A comparison of factors influencing the summer phytoplankton biomass in China's three largest freshwater lakes: Poyang, Dongting, and Taihu

摘要

In this study, a large dataset for the three largest freshwater lakes (Poyang, Dongting, and Taihu) of the Yangtze River floodplain in China was analyzed to quantitatively compare the ecological structure and function of the Yangtze-connected (Poyang and Dongting) and Yangtze-isolated (Taihu) lakes on a broad scale. Discriminant analyses were performed to determine and correlate the composite gradient of physical-chemical variables that separated the six study regions, East Poyang Lake (LPY), Open LPY, North LPY, Dongting, Meiliang Bay, and Taihu center, with variables including suspended solids (SS), Secchi depth (SD), water temperature (WT), chemical oxygen demand (COD), flow velocity, and total nitrogen-to-total phosphorous (TN:TP) molar ratio. A regression analysis showed that the interactions between the SS and TP concentrations affected the phytoplankton biomass in the lentic (Meiliang Bay and East LPY) and partly lotic (Open LPY and Dongting) zones. The trophic level index (TLI)-phytoplankton, SS-phytoplankton, and TP-phytoplankton relationships revealed that hydrological (water velocity) and physical (underwater light penetration) conditions had the greatest effect on the algal biomass in the eutrophic Yangtze-connected lakes, whereas phytoplankton growth was mainly related to nutrients in the eutrophic Yangtze-isolated lake.