (DOM) and its influencing factors in the water diversion project (Anhui section) from the Yangtze River to Huaihe River at the different hydrological periods from December 2023 to June 2024. The results show as follows: (1) the concentration of total nitrogen (TN), ammonia nitrogen and permanganate index (CODMn) in the water bodies during the different hydrological periods showed increasing trends in the dry season, wet season and normal flow season, and their concentrations decreased after water diversion, especially in the Yangtze-Huai section the concentration of TN decreasing from 4.00±1.45 mg/L to 2.06±0.58 mg/L. TP concentration did not change with the spatial and seasonal distributions. DOC concentration showed significant seasonal and spatial variation. During the dry season, the concentrations of DOC in lakes and estuaries were relatively high, while DOC in river section was low. (2) Four DOM fluorescent components were identified, namely marine-derived humus C1, funic acid humic C2, humic acid C3, and tryptophan group proteins C4. DOM was both influenced by autogenic and terrestrial sources. There is no significant seasonal variation in the proportion of autogenic and terrestrial organic matter in the water during different hydrological periods. After water regulation, there is no obvious difference in the spatial distribution characteristics of DOM fluorescence intensity and DOC concentration due to water exchange. (3) TN, CODMn, DO, Chl-a and WT had a significant impact on the composition and concentration of DOM, while the increase of water temperature and DO had a promoting effect on algae growth and degradation of organic matter. The increase of TN concentration led to the eutrophication of water body and the accumulation of DOM. This study evaluated the water environment quality along the Anhui section of the Yangtze-to-Huaihe water diversion project after its initial implementation of water diversion. It reveals the response patterns of DOM in the early stages of inter-basin water transfer and provides a scientific basis for scheduling the water diversion project from a water quality safety perspective.
As a strategic water conservancy project in the lower reaches of the Yangtze River in China, the project has multiple missions such as alleviating the shortage of water resources in Huaibei, improving the ecology of Chaohu Lake and Huaihe River, and promoting the sustainable development of the river basin. Dissolved organic matter (DOM) is an important indicator for assessing the health status of water bodies and tracing pollution sources. Study on its response process to inter-basin water transfers can accurately track the characteristics of water quality changes induced by such transfers, which is of great significance for optimizing ecological scheduling strategies and ensuring water environmental security in the Jiang-huai region. In this study, we selected the Yangtze-Chao section and Yangtze-Huai section in the water diversion project from the Yangtze River to Huaihe River (Anhui section), systematically analysed the source, composition and distribution characteristics of dissolved organic matter (DOM) and its influencing factors in the water diversion project (Anhui section) from the Yangtze River to Huaihe River at the different hydrological periods from December 2023 to June 2024. The results show as follows: (1) the concentration of total nitrogen (TN), ammonia nitrogen and permanganate index (CODMn) in the water bodies during the different hydrological periods showed increasing trends in the dry season, wet season and normal flow season, and their concentrations decreased after water diversion, especially in the Yangtze-Huai section the concentration of TN decreasing from 4.00±1.45 mg/L to 2.06±0.58 mg/L. TP concentration did not change with the spatial and seasonal distributions. DOC concentration showed significant seasonal and spatial variation. During the dry season, the concentrations of DOC in lakes and estuaries were relatively high, while DOC in river section was low. (2) Four DOM fluorescent components were identified, namely marine-derived humus C1, funic acid humic C2, humic acid C3, and tryptophan group proteins C4. DOM was both influenced by autogenic and terrestrial sources. There is no significant seasonal variation in the proportion of autogenic and terrestrial organic matter in the water during different hydrological periods. After water regulation, there is no obvious difference in the spatial distribution characteristics of DOM fluorescence intensity and DOC concentration due to water exchange. (3) TN, CODMn, DO, Chl-a and WT had a significant impact on the composition and concentration of DOM, while the increase of water temperature and DO had a promoting effect on algae growth and degradation of organic matter. The increase of TN concentration led to the eutrophication of water body and the accumulation of DOM. This study evaluated the water environment quality along the Anhui section of the Yangtze-to-Huaihe water diversion project after its initial implementation of water diversion. It reveals the response patterns of DOM in the early stages of inter-basin water transfer and provides a scientific basis for scheduling the water diversion project from a water quality safety perspective.
2026,(3):000-000, DOI: 10.18307/2026.0345
Available online: November 05, 2025
Abstract:
Affected by global climate change and anthropogenic activities, the degree of saltwater intrusion in China tidal river sections has been intensifying, posing a serious threat to the water-using safety and ecological stability in estuarine areas. The need for saltwater intrusion control is becoming increasingly urgent. Based on the finite volume ocean model, a hydrodynamic salinity numerical model of the estuary area was constructed with the downstream reaches of the Min River as the research region. The model simulated the saltwater intrusion scenario under extreme drought events and explored the influence regulation of upstream reservoir scheduling on saltwater intrusion. The results demonstrate that increasing the discharge flow from upstream reservoirs can significantly reduce the degree of saltwater intrusion. Under the ex-tremely drought conditions during the 2022 dry season, an increase of 240% in reservoir discharge could effectively push the saltwater intrusion boundary back to the confluence of the North Channel and the South Channel. When upstream reservoirs discharge was increased at varying gradients, the morphological differences between the North Channel and the South Channel led to uneven flow distribution, thereby differentially affecting saltwater retreat in the two channels. At an 80% increase in upstream discharge, the North Channel exhibited the maximum retreat of the saltwater intrusion front, beyond which the retreat rate diminished with further flow increases. In contrast, the South Channel showed a propor-tional retreat of the saltwater intrusion front with each incremental doubling of upstream discharge. In addition, when the upstream flow increased in a gradient manner, the longitudinal salinity along the lower reach was significantly reduced, with the largest decrease when the flow increased by 80%, and then the decrease became smaller. This study provides guidance and scientific basis for the formulation and implementation of prevention strategies for saltwater intrusion events in tidal rivers.
