[Long-term Variation Characteristics of Zooplankton Community Structure in Meiliang Bay, Lake Taihu].

Zooplankton, as an important part of the water food chain, plays an important role in lake ecosystems. It is an important monitoring indicator for water bodies. However, due to the lack of long-term monitoring data of zooplankton community structure, there is a lack of understanding about its long-term characteristics. Based on monthly monitoring data from 1997 to 2017 of Meiliang Bay in Lake Taihu, the long-term trends of zooplankton community structure and its relation to the environment were examined. The results showed that the abundance and biomass of zooplankton in Meiliang Bay significantly decreased from 1997 to 2017 (<0.05). In particular, the abundance and biomass of rotifer and copepod slowly declined, and the abundance of cladocerans fluctuated but its biomass presented a significant decreasing trend (<0.05). The cladocerous biomass contributed the most to the zooplankton biomass in Meiliang Bay. The dominance of smaller cladocerans and copepods increased with decreasing rotifer density, significantly decreasing the average body size of zooplankton (<0.05). This study indicated that zooplankton were becoming smaller, potentially weakening the top-down control on phytoplankton. In addition, zooplankton abundance and biomass showed an upward trend in spring and decreased in autumn and winter, and reached maximum values of 1406.70 ind.·L and 25.64 mg·L, respectively, in September. In the summer, their changes were the opposite. Pearson correlation analysis showed that zooplankton community structure was significantly related to water physical characteristics (alkalinity, electrical conductivity, water depth, suspended substance, and water temperature), chlorophyll a, and nitrogen (<0.05). This indicated that the eutrophication of Meiliang Bay in Lake Taihu had a significant impact on the community structure of zooplankton.