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| 引用本文: | 吴铭杰,许海,詹旭,邱雨,孙宏伟,秦伯强,朱广伟,张运林.蓝藻生长与衰亡对太湖沉积物-上覆水系统CO2和CH4排放通量的影响及其来源途径.湖泊科学,2025,37(2):401-414. DOI:10.18307/2025.0214 |
| Wu Mingjie,Xu Hai,Zhan Xu,Qiu Yu,Sun Hongwei,Qin Boqiang,Zhu Guangwei,Zhang Yunlin.Effects of growth and decline of cyanobacteria on CH4 and CO2 emission fluxes and their source pathways in sediment-water system of Lake Taihu, China. J. Lake Sci.2025,37(2):401-414. DOI:10.18307/2025.0214 |
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| 蓝藻生长与衰亡对太湖沉积物-上覆水系统CO2和CH4排放通量的影响及其来源途径 |
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吴铭杰1，2，许海2，詹旭1，邱雨2，孙宏伟1，2，秦伯强2，朱广伟2，张运林2
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1.江南大学环境与生态学院，无锡 214122 ；2.中国科学院南京地理与湖泊研究所，湖泊与流域水安全全国重点实验室，南京 211135
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| 摘要: |
| 随着气候变化和人类活动的增加，全球湖泊富营养化日趋加重，湖泊中蓝藻水华频繁发生。湖泊作为全球碳循环的热点区域，一方面通过浮游植物光合作用固定大气中的二氧化碳（CO2），另一方面又通过有机物的降解向大气中排放CO2和甲烷（CH4）。目前关于蓝藻水华对湖泊沉积物-上覆水系统中碳的源汇效应的研究主要集中于藻类死亡降解对含碳温室气体排放的影响，但对藻类光合作用固定大气中CO2效应的研究较少，因此蓝藻水华引起的湖泊碳的源汇效应尚不明确。本研究于2023年夏季采集太湖竺山湾的表层沉积物构建沉积物-上覆水系统，添加不同生物量的蓝藻，进行室内恒温水浴培养模拟实验，定期封闭培养柱，采集顶空气体样品，测定气体中CO2和CH4浓度及碳同位素丰度，研究蓝藻生长和衰亡对CO2和CH4产生途径及排放通量的影响。结果表明，蓝藻生长与衰亡阶段分别呈CO2吸收和排放状态，CO2排放通量随初始蓝藻添加量的增加而增加。蓝藻生长阶段CO2排放通量呈负值，藻类固定CO2；蓝藻衰亡阶段CO2排放通量随着蓝藻的死亡分解逐渐增加，在第25天达到稳定。蓝藻生长阶段的CH4排放通量为(0.022±0.011)~(3.159±0.51) μmol/(m2·h)，在第7天达到峰值：蓝藻衰亡阶段的CH4排放通量显著升高，达到(0.219±0.017)~(9.783±0.215) μmol/(m2·h)，并在第20天达到峰值。将CH4换算为CO2当量(CO2-eq)，各处理组总的CO2-eq排放通量在蓝藻生长阶段表现为“碳汇”（-451.82~-113.28 mmol/(m2·h))，而在蓝藻衰亡阶段表现为“碳源”（35.46~196.86 mmol/(m2·h)）。整个实验周期净CO2-eq排放通量为-746.71 mmol/(m2·h)，表现出强烈的碳汇效应。13C-CO2和13C-CH4稳定同位素结果显示，表观分馏因子αC值均小于1.06，表明蓝藻生长和衰亡阶段CH4产生途径以乙酸发酵为主。随着初始蓝藻添加量的增加，αC逐渐减小，表明蓝藻提高了乙酸发酵途径在CH4代谢中的占比。研究结果对于揭示蓝藻水华对富营养化湖泊碳循环与源汇效应的影响机制具有重要科学意义。 |
| 关键词: 甲烷 排放通量 碳同位素 蓝藻水华 太湖 竺山湾 |
| DOI：10.18307/2025.0214 |
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| 基金项目:江苏省科技厅项目（BK20220041）；国家自然科学基金项目(42271126)；中国科学院南京地理与湖泊研究所自主部署科研项目（NIGLAS2022GS03）联合资助 |
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| Effects of growth and decline of cyanobacteria on CH4 and CO2 emission fluxes and their source pathways in sediment-water system of Lake Taihu, China |
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Wu Mingjie1，2，Xu Hai2，Zhan Xu1，Qiu Yu2，Sun Hongwei1，2，Qin Boqiang2，Zhu Guangwei2，Zhang Yunlin2
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1.School of Environment and Ecology, Jiangnan University, Wuxi 214122 , P.R.China ；2.State Key Laboratory of Lake and Watershed Science for Water Security, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 211135 , P.R.China
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| Abstract: |
| With climate change and intensive human activities, eutrophication of global lakes is increasing. Cyanobacteria blooms occur frequently in lakes. Lakes are the hot spots of global carbon cycle. On one hand, carbon dioxide (CO2) is fixed in the atmosphere through photosynthesis of phytoplankton. On the other hand, CO2 and methane (CH4) are emitted into the atmosphere through the degradation of organic matter. Current research on the effect of cyanobacterial bloom on carbon source and sink mainly focused on the effect of algae death and degradation on carbon-containing greenhouse gas emissions. There are few studies on the photosynthetic carbon sequestration effect of algae. Therefore, surface sediments effects of cyanobacterial blooms in lakes are not clear. In this study, surface sediments were collected from Zhushan Bay, Lake Taihu in summer of 2023 to form a sediment-overlying water system. By adding different biomass of cyanobacteria, indoor constant temperature water bath culture simulation experiments were conducted. The concentrations of CO2 and CH4 and the abundance of carbon isotope in the headspace were measured by sampling in the culture columns. Effects of cyanobacterial bloom's growth and decline on CO2 and CH4 production pathways and emission fluxes were studied. The results showed that cyanobacteria growth and decay correspond to CO2 absorption and emission states, respectively. The CO2 emission flux increased with adding of initial cyanobacterial. The CO2 emission flux was negative in the growth stage of cyanobacteria as algae fixed the CO2. CO2 emission flux during the decay stage increased gradually with the death and decomposition of cyanobacteria. It reached to stability on the 25th day. CH4 emission flux in the growth stage was (0.022±0.011)-(3.159±0.51) μmol/(m2·h) reaching its peak on the 7th day. CH4 emissions during the death stage increased significantly, reaching (0.219±0.017)-(9.783±0.215) μmol/(m2·h) with a peak on the 20th day. After converting CH4 to CO2 equivalent (CO2-eq) and summarizing, the total CO2-eq of each group showed as a “carbon sink” (-451.82--113.28 mmol/(m2·h)) during the whole experiment. However, it was a “carbon source” (35.46-196.86 mmol/(m2·h)) during the death stage. The net CO2-eq emission flux during the whole experiment period was -746.71 mmol/(m2·h), the water columns displayed a strong carbon sink effect. The results of 13C-CO2 and 13C-CH4 stable isotopes showed that the apparent fractionation factor αC were less than 1.06. It indicated that acetic acid fermentation was the main pathway of CH4 production in both growth and decay stages of cyanobacteria. αC gradually decreased with the increase of initial cyanobacteria supplement. This result indicated that cyanobacteria increased the proportion of acetic acid fermentation pathway in CH4 metabolism. These findings have important scientific significance in revealing the mechanism of cyanobacterial blooms on carbon cycling and source sink effects in eutrophic lakes. |
| Key words: Methane discharge flux carbon isotope cyanobacteria bloom Lake Taihu Zhushan Bay |
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