Affected by global climate change and anthropogenic activities, the degree of saltwater intrusion in China tidal river sections has been intensifying, posing a serious threat to the water-using safety and ecological stability in estuarine areas. The need for saltwater intrusion control is becoming increasingly urgent. Based on the finite volume ocean model, a hydrodynamic salinity numerical model of the estuary area was constructed with the downstream reaches of the Min River as the research region. The model simulated the saltwater intrusion scenario under extreme drought events and explored the influence regulation of upstream reservoir scheduling on saltwater intrusion. The results demonstrate that increasing the discharge flow from upstream reservoirs can significantly reduce the degree of saltwater intrusion. Under the ex-tremely drought conditions during the 2022 dry season, an increase of 240% in reservoir discharge could effectively push the saltwater intrusion boundary back to the confluence of the North Channel and the South Channel. When upstream reservoirs discharge was increased at varying gradients, the morphological differences between the North Channel and the South Channel led to uneven flow distribution, thereby differentially affecting saltwater retreat in the two channels. At an 80% increase in upstream discharge, the North Channel exhibited the maximum retreat of the saltwater intrusion front, beyond which the retreat rate diminished with further flow increases. In contrast, the South Channel showed a propor-tional retreat of the saltwater intrusion front with each incremental doubling of upstream discharge. In addition, when the upstream flow increased in a gradient manner, the longitudinal salinity along the lower reach was significantly reduced, with the largest decrease when the flow increased by 80%, and then the decrease became smaller. This study provides guidance and scientific basis for the formulation and implementation of prevention strategies for saltwater intrusion events in tidal rivers.
2026,(3):000-000, DOI: 10.18307/2026.0326
Available online: November 05, 2025
Abstract:
Wetlands represent crucial carbon reservoirs within terrestrial ecosystems, functioning as either carbon sources or sinks through complex carbon cycling processes. However, the day-night variations in CO? flux across wetland environments remain inadequately understood, creating uncertainty in accurate assessments of wetland carbon sequestration capacity. This study investigated the temporal dynamics and controlling factors of CO? flux in Poyang Lake wetland during 2021 (a normal flow year), employing eddy covariance measurements with partial correlation and multiple regression analyses during both exposed and inundation periods. The results show that: (1) During the exposed period (January-April and November-December), diurnal CO? flux exhibited characteristic "U"-shaped variations, functioning as a carbon sink during daylight hours and a carbon source at night. Conversely, during the inundation period (May-October), CO? flux remained near zero, though with notable day-night fluctuations emerging during late inundation (September-October). (2) Monthly analyses showed significant day-night CO? flux differences during exposed periods that diminished during inundation, closely corresponding with the transformation between carbon source and sink functions. (3) Annual assessments demonstrated pronounced day-night variations, with average nighttime flux exceeding daytime by 25.5%; this diurnal difference peaked during exposed periods (averaging 10.22 μmol·m?2·s?1). (4) Controlling factors varied by period: during exposed periods, daytime CO2 flux was primarily regulated by incident shortwave radiation and soil moisture, while nighttime CO2 flux was dominated by soil temperature; during inundation, daytime CO2 flux responded mainly to precipitation and soil moisture, while nighttime CO2 flux was jointly influenced by soil moisture, lake water level, and soil temperature. (5) The fundamental mechanisms driving these diurnal differences were period-dependent. During exposed periods, biological processes, including photosynthesis (daytime) and respiration (nighttime), created distinct carbon sink-source dynamics. During inundation, water coverage suppressed both plant and microbial activities, consequently reducing day-night CO2 flux variations. These findings elucidate the diurnal mechanisms governing wetland CO? flux, providing valuable scientific basis for integrated carbon-water resource management and wetland ecological protection.
Wetlands represent crucial carbon reservoirs within terrestrial ecosystems, functioning as either carbon sources or sinks through complex carbon cycling processes. However, the day-night variations in CO? flux across wetland environments remain inadequately understood, creating uncertainty in accurate assessments of wetland carbon sequestration capacity. This study investigated the temporal dynamics and controlling factors of CO? flux in Poyang Lake wetland during 2021 (a normal flow year), employing eddy covariance measurements with partial correlation and multiple regression analyses during both exposed and inundation periods. The results show that: (1) During the exposed period (January-April and November-December), diurnal CO? flux exhibited characteristic "U"-shaped variations, functioning as a carbon sink during daylight hours and a carbon source at night. Conversely, during the inundation period (May-October), CO? flux remained near zero, though with notable day-night fluctuations emerging during late inundation (September-October). (2) Monthly analyses showed significant day-night CO? flux differences during exposed periods that diminished during inundation, closely corresponding with the transformation between carbon source and sink functions. (3) Annual assessments demonstrated pronounced day-night variations, with average nighttime flux exceeding daytime by 25.5%; this diurnal difference peaked during exposed periods (averaging 10.22 μmol·m?2·s?1). (4) Controlling factors varied by period: during exposed periods, daytime CO2 flux was primarily regulated by incident shortwave radiation and soil moisture, while nighttime CO2 flux was dominated by soil temperature; during inundation, daytime CO2 flux responded mainly to precipitation and soil moisture, while nighttime CO2 flux was jointly influenced by soil moisture, lake water level, and soil temperature. (5) The fundamental mechanisms driving these diurnal differences were period-dependent. During exposed periods, biological processes, including photosynthesis (daytime) and respiration (nighttime), created distinct carbon sink-source dynamics. During inundation, water coverage suppressed both plant and microbial activities, consequently reducing day-night CO2 flux variations. These findings elucidate the diurnal mechanisms governing wetland CO? flux, providing valuable scientific basis for integrated carbon-water resource management and wetland ecological protection.
2026,(3):000-000, DOI: 10.18307/2026.0302
Available online: November 05, 2025
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 1,000 kilometers in length. With more than 90,000 water reservoirs, China ranked the 1st 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 cyclings of elements, global climate change, etc. Reservoirs alter sediment microbial communities not only via the changes of a variety of physical, chemical, 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 the 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 1,000 kilometers in length. With more than 90,000 water reservoirs, China ranked the 1st 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 cyclings of elements, global climate change, etc. Reservoirs alter sediment microbial communities not only via the changes of a variety of physical, chemical, 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 the 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.
