Study On The Community Structure Of Macrozoobenthos In Poyang Lake

In recent years, the common interference of artificial and natural factors has caused the reduction of water and the deterioration of water quality in Poyang Lake.Especially in 2011, Poyang Lake suffered the most serious drought in 60 years, which lasted from spring to summer and affected people's normal life and production in the basin, and Threatened exist of aquatic organisms(including macrobenthos) at the same time. Therefore, more and more people called for the establishment of Poyang Lake water conservancy project. Based on the one-year monitoring data on benthic animal of Poyang Lake, this essay analyzes the species composition, richness, density and biomass of zoobenthos in Poyang Lake. With the simultaneous determination of Poyang Lake's main physicochemical factors, it also analyzes the main environmental factors affecting the macrobenthos community structure in Poyang Lake. it will evaluate the water quality in Poyang Lake by using two kinds of diversity indices and five physicochemical factors, Respectively. At the same time by taking Junshan Lake as an example, the essay will study the influence of Lake barrier on benthic animal community structure, thus providing reference for biodiversity conservation in Poyang Lake. The results show that:1 This one-year monitoring has collected 41 types of benthic animal, including 2types of aquatic Oligochaeta, 14 types of aquatic insects, 19 types of mollusc(including 6 species of Gastropoda, 13 of Bivalvia) and 6 other species. According to the functional feeding groups, including collector-gathers 12, 7 species of predators, 6species of scrapers, collector-filterers 15, 1 species of shredders.2 The number of benthic animal species in Poyang Lake is not obvious in temporal distribution, seasonal species number between 21 and 24; the number of different species in each group is similar. In spatial distribution, the number of species 15# has the biggest to 17; the species 5#, 9#, 14#have the least number 6. Corbicula fluminea,limnoperna fortunei, gammaridae sp., nephtys oligobranchia and branchiura sowerbyi are the dominant species of zoobenthos in Poyang Lake, and each season the dominant species can change a lot.3 The annual average density and biomass of benthic animal in Poyang Lake is respectively 233.83 ind./m2 and 241.318 g/m2. In the distribution of time and space,the change of benthic animal's biomass is more obvious than density. In four seasons,autumn has the highest density and spring less, then summer, winter least; Changes of biomass in different seasons is winter has the most, autumn less and then spring,summer least. In each lake zone, the lake outlet has the maximum numbers of species and highest density, while the main lake has less numbers of species and lower density and estuary area has the least numbers and lowest density, which shows that drought forced benthic animal moved into deeper waters; and the change in the lake benthic animal is: the main Lake has the most, the lake outlet less and Estuary least.The lake benthic animal functional feeding groups were different.4 By using cluster analysis and non-metric multidimensional scaling analysis, we can divide the 15 monitoring points into four groups, finding that different groups have distinguished community structure and there are significant differences between the various feeding functional groups.5 The main environmental factors affecting the benthic animal community structure are nitrate, phosphate and total phosphorus. Calculation structure of 3 diversity index shows that the benthic animals have remarkable seasonality. When using the biological index to evaluate the water quality, we find that most of the points locate in the moderate pollution level; and the physicochemical index evaluation results also show that in the dry seasons the water is in eutrophication level, and in rich water period the water is in nutrition level.6 Junshan Lake is affected by the barrier and fishery, so the number of species of benthic animal is less to17, half of which are chironomus semireductus and Nephtys oligobranchia. And macrobenthos species mainly have stain resistance, low diversity.Therefore, the water conservancy will cause a certain impact on the community structure of zoobenthos.