Temporal And Spatial Patterns Of Zooplankton Community In Poyang Lake And Its Connected Waters

The floodplain lake is one of the most productive ecosystems in the world,providing basic ecological functions and services for the development of human civilization.The middle and lower reaches of the Yangtze River have numerous lakes and dense river networks.They contain a wide range of flood plains and lakes.They are the rare resource pool of freshwater species in the world and have extremely high biological productivity.Poyang Lake is the largest freshwater lake in China with the Yangtze River.The Yangtze River,Poyang Lake and its five rivers form a complex river-lake-river complex ecosystem.Zooplankton is the main component of freshwater ecosystems.It is small in size and sensitive to changes in water conditions,and plays an important role in maintaining the stability of aquatic ecosystems.In December 2016,June 2017,September 2017 and November 2017,the author surveyed zooplankton in the main lake area of Poyang Lake and its connected rivers,and analyzed the zooplankton in Poyang Lake and its connected waters during different hydrological periods.Differences in community structure,explore the factors that influence the differences,and then clarify the significance of the Yangtze River-Lake(Poyang Lake)-river(enter the lake)connectivity for the conservation of zooplankton diversity.The results can be the Poyang Lake biodiversity.Protection and scientific management of Poyang Lake provide the basis.Below are key research findings.1.126 species of zooplankton were recorded in the main lake area of Poyang Lake and its connected rivers,including 83 species of rotifers,25 species of cladocerans and 18 species of copepods.In terms of seasons,the number of zooplankton species(100 species)was significantly higher than that of the other three months in June,and the number of pelagic species(44 species)was the least in December.From the perspective of different habitats,the number of species in the main lake area(98 species)was significantly higher than that of other waters,and the number of species in the Xihe River estuary(45 species)and the Fuhe estuary(42 species)was the least.The seasonal variation of the number of rotifer species was significant,and the number of species of cladocerans and copepods did not change much in different seasons.The main dominant species are: rotifers,snails,scorpions,long-nosed elephants,and nauplii.2.The spatial and temporal differences in zooplankton density and biomass are significant,and the time difference is more significant.The average density and biomass of zooplankton in the main lake area of Poyang Lake were 118.89 ± 29.94 ind./L and 1.04 ± 0.35 mg/L,respectively,which were generally higher than other areas.The density of zooplankton(8.19±4.06 ind./L)and biomass(0.13±0.06 mg/L)were lower than those of the other 3 months in December,and the zooplankton density(87.59±18.29 ind./L)was the highest in November.The zooplankton biomass(0.69±0.23 mg/L)was the highest in September.The results of NMDS analysis showed that there were significant time differences in zooplankton community characteristics in the eight waters,and the species composition and density time of zooplankton in the main lake of Poyang Lake was the most significant.4.Water turbidity,chlorophyll a content,dissolved oxygen,pH value and water temperature have significant effects on Poyang Lake and its connected waters and zooplankton community structure.Most dominant species(9 species with the highest dominance)were significantly positively correlated with turbidity,chlorophyll a content,dissolved oxygen,pH and water temperature,but the correlations between dominant species and different environmental factors were also different.The rotifers are more suitable for the habitats with high dissolved oxygen and high pH.The rotifers are more suitable for habitats with high water temperature and high concentration of chlorophyll a.5.The zooplankton community in Poyang Lake has changed significantly in the past three decades.The number of rotifer species increased,and the number of cladocerans increased first and then decreased significantly.The number of copepods did not change much,and the density and biomass of zooplankton increased first and then decreased.The connectivity of rivers and lakes remained The diversity of zooplankton is of great significance.On the one hand,it has a direct impact on the zooplankton community structure by promoting the exchange of zooplankton species between waters.On the other hand,the influence of rivers and lakes on the water environment indirectly affects the zooplankton community structure.