2026,(3):000-000, DOI: 10.18307/2026.0353
Available online: November 04, 2025
Abstract:
Under the combined pressures of climate change and human activities, lake ecosystems across different regions of the Poyang Lake Basin have experienced varying degrees of degradation. A deep understanding of the long-term evolution and pattern of the lake basin environment is of great significance for the ecological restoration and conservation of Poyang Lake. Based on 21?Pb dating, this study employs a multi-proxy analysis including total organic carbon (TOC), total nitrogen (TN), their molar ratio (C/N ratio), organic carbon accumulation rate (OCAR), total nitrogen accumulation rate (TNAR), and stable carbon isotope of organic matter (δ13C??g) in sediments from Junshan Lake and Qinglan Lake in the southern Poyang Lake basin. It reveals the main sources of sedimentary organic matter and potential mechanisms driving changes in lake primary productivity and eutrophication processes over the past century. The results indicate that the C/N ratios and δ13C??g values in Junshan Lake ranged from 7.7 – 10.5 and -23.9‰ to -22.0‰, respectively, while in Qinglan Lake they ranged from 8.7 – 11.3 and -26.3‰ to -21.7‰. This suggests that sedimentary organic matter in both lakes primarily originated from macrophytes (large aquatic plants) and phytoplankton. Post-1905 in Junshan Lake and post-1980 in Qinglan Lake, TOC and TN concentrations showed an increasing trend, reflecting a common characteristic of gradually rising lake primary productivity. The differences in the response of δ13Corg to changes in primary productivity of different types of lakes reflected the differences in the composition of aquatic plant communities. Specifically, Junshan Lake, primarily influenced by climate warming and aquaculture activities, has undergone a successional shift over the past two centuries: from macrophyte dominance, through a phase of macrophyte-algae codominance, to the current state of algal dominance. In contrast, Qinglan Lake experienced a decline in submerged vegetation following the diversion of the river in 1958, largely due to increased sediment input. After 1980, superimposed impacts from domestic sewage and agricultural non-point source pollution associated with urbanization further accelerated this trend. Consequently, phytoplankton has become the dominant source of sedimentary organic matter in Qinglan Lake. Furthermore, this study compares the ecological environment evolution in different sub-regions of Poyang Lake, providing a scientific basis for understanding their divergent characteristics and clarifying the mechanisms of ecological degradation driven by the coupling of multiple factors.
Under the combined pressures of climate change and human activities, lake ecosystems across different regions of the Poyang Lake Basin have experienced varying degrees of degradation. A deep understanding of the long-term evolution and pattern of the lake basin environment is of great significance for the ecological restoration and conservation of Poyang Lake. Based on 21?Pb dating, this study employs a multi-proxy analysis including total organic carbon (TOC), total nitrogen (TN), their molar ratio (C/N ratio), organic carbon accumulation rate (OCAR), total nitrogen accumulation rate (TNAR), and stable carbon isotope of organic matter (δ13C??g) in sediments from Junshan Lake and Qinglan Lake in the southern Poyang Lake basin. It reveals the main sources of sedimentary organic matter and potential mechanisms driving changes in lake primary productivity and eutrophication processes over the past century. The results indicate that the C/N ratios and δ13C??g values in Junshan Lake ranged from 7.7 – 10.5 and -23.9‰ to -22.0‰, respectively, while in Qinglan Lake they ranged from 8.7 – 11.3 and -26.3‰ to -21.7‰. This suggests that sedimentary organic matter in both lakes primarily originated from macrophytes (large aquatic plants) and phytoplankton. Post-1905 in Junshan Lake and post-1980 in Qinglan Lake, TOC and TN concentrations showed an increasing trend, reflecting a common characteristic of gradually rising lake primary productivity. The differences in the response of δ13Corg to changes in primary productivity of different types of lakes reflected the differences in the composition of aquatic plant communities. Specifically, Junshan Lake, primarily influenced by climate warming and aquaculture activities, has undergone a successional shift over the past two centuries: from macrophyte dominance, through a phase of macrophyte-algae codominance, to the current state of algal dominance. In contrast, Qinglan Lake experienced a decline in submerged vegetation following the diversion of the river in 1958, largely due to increased sediment input. After 1980, superimposed impacts from domestic sewage and agricultural non-point source pollution associated with urbanization further accelerated this trend. Consequently, phytoplankton has become the dominant source of sedimentary organic matter in Qinglan Lake. Furthermore, this study compares the ecological environment evolution in different sub-regions of Poyang Lake, providing a scientific basis for understanding their divergent characteristics and clarifying the mechanisms of ecological degradation driven by the coupling of multiple factors.
2026,(3):000-000, DOI: 10.18307/2026.0323
Available online: November 04, 2025
Abstract:
The numerous lakes distributed in Inner Mongolia have experienced problems of excessive fluoride concentration due to environmental changes, posing carcinogenic health risks to humans and the lakes themselves, as well as potential ecological risks. To deeply explore the characteristics of fluoride forms in lake sediments and reveal the response relationship between fluoride adsorption-desorption behavior and influencing factors, Daihai Lake was selected as the research object. Surface sediment samples were collected, and the contents of different forms of fluoride were detected through multi-stage extraction. ArcGIS software was used to analyze the temporal and spatial differences of fluoride. Further, a 4-factor, 3-level orthogonal simulation experiment of fluoride adsorption-desorption in sediments and a simulation experiment of adsorption-desorption kinetics model were designed to reveal the influence of environmental factors on the adsorption and desorption behavior of fluoride in cold and arid lake sediments. The results showed that the average total fluoride content in the sediments of Daihai Lake was 860.44 ± 53.64 mg·kg-1, with a range of 600.03 to 1388.67 mg·kg-1. Among them, the content ranges of water-soluble, exchangeable, iron-manganese-bound, and organic-bound fluoride were 29.51 to 42.87 mg·kg-1, 8.37 to 21.81 mg·kg-1, 2.46 to 7.21 mg·kg-1, and 9.79 to 17.59 mg·kg-1, respectively. The fitting analysis of the fluoride adsorption-desorption process in sediments indicated that the pseudo-second-order kinetic model had a higher fitting degree under different initial concentrations and could better describe the kinetic process of this adsorption system. The Langmuir and Freundlich thermodynamic models were used to fit and analyze the fluoride adsorption behavior, confirming that monolayer adsorption played a key role in the adsorption process, while multilayer adsorption on heterogeneous surfaces was also an important factor affecting the adsorption behavior. Through the range analysis and variance analysis of orthogonal experimental data, the influence degree and significance of each environmental factor on the adsorption effect were determined. Among them, temperature was the core driving factor for fluoride adsorption-desorption (ANOVA significance: temperature > initial concentration > disturbance intensity > pH). The optimal conditions were screened out based on k values: initial concentration of 10 mg·L-1, temperature of 20 ℃, pH of 7, and shaking frequency of 200 r·min-1. This study can provide important theoretical support for the prevention and control of fluoride release pollution from lake sediments in cold and arid regions.
