Zooplankton Community Structure And Its Relation To Environmental Factors In Dianshan Lake

As the largest natural freshwater lake in Shanghai, Dianshan Lake is an important protected area of water source and ecological reserve in the upper reaches of the Huangpu River. It plays different roles in shipping, fishery, tourism, agricultural irrigation and drainage, flood storage and so on. Zooplankton is the basic link of the food chain and biological productivity of lake ecosystem, which plays an important role in the ecosystem of the lake and element cycle and controls the material circulation and energy flow of the whole ecological system.From January 2013 to December 2014, conducting qualitative and quantitative samples collected of zooplankton of the 12 sampling sites set in Dianshan Lake in the middle of each month, and studing the composition of zooplankton species, biomass, the dominant species etc. Zooplankton Community Structure and its relation to environmental Factors in Dianