CRUSTACEAN ZOOPLANKTON COMMUNITY IN XIANGXI BAY DURING THE LATER IMPOUNDMENT PERIOD OF THE THREE GORGES RESERVOIR

To understand the community structure, temporal and spatial changes of crustacean zooplankton in Xiangxi Bay of the Three Gorges Reservoir during the later impoundment period, monthly sampling from January 2015 to December 2017 and analysis of crustacean zooplankton in Xiangxi Bay of the Three Gorges Reservoir were conducted. A total of 23 species of crustacean zooplankton were identified, of which 10 species belong to Cladocera, and 13 species belong to Copepoda. Species with a higher frequency are the common species in the Yangtze River Basin. The peaks of biomass and density occurred in May and June, respectively. We did not collect specimens in January and February. The interannual differences in biomass and density vary significantly, and the difference of community composition was not significant. Community seasonal pattern in spring and summer was dominated by large size Cladocera (Daphnia pulex and Daphnia cucullata), and in autumn was dominated by small size Cladocera (Bosmina coregoni). The biodiversity index in the middle reservoir was higher than that of the upper regions and downstream parts. There was no significant difference in biodiversity index between upper regions and downstream parts, and there was also difference in biodiversity index of some seasons. Results from CCA showed that water temperature, chlorophyll concentrate and water depth were important factors explaining the change of crustacean zooplankton community. The results showed that nutrient, water temperature, crustacean zooplankton biomass and density all have not reached a stable state, but the community composition in different years was not significant. The richness of Crustacean zooplankton species was higher than that of early reservoir. The biological diversity index has a certain difference in time and space, and an appropriate degree of interference may help maintain high biodiversity diversity.