The numerous lakes distributed in Inner Mongolia have experienced problems of excessive fluoride concentration due to environmental changes, posing carcinogenic health risks to humans and the lakes themselves, as well as potential ecological risks. To deeply explore the characteristics of fluoride forms in lake sediments and reveal the response relationship between fluoride adsorption-desorption behavior and influencing factors, Daihai Lake was selected as the research object. Surface sediment samples were collected, and the contents of different forms of fluoride were detected through multi-stage extraction. ArcGIS software was used to analyze the temporal and spatial differences of fluoride. Further, a 4-factor, 3-level orthogonal simulation experiment of fluoride adsorption-desorption in sediments and a simulation experiment of adsorption-desorption kinetics model were designed to reveal the influence of environmental factors on the adsorption and desorption behavior of fluoride in cold and arid lake sediments. The results showed that the average total fluoride content in the sediments of Daihai Lake was 860.44 ± 53.64 mg·kg-1, with a range of 600.03 to 1388.67 mg·kg-1. Among them, the content ranges of water-soluble, exchangeable, iron-manganese-bound, and organic-bound fluoride were 29.51 to 42.87 mg·kg-1, 8.37 to 21.81 mg·kg-1, 2.46 to 7.21 mg·kg-1, and 9.79 to 17.59 mg·kg-1, respectively. The fitting analysis of the fluoride adsorption-desorption process in sediments indicated that the pseudo-second-order kinetic model had a higher fitting degree under different initial concentrations and could better describe the kinetic process of this adsorption system. The Langmuir and Freundlich thermodynamic models were used to fit and analyze the fluoride adsorption behavior, confirming that monolayer adsorption played a key role in the adsorption process, while multilayer adsorption on heterogeneous surfaces was also an important factor affecting the adsorption behavior. Through the range analysis and variance analysis of orthogonal experimental data, the influence degree and significance of each environmental factor on the adsorption effect were determined. Among them, temperature was the core driving factor for fluoride adsorption-desorption (ANOVA significance: temperature > initial concentration > disturbance intensity > pH). The optimal conditions were screened out based on k values: initial concentration of 10 mg·L-1, temperature of 20 ℃, pH of 7, and shaking frequency of 200 r·min-1. This study can provide important theoretical support for the prevention and control of fluoride release pollution from lake sediments in cold and arid regions.
Zhou Bingqian, Zhang Xiaonan, Zhang Can, Niu Haoge, Niu Tingyu, Leng Mingrui, Zhao Xiangyu, Wang Qirui, He Xin, Yang Xiaoyi, Chen Liang, Zhang Hucai
2026,(3):000-000, DOI: 10.18307/2026.0317
Available online: November 03, 2025
Abstract:
Lake Dian, a typical plateau freshwater lake in China, has experienced increasingly severe eutrophication in recent years due to intensified human activities and continuous nutrient inputs. To elucidate the composition and sources of sterols in surface sediments of Lake Dian , this study conducted systematic multi-site sampling and analyzed the spatial distribution of sterol molecular markers, total organic carbon (TOC), total nitrogen (TN), and the C/N ratio, in conjunction with watershed land use patterns. The results revealed pronounced spatial heterogeneity in organic matter content and C/N ratios across the lake. The Caohai area, influenced by urban runoff and multiple river inflows, exhibited higher organic matter content and C/N values compared to Waihai, displaying a southwest-high, northeast-low gradient. In Waihai, deep central zones had greater organic matter content and C/N ratios than littoral shallow areas, forming a center-high, margin-low pattern. Sterol biomarker analysis indicated that C27 sterols (coprostanol, epicoprostanol, cholesterol, and cholestanol) were primarily enriched in Caohai and the northern and southeastern Waihai, reflecting significant inputs from domestic sewage and anthropogenic activities, C?? sterols, including coprostanol and epicoprostanol, were mainly distributed in Caohai, as well as in the northeastern and southern regions of Waihai, indicating strong influence from domestic sewage inputs. C28 and C29 sterols (campesterol, stigmasterol, and β-sitosterol) were enriched in Caohai as well as in the central and southern regions of Waihai,, indicating substantial higher plant inputs associated with intensive agricultural activity. C30 sterol (dinosterol) was notably elevated in the southern sediments, suggesting high dinoflagellate biomass. Overall, the integration of sterols with TOC, TN, C/N ratios, and land use analysis effectively reveals the spatial heterogeneity of autochthonous, allochthonous, and anthropogenic organic matter in Lake Dian sediments, providing a robust tool for eutrophication monitoring and pollution source apportionment in plateau lake systems.
