The Response Of Zooplankton Community To Water Level Fluctuation In Sub-lakes Of The Poyang Lake

Zooplankton is an important biological component of the aquatic ecosystem that located in the middle of the lake ecosystem food network.It plays an important role in the transformation and transfer of lake primary productivity.The stability of the community is of great significance to the stability and health of the lake ecosystem.Poyang Lake is the largest freshwater lake in China.Affected by the influx of the Five Rivers and the Yangtze River,the wet and dry periods alternate periodically.The complexity of the hydrological conditions has created a complex water ecological environment of Poyang Lake,which makes Poyang Lake's aquatic biodiversity resources abundant.In this study,two sub-lakes of Poyang Lake,Dahuchi Lake and Shahu Lake were taken as research sites to study the dynamic changes of community structure of zooplankton during the drastic changes of water level.The purpose was to understand the process of rapid natural water level fluctuations(July 1,2016 to August 23,2016)and to artificially control water level changes(November 9,2014 to January 4,2015).During the process,the dynamics of zooplankton community structure were analyzed,and the response of the zooplankton to water level changes was analyzed through the analysis of the traits of the dominant species.The study found that the number,density,and biomass of zooplankton in the Dahuchi Lake and Shahu Lakes during the drastic changes in water level all change with the rapid rise and fall of the water level.The number of species of dominant species in the two sub-lakes is relatively small,and the variation in density is quite different.Non-metric multidimensional scaling analysis(NMDS)showed that significant differences in zooplankton community structure during the change of water level(P < 0.05).Redundancy analysis found that the water depth,transparency,temperature and other environmental factors are also important factors affecting the zooplankton community structure.In the process of artificially controlling water level in “Plate-shaped Lake Enclosed in Autumn”,the specie richness and diversity index of zooplankton gradually decreased with the decrease of water level.Zooplankton density and biomass showed that the change tendency increased first and then decreased.The density variation of dominant species in zooplankton has obvious species differences,increase or decrease.In addition,according to the change of fishing catch during“Plate-shaped Lake Enclosed in Autumn”,we proposed that the decrease in planktonic fish caused by fishing activities also resulted in a certain impact on zooplankton density.