Community Structures Of Zooplankton And Its Relation To Environmental Factors In Poyang Lake,China

Poyang Lake,located in the north of Jiangxi Province and on the South Bank of the middle and lower reaches of the Yangtze River,is one of the few river lakes in China.Because of its unique hydrological changes,Poyang Lake also plays an important ecological function.However,with the rapid development of city,economy and water conservancy,the water ecological environment of Poyang Lake Basin has gradually deteriorated.Zooplankton,as the primary consumer in the food chain,can further affect the function of aquatic ecosystem through the nutrient cascade of phytoplankton zooplankton fish(P-Z-F).In order to explore the community characteristics of zooplankton(including rotifers,Cladocera and copepods)in Poyang Lake,the largest fresh water lake in China,and their relationship with environmental factors,66 sampling points were set up in Poyang Lake in this study.The zooplankton community and habitat were investigated in August(summer),November(autumn),February(winter)and May(spring)in 2017,and statistical analysis was carried out The results show that:1.During the investigation,112 species of zooplankton belonging to 45 genera were identified in Poyang Lake.The number of zooplankton species in spring and summer is more than that in autumn,and the least in winter.2.The annual average abundance of zooplankton in Poyang Lake is 1155.29 ind./L.the distribution of zooplankton in season and space is mainly rotifer,and the abundance of Cladocera and copepod is very low.The seasonal variation of zooplankton abundance is the highest in summer,the second in autumn and spring,and the lowest in winter.Spatially,zooplankton abundance in each season showed a trend of decreasing from south to north.The annual average biomass of zooplankton in Poyang Lake is 2.01 mg/L.The seasonal and spatial distribution of zooplankton biomass is very significant.The seasonal variation of zooplankton biomass is higher in summer,next in autumn and spring,and lower in winter.Spatially,the zooplankton biomass increased first from south to North and then decreased in each season.The biomass in the area of Jiji Lake(?)was higher than that in the area of Tongjiang Lake(?)and benghukou estuary(?)in the north.3.There are 14 dominant species of zooplankton in Poyang Lake,including 13 species of rotifers,only Daphnia carinata,polyarthra vulgaris.Rotifer,rotifer and rotifer are the dominant species in the whole lake.There are seasonal differences in the composition of dominant species,and the composition of dominant species is the most complex in summer.In autumn,the dominance of the snail rotifer(Keratella cochlearis)is the highest,and the composition of dominant species in winter is relatively simple.4.Shannon Weiner diversity index of zooplankton in Poyang Lake is 1.65 with a range of 0-2.62.The seasonal variation was higher in summer,followed by autumn and spring,and lower in winter.The spatial distribution of Shannon Weiner diversity index is higher in the South than in the north.The annual average value of Pielou evenness index is 0.73,with a range of 0.11-1.The seasonal variation is the highest in winter,followed by autumn and spring,and the lowest in summer.Pielou evenness index has little difference among different regions,and there is no obvious spatial change.5.The results of non metric multidimensional scaling show that temperature,Chla and conductivity are the most important environmental factors that cause significant differences in zooplankton communities in the four seasons.Temperature,chlorophyll a and p H are the main environmental factors that make the community different from other seasons.Conductivity,dissolved oxygen,total nitrogen and total phosphorus are the main factors that affect the community structure of zooplankton in winter.6.Cluster analysis and classification and regression trees show that there are many community types in each season,among which the division of zooplankton community types in spring and summer is closely related to Chla,and chemical oxygen demand is the key environmental factor affecting the community division in autumn.7.The velocity of flow also has some influence on the abundance and species composition of zooplankton.The results of biomass comparison in different flow velocity regions showed that the biomass difference between the low flow velocity region and the middle flow velocity region was small,and the biomass in the high flow velocity region decreased.With the increase of flow velocity,the proportion of zooplankton groups is different.The change of nutrient level and hydrodynamic conditions of the rivers flowing into the lake will also affect the change of zooplankton abundance,and the increase of zooplankton abundance will accelerate when the tributaries with higher nutrient level flow into Poyang Lake.8.The results of variation decomposition showed that the variation of Rotifer Community was mainly explained by environmental factors,spatial factors were the main factors affecting the community differences of crustacean plankton,and the interaction of spatial environment was also significant.The results of redundance analysis and variation decomposition showed that the main influencing factor of Rotifer Community Structure in spring and summer was Chla,and TSS had a great influence on the variation of Rotifer Community Structure in autumn.