Lake Dian, a typical plateau freshwater lake in China, has experienced increasingly severe eutrophication in recent years due to intensified human activities and continuous nutrient inputs. To elucidate the composition and sources of sterols in surface sediments of Lake Dian , this study conducted systematic multi-site sampling and analyzed the spatial distribution of sterol molecular markers, total organic carbon (TOC), total nitrogen (TN), and the C/N ratio, in conjunction with watershed land use patterns. The results revealed pronounced spatial heterogeneity in organic matter content and C/N ratios across the lake. The Caohai area, influenced by urban runoff and multiple river inflows, exhibited higher organic matter content and C/N values compared to Waihai, displaying a southwest-high, northeast-low gradient. In Waihai, deep central zones had greater organic matter content and C/N ratios than littoral shallow areas, forming a center-high, margin-low pattern. Sterol biomarker analysis indicated that C27 sterols (coprostanol, epicoprostanol, cholesterol, and cholestanol) were primarily enriched in Caohai and the northern and southeastern Waihai, reflecting significant inputs from domestic sewage and anthropogenic activities, C?? sterols, including coprostanol and epicoprostanol, were mainly distributed in Caohai, as well as in the northeastern and southern regions of Waihai, indicating strong influence from domestic sewage inputs. C28 and C29 sterols (campesterol, stigmasterol, and β-sitosterol) were enriched in Caohai as well as in the central and southern regions of Waihai,, indicating substantial higher plant inputs associated with intensive agricultural activity. C30 sterol (dinosterol) was notably elevated in the southern sediments, suggesting high dinoflagellate biomass. Overall, the integration of sterols with TOC, TN, C/N ratios, and land use analysis effectively reveals the spatial heterogeneity of autochthonous, allochthonous, and anthropogenic organic matter in Lake Dian sediments, providing a robust tool for eutrophication monitoring and pollution source apportionment in plateau lake systems.
Li Xingyue, Liu Xiaomin, Liu Tingxi, Zhang Sheng, Lu Zongfu, Wang Wenjuan, Wang Zihang, Yang Yaotian
2026,(3):000-000, DOI: 10.18307/2026.0311
Available online: November 03, 2025
Abstract:
Under the conditions of climate warming and water eutrophication, cyanobacteria blooms frequently broke out in Hulun Lake in 2022, covering almost the entire lake surface, destroying the water landscape and seriously threatening the health and safety of the lake ecosystem. In order to reveal the driving mechanism of large-scale outbreak of cyanobacteria in Hulun Lake, 13 sampling sites were selected to collect surface, middle and bottom water samples in spring, summer and autumn of 2022, and the species, cell density, biomass and water quality indexes of cyanobacteria were studied. The results showed that a total of 22 species of cyanobacteria were identified, and a total of 10 dominant species were identified, among which Microcystis sp. was the dominant species throughout the survey period. There were significant changes in the density and biomass of cyanobacteria in different periods and depths. The density (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 density 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. The results of correlation analysis and redundancy analysis showed that there were seasonal differences in the influencing factors of cyanobacteria. Water temperature, nitrogen and phosphorus content, dissolved oxygen and pH were the key environmental factors affecting the occurrence of cyanobacterial blooms. In terms of control strategies, moderate control of nutrient content, implementation of nitrogen and phosphorus dual control, and improvement of cyanobacterial bloom prediction and early warning and emergency response capabilities are the fundamental ways to effectively reduce the risk of cyanobacterial blooms, which is of great significance for the prevention and control of cyanobacterial blooms in eutrophic lakes in the future.
Under the conditions of climate warming and water eutrophication, cyanobacteria blooms frequently broke out in Hulun Lake in 2022, covering almost the entire lake surface, destroying the water landscape and seriously threatening the health and safety of the lake ecosystem. In order to reveal the driving mechanism of large-scale outbreak of cyanobacteria in Hulun Lake, 13 sampling sites were selected to collect surface, middle and bottom water samples in spring, summer and autumn of 2022, and the species, cell density, biomass and water quality indexes of cyanobacteria were studied. The results showed that a total of 22 species of cyanobacteria were identified, and a total of 10 dominant species were identified, among which Microcystis sp. was the dominant species throughout the survey period. There were significant changes in the density and biomass of cyanobacteria in different periods and depths. The density (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 density 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. The results of correlation analysis and redundancy analysis showed that there were seasonal differences in the influencing factors of cyanobacteria. Water temperature, nitrogen and phosphorus content, dissolved oxygen and pH were the key environmental factors affecting the occurrence of cyanobacterial blooms. In terms of control strategies, moderate control of nutrient content, implementation of nitrogen and phosphorus dual control, and improvement of cyanobacterial bloom prediction and early warning and emergency response capabilities are the fundamental ways to effectively reduce the risk of cyanobacterial blooms, which is of great significance for the prevention and control of cyanobacterial blooms in eutrophic lakes in the future.
2026,(3):000-000, DOI: 10.18307/2026.0316
Available online: October 31, 2025
Abstract:
Phytoplankton chlorophyll-a (Chl-a) concentration serves as a crucial indicator for assessing water eutrophication status. Conventional monitoring approaches face significant limitations: laboratory analyses are time-consuming and labor-intensive, while in-situ sensors suffer from biofouling interference, low accuracy, and high maintenance costs. Traditional satellite remote sensing techniques are unsuitable for high-precision and real-time monitoring due to incorrect atmospheric correction, technical complexity, and poor temporal resolution. The emergence of hyperspectral proximal sensing technology has effectively addressed these challenges, significantly improving Chl-a concentration monitoring efficiency. This study employed a novel portable hyperspectral proximal sensing water quality monitoring device, collecting 533 synchronized in-situ Chl-a measurements across eight lakes, reservoirs, and rivers from 2021 to 2024. High-accuracy Chl-a concentration inversion models were developed and compared through both linear regression algorithms and machine learning approaches to achieve real-time Chl-a concentration monitoring. Comparative analysis of models based on linear regression, Random Forest (RF), Extreme Gradient Boosting (XGBoost), and Support Vector Machine (SVM) algorithms revealed that the XGBoost-based model demonstrated superior performance (R2=0.87, RMSE=6.02 μg/L, MAE=3.98 μg/L). This innovative methodology enables simultaneous spectral acquisition and Chl-a concentration estimation, streamlining field monitoring procedures while reducing technical barriers and significantly enhancing operational efficiency.
