Abstract: In order to understand the characteristics of plankton community structure and eutrophication status in Lake Jinhai， beijing after the South-to-North Water Transfer Project, a comprehensive survey of water quality and plankton in Lake Jinhai was conducted in May and September, 2017, May and September, 2018, respectively. The results showed that Lake Jinhai belongs to diatom-cyanobacteria reservoir with CNaⅠ water type. A total of 111 species (varieties) of phytoplankton, including 8 phyla, with an average density of 4.10×106 ind/L, biomass of 6.68 mg/L, diversity index H′(2.94±0.53), evenness J (0.73±0.37) were collected. Ninty-seven species of zooplankton belonging to 56 genera were detected, with an average density of 1453 ind/L, biomass of 0.70 mg/L, diversity index H′(3.07±0.09) and evenness J(0.64±0.08). Four dominant species were Fragilaria acus, Didinium balbianii, Keratella cochlearis and Proales simplex. Twenty-seven functional groups of phytoplankton were divided, and the seasonal variation of representative functional groups from 2017 to 2018 was: spring (D/lM /LO/P/E), autumn (D/T/J/TC/NA), spring (D/P/J/NA), autumn (D/T/NA/S1/N), respectively. The TLI index was 43.57, belonging to the middle trophic type. The fish productivity of Lake Jinhai was 350.3 kg/hm2, and the total fish productivity of Lake Jinhai was 2.3×105 kg.

Key words: Lake Jinhai, plankton, functional group, community structure, eutrophication, fish productivity