作者: Xiao, Qitao; Xu, Xiaofeng; Duan, Hongtao; 等

    内陆湖泊是全球碳循环的重要组成部分，近几十年围绕着湖泊碳源、碳汇的问题展开了诸多研究。在人类活动和气候变暖的双重影响下，湖泊富营养化问题日益突出，但是富营养化湖泊大气CO2源/汇功能的研究存在很大的争议。一方面，富营养化湖泊中因大量浮游植物生长，初级生产力高，湖体CO2吸收能力强，可表现为大气CO2的汇；另一方面，富营养化湖泊中较高的营养盐负荷为生物代谢提供营养物，刺激呼吸作用和增加有机质降解等，促进湖泊CO2的产生，导致湖泊CO2出现过饱和，是大气CO2的源。研究表明，太湖是大气CO2的源，年均CO2排放通量为18.2 mmol m^-2 d^-1。空间尺度上，因受河流外源负荷输入的影响，太湖富营养湖区是CO2的“热点”排放区，其CO2排放量显著高于其他区域（草型湖区和草藻型过渡湖区）。季节尺度上，太湖水体CO2分压（pCO2）及其CO2排放量在夏季蓝藻暴发期间表现出较低的水平，表明蓝藻生长可固定吸收一定量的水体CO2, 但蓝藻固定的CO2量可能要小于外源CO2输入量，导致富营养化湖泊是显著的大气CO2源。另外，太湖CO2排放量具有显著的年际波动，随着流域管控措施的加强，整体上呈现出逐年降低的趋势。上述结果表明，流域管控不仅能提高湖泊水质，还能显著降低富营养化湖泊CO2排放量，未来应该进行更多研究调查湖泊与人类之间和谐关系的潜在机制。 

Inland lakes receive growing attentions on eutrophication and their roles in global carbon cycle. However, understanding how inland lakes contribute to global carbon cycle is seriously hampered due to a shortage of long-term records. This study investigated the carbon dioxide (CO2) flux from the Lake Taihu, a large (2400km2) and shallow (mean depth 1.9m) eutrophic lake in subtropical region, based on a long-term (2000-2015) measurement of the partial pressure of carbon dioxide (pCO2) at high spatiotemporal resolution. We found that the Lake Taihu was a significant source of atmospheric CO2 with an average CO2 emission flux at 18.2±8.4mmolm-2 d-1 (mean±1standard deviation) and a mean annual pCO2 value of 778±169muatm. The highest pCO2 and CO2 flux were observed in eutrophic zone with a high external input of carbon and nutrient, and the lowest in non-eutrophic zones with no direct external input of nutrient and carbon. A substantial seasonal pattern in pCO2 was observed, particularly in eutrophic pelagic area, and was significantly negatively correlated with chlorophyll a. Long-term measurement showed the interannual variation in annual lake CO2 dynamics, which was highly sensitive to human-induced nutrient input. Watershed input of carbon and nutrient leads to the high CO2 level, counterbalancing the in-lake primary production. All lines of evidence suggest that human activities may have predominate contribution to CO2 source in the Lake Taihu, and this mechanism might be widespread in global freshwater lakes.

Water research 卷: 170 页: 115331 出版年: 2019

(中国科学院南京地理与湖泊研究所段洪涛研究员团队，与美国圣地亚哥州立大学徐小锋教授、耶鲁大学李旭辉教授等团队合作，以大型浅水富营养化湖泊-太湖为研究对象，基于太湖湖泊生态系统国家野外观测研究站长时序监测数据（2000-2015），深入剖析了富营养化湖泊CO2的动态变化及其环境驱动机制，最新研究成果发表在Water Research（2020, 170, 115331）)