Phytoplankton chlorophyll-a (Chl-a) concentration serves as a crucial indicator for assessing water eutrophication status. Conventional monitoring approaches face significant limitations: laboratory analyses are time-consuming and labor-intensive, while in-situ sensors suffer from biofouling interference, low accuracy, and high maintenance costs. Traditional satellite remote sensing techniques are unsuitable for high-precision and real-time monitoring due to incorrect atmospheric correction, technical complexity, and poor temporal resolution. The emergence of hyperspectral proximal sensing technology has effectively addressed these challenges, significantly improving Chl-a concentration monitoring efficiency. This study employed a novel portable hyperspectral proximal sensing water quality monitoring device, collecting 533 synchronized in-situ Chl-a measurements across eight lakes, reservoirs, and rivers from 2021 to 2024. High-accuracy Chl-a concentration inversion models were developed and compared through both linear regression algorithms and machine learning approaches to achieve real-time Chl-a concentration monitoring. Comparative analysis of models based on linear regression, Random Forest (RF), Extreme Gradient Boosting (XGBoost), and Support Vector Machine (SVM) algorithms revealed that the XGBoost-based model demonstrated superior performance (R2=0.87, RMSE=6.02 μg/L, MAE=3.98 μg/L). This innovative methodology enables simultaneous spectral acquisition and Chl-a concentration estimation, streamlining field monitoring procedures while reducing technical barriers and significantly enhancing operational efficiency.
wangcong, wangzhi, lienhua, zhanglu, liuxi, lishuyin, liruiwen, xingpeng, aosicheng, lushaoyong, tantiejun, yangjun
2026,(3):000-000, DOI: 10.18307/2026.0301
Available online: October 31, 2025
Abstract:
The lack of freshwater ecosystem damage assessment system seriously hinders the implementation of environmental justice and ecological compensation in China. To address this gap, we developed a comprehensive freshwater ecosystem damage assessment system, guided by national standards for ecological environment damage assessment and the practical needs of environmental protection public interest litigation. The system encompasses three dimensions, including environmental quality, biological integrity and ecological function, and is structured into 1 target, 2 sub-targets, 8 criteria, and 27 indicators. In this system, the ecological baseline of the indicators is calculated by the trisection method and the quartile method, and hierarchical calculation formulas from the indicator to the target were provided. The degree of ecosystem damage is measured by the ecological damage index (EDI), with threshold values of 1.2, 1.5, and 2.0 representing mild, moderate, and severe damage, respectively. To validate the system’s applicability, case studies were conducted on Honghu Lake and a river in Xianning. To further improve the effectiveness of the system, the sensitivity and evaluation accuracy of the criterion factors was analyzed. Ensuring evaluation accuracy, we developed a prioritized combination list of assessment criteria (R2 > 0.9, RMSE < 0.1). Subsequently, non-core indicators in the same criterions were removed through correlation analysis. Finally, a prioritized combination list of 1 to 4 levels was provided, including 8, 7, 6, and 5 criteria, respectively, covering 14 to 21 indicators. The construction and application of this freshwater ecosystem damage assessment system not only advance the development of water ecological damage assessment theory in China, but also provide robust theoretical and methodological support for ecological environment protection law enforcement and ecological compensation practices.
The lack of freshwater ecosystem damage assessment system seriously hinders the implementation of environmental justice and ecological compensation in China. To address this gap, we developed a comprehensive freshwater ecosystem damage assessment system, guided by national standards for ecological environment damage assessment and the practical needs of environmental protection public interest litigation. The system encompasses three dimensions, including environmental quality, biological integrity and ecological function, and is structured into 1 target, 2 sub-targets, 8 criteria, and 27 indicators. In this system, the ecological baseline of the indicators is calculated by the trisection method and the quartile method, and hierarchical calculation formulas from the indicator to the target were provided. The degree of ecosystem damage is measured by the ecological damage index (EDI), with threshold values of 1.2, 1.5, and 2.0 representing mild, moderate, and severe damage, respectively. To validate the system’s applicability, case studies were conducted on Honghu Lake and a river in Xianning. To further improve the effectiveness of the system, the sensitivity and evaluation accuracy of the criterion factors was analyzed. Ensuring evaluation accuracy, we developed a prioritized combination list of assessment criteria (R2 > 0.9, RMSE < 0.1). Subsequently, non-core indicators in the same criterions were removed through correlation analysis. Finally, a prioritized combination list of 1 to 4 levels was provided, including 8, 7, 6, and 5 criteria, respectively, covering 14 to 21 indicators. The construction and application of this freshwater ecosystem damage assessment system not only advance the development of water ecological damage assessment theory in China, but also provide robust theoretical and methodological support for ecological environment protection law enforcement and ecological compensation practices.
2026,(3):000-000, DOI: 10.18307/2026.0334
Available online: October 31, 2025
Abstract:
Rapid and accurate monitoring of aquatic vegetation is crucial for the protection and management of lake ecosystems. In this study, the Nanji Wetland National Nature Reserve and Poyang Lake National Nature Reserve were selected as study areas.First,the Normalized Difference Vegetation Index(NDVI) was used to separate water bodies,Then, the Normalized Difference Mud Index(NDMI) was constructed to eliminate the interfernce of mudflats on vegetation classification.Next,floating-leaved plants and emergent plants are distinguished based on differences in the backscattering coefficient within the radar imagery.Finally, this study compared the proposed method with existing methods for distinguishing these two types of aquatic vegetation. The results show that:(1) The method based on backscattering coefficients for distinguishing floating-leaved plants from emergent plants achieved a significant improvement in overall accuracy compared to existing methods. The overall classification accuracy of this method was 89.72%, with a Kappa coefficient of 0.8413.(2) For remote sensing images from different periods, the overall classification accuracy of our method was consistently above 80%, demonstrating good stability and reliability.(3) Our method effectively excluded the interference of mudflats on vegetation classification, thereby avoiding the misclassification of exposed mudflats after water recession. It is particularly suitable for floodplain wetlands with large water level fluctuations.In summary,the method developed in this study provides a new technical approach for distinguishing between floating-leaved and emergent plants and offers a reference for monitoring different types of aquatic vegetation.
