Imbalance of plankton community metabolism in eutrophic Lake Taihu, China |
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Authors: | Xia Liu Qinglong WuYuwei Chen Martin T. Dokulil |
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Affiliation: | a School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, Chinab State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, Chinac Institute of Limnology, Austrian Academy of Sciences, 5310 Mondsee, Austria |
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Abstract: | Studies suggest that oligotrophic lakes are net heterotrophic and act as net sources of CO2, whereas eutrophic lakes are net autotrophic and act as net CO2 sinks. Data on plankton community metabolism in Lake Taihu contradict this hypothesis. Here, the ratios of depth integrated gross primary production (GPP) to plankton community respiration (PCR) were less than one on 75% of the study sampling dates, indicating that this system was net heterotrophic. Partial pressure estimated for CO2 also indicated that the lake was a net source of CO2. Net heterotrophic conditions here may be related to limitation of phytoplankton photosynthesis by the poor underwater light climate (due to elevated suspended solids (SS) and nutrients originating in the catchment) and the preferential enhancement of respiration by high water temperatures. GPP and PCR were significantly correlated (PCR = 1.22GPP + 0.46, r2 = 0.80) indicating a partial dependence of heterotrophs on algal derived carbon. The slope of the regression line relating PCR to GPP was more similar to slopes found in rivers than in lakes, likely due to the large nutrient and SS load to the lake. |
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Keywords: | Plankton community respiration Gross primary production Eutrophic |
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