Rapid and accurate monitoring of aquatic vegetation is crucial for the protection and management of lake ecosystems. In this study, the Nanji Wetland National Nature Reserve and Poyang Lake National Nature Reserve were selected as study areas.First,the Normalized Difference Vegetation Index(NDVI) was used to separate water bodies,Then, the Normalized Difference Mud Index(NDMI) was constructed to eliminate the interfernce of mudflats on vegetation classification.Next,floating-leaved plants and emergent plants are distinguished based on differences in the backscattering coefficient within the radar imagery.Finally, this study compared the proposed method with existing methods for distinguishing these two types of aquatic vegetation. The results show that:(1) The method based on backscattering coefficients for distinguishing floating-leaved plants from emergent plants achieved a significant improvement in overall accuracy compared to existing methods. The overall classification accuracy of this method was 89.72%, with a Kappa coefficient of 0.8413.(2) For remote sensing images from different periods, the overall classification accuracy of our method was consistently above 80%, demonstrating good stability and reliability.(3) Our method effectively excluded the interference of mudflats on vegetation classification, thereby avoiding the misclassification of exposed mudflats after water recession. It is particularly suitable for floodplain wetlands with large water level fluctuations.In summary,the method developed in this study provides a new technical approach for distinguishing between floating-leaved and emergent plants and offers a reference for monitoring different types of aquatic vegetation.
2026,(3):000-000, DOI: 10.18307/2026.0325
Available online: October 31, 2025
Abstract:
Research on carbon dynamics and source processes in terminal lakes contributes to a precise characterization of their role as "sources" or "sinks" in the regional carbon cycle. This study selected Lake Ulansuhai, a terminal lake in northern China, as the research object. Using methods such as the Bayesian mixing model (MixSIAR) and a carbon isotope two-end-member mixing model, the sources of different forms of carbon in the water body and their main influencing factors were investigated. The main results are as follows: Both dissolved organic carbon (DOC) and particulate organic carbon (POC) showed a spatially decreasing concentration trend from north to south (p<0.05). In April, the primary source of both DOC and POC was phytoplankton, whereas in July and October, the main source was irrigation return flow. For DOC, the overall source contribution proportions were irrigation return flow (72%) > phytoplankton (15%) > terrestrial C3 plants (7%) > aquatic plants (6%). For POC, the overall proportions were phytoplankton (39%) > irrigation return flow (34%) > aquatic plants (15%) > terrestrial C3 plants (12%). Spatially, no significant differences were found for dissolved inorganic carbon (DIC) and particulate inorganic carbon (PIC) (p>0.05). The sources of DIC varied significantly across months: in April, it was primarily contributed by soil organic matter (92.7%) and atmospheric exchange (7.3%); in July, the main sources were irrigation return flow (74.1%) and biological activity (25.9%); in October, the main sources were irrigation return flow (71.9%) and atmospheric exchange (28.1%). PIC mainly originated from endogenous autogenic precipitation. Multiple regression analysis indicated that Chl-a and TN are the main drivers of DOC concentration (R2=0.662, p<0.001); SD, TN, and SPM collectively explained the variation in POC concentration (R2=0.566, p<0.05); NH4+-N is the core regulating factor for DIC concentration (R2=0.370, p<0.001); and both TN and pH have a dual promoting effect on PIC formation (R2=0.573, p<0.05). The findings of this study can provide a scientific basis for carbon cycle research in terminal lakes within agricultural irrigation areas.
Research on carbon dynamics and source processes in terminal lakes contributes to a precise characterization of their role as "sources" or "sinks" in the regional carbon cycle. This study selected Lake Ulansuhai, a terminal lake in northern China, as the research object. Using methods such as the Bayesian mixing model (MixSIAR) and a carbon isotope two-end-member mixing model, the sources of different forms of carbon in the water body and their main influencing factors were investigated. The main results are as follows: Both dissolved organic carbon (DOC) and particulate organic carbon (POC) showed a spatially decreasing concentration trend from north to south (p<0.05). In April, the primary source of both DOC and POC was phytoplankton, whereas in July and October, the main source was irrigation return flow. For DOC, the overall source contribution proportions were irrigation return flow (72%) > phytoplankton (15%) > terrestrial C3 plants (7%) > aquatic plants (6%). For POC, the overall proportions were phytoplankton (39%) > irrigation return flow (34%) > aquatic plants (15%) > terrestrial C3 plants (12%). Spatially, no significant differences were found for dissolved inorganic carbon (DIC) and particulate inorganic carbon (PIC) (p>0.05). The sources of DIC varied significantly across months: in April, it was primarily contributed by soil organic matter (92.7%) and atmospheric exchange (7.3%); in July, the main sources were irrigation return flow (74.1%) and biological activity (25.9%); in October, the main sources were irrigation return flow (71.9%) and atmospheric exchange (28.1%). PIC mainly originated from endogenous autogenic precipitation. Multiple regression analysis indicated that Chl-a and TN are the main drivers of DOC concentration (R2=0.662, p<0.001); SD, TN, and SPM collectively explained the variation in POC concentration (R2=0.566, p<0.05); NH4+-N is the core regulating factor for DIC concentration (R2=0.370, p<0.001); and both TN and pH have a dual promoting effect on PIC formation (R2=0.573, p<0.05). The findings of this study can provide a scientific basis for carbon cycle research in terminal lakes within agricultural irrigation areas.
2026,(3):000-000, DOI: 10.18307/2026.0331
Available online: October 29, 2025
Abstract:
Comprehensive acquisition of aquatic organism data is fundamental for the effective conservation and restoration of aquatic ecosystems. However, efficient monitoring of aquatic biodiversity dynamics in large river systems remains highly challenging. Environmental DNA (eDNA) technology, as an emerging monitoring approach, offers advantages of rapidity and high efficiency. Nevertheless, conventional cross-sectional small-volume eDNA sampling methods exhibit clear limitations in detecting rare fish species. To address this issue, the present study developed a novel mobile large-volume eDNA sampling method, which substantially increases the water volume filtered per sample through the use of capsule filtration and integrates a mobile sampling strategy to improve the efficiency and representativeness of eDNA metabarcoding surveys. In October 2022, comparative surveys were conducted at two representative cross-sections of the lower Yangtze River to evaluate differences in fish diversity detection between the mobile large-volume method and the conventional small-volume cross-sectional method. All eDNA samples were amplified and sequenced using the Tele02 primer set. The results demonstrated that: (1) Each large-volume mobile sample detected an average of 38 fish species, representing a 216.7% increase compared with the small-volume cross-sectional method (12 species); (2) The mobile large-volume method exhibited higher accuracy in biodiversity detection and greater consistency among parallel replicates; (3) The mobile large-volume sampling method detected 24 fish species of primary concern, including rare and endangered species listed in the IUCN Red List of Threatened Species, fish species listed in the Catalogue of National Key Protected Economic Aquatic Animals and Plants of China, and Chinese endemic species. This represents a 50% increase compared with the 16 species detected by the cross-sectional small-volume sampling method, with 14 species shared between the two approaches. Overall, the study confirms that the mobile large-volume eDNA sampling method demonstrates significant advantages in species detection rate, detection precision and stability, and the identification of fish species of primary conservation concern in large river systems.
Comprehensive acquisition of aquatic organism data is fundamental for the effective conservation and restoration of aquatic ecosystems. However, efficient monitoring of aquatic biodiversity dynamics in large river systems remains highly challenging. Environmental DNA (eDNA) technology, as an emerging monitoring approach, offers advantages of rapidity and high efficiency. Nevertheless, conventional cross-sectional small-volume eDNA sampling methods exhibit clear limitations in detecting rare fish species. To address this issue, the present study developed a novel mobile large-volume eDNA sampling method, which substantially increases the water volume filtered per sample through the use of capsule filtration and integrates a mobile sampling strategy to improve the efficiency and representativeness of eDNA metabarcoding surveys. In October 2022, comparative surveys were conducted at two representative cross-sections of the lower Yangtze River to evaluate differences in fish diversity detection between the mobile large-volume method and the conventional small-volume cross-sectional method. All eDNA samples were amplified and sequenced using the Tele02 primer set. The results demonstrated that: (1) Each large-volume mobile sample detected an average of 38 fish species, representing a 216.7% increase compared with the small-volume cross-sectional method (12 species); (2) The mobile large-volume method exhibited higher accuracy in biodiversity detection and greater consistency among parallel replicates; (3) The mobile large-volume sampling method detected 24 fish species of primary concern, including rare and endangered species listed in the IUCN Red List of Threatened Species, fish species listed in the Catalogue of National Key Protected Economic Aquatic Animals and Plants of China, and Chinese endemic species. This represents a 50% increase compared with the 16 species detected by the cross-sectional small-volume sampling method, with 14 species shared between the two approaches. Overall, the study confirms that the mobile large-volume eDNA sampling method demonstrates significant advantages in species detection rate, detection precision and stability, and the identification of fish species of primary conservation concern in large river systems.
2026,(3):000-000, DOI: 10.18307/2026.0315
Available online: October 22, 2025
Abstract:
Carbon sinks of natural ecological systems are regarded as one of the key pathways to combat climate change. Eutrophic lakes, due to their higher primary productivity, have higher carbon sink potential. This study estimated the algae-derived carbon sink in eutrophic Lake Taihu from 2011 to 2020 using the Vertically Generalized Production Model (VGPM), quantified the contribution of key influencing factors using the Generalized Additive Model (GAM), and conducted short-term prediction using the Autoregressive Integrated Moving Average model (ARIMA). The results indicated that, the cumulative algae-derived carbon sink in Lake Taihu reached 3.8 × 106 t from 2011 to 2020, exhibiting remarkable spatiotemporal heterogeneity. The highest carbon sink occurred in 2019 (7.2 × 105 t), and the lowest was in 2011 (1.7 × 105 t); Zhushan Bay had the highest carbon sink (291 g/m2), while Xuhu Bay had the lowest (66 g/m2). Chlorophyll a concentration was identified as the primary factor driving algal-derived carbon sink, accounting for the largest contribution (86.0%), followed by photosynthetically active radiation, suspended matter concentration, and water temperature, with contributions of 13.2%, 4.6%, and 39.3%, respectively. Using only chlorophyll a concentration as a single parameter, the ARIMA model can effectively estimate the algal-derived carbon sink in Lake Taihu. The findings provide important theoretical insights and methodological support for carbon sink assessment in eutrophic lakes. Keywords: Eutrophication, Lake, Algae, Carbon sink, Short-term prediction
Carbon sinks of natural ecological systems are regarded as one of the key pathways to combat climate change. Eutrophic lakes, due to their higher primary productivity, have higher carbon sink potential. This study estimated the algae-derived carbon sink in eutrophic Lake Taihu from 2011 to 2020 using the Vertically Generalized Production Model (VGPM), quantified the contribution of key influencing factors using the Generalized Additive Model (GAM), and conducted short-term prediction using the Autoregressive Integrated Moving Average model (ARIMA). The results indicated that, the cumulative algae-derived carbon sink in Lake Taihu reached 3.8 × 106 t from 2011 to 2020, exhibiting remarkable spatiotemporal heterogeneity. The highest carbon sink occurred in 2019 (7.2 × 105 t), and the lowest was in 2011 (1.7 × 105 t); Zhushan Bay had the highest carbon sink (291 g/m2), while Xuhu Bay had the lowest (66 g/m2). Chlorophyll a concentration was identified as the primary factor driving algal-derived carbon sink, accounting for the largest contribution (86.0%), followed by photosynthetically active radiation, suspended matter concentration, and water temperature, with contributions of 13.2%, 4.6%, and 39.3%, respectively. Using only chlorophyll a concentration as a single parameter, the ARIMA model can effectively estimate the algal-derived carbon sink in Lake Taihu. The findings provide important theoretical insights and methodological support for carbon sink assessment in eutrophic lakes. Keywords: Eutrophication, Lake, Algae, Carbon sink, Short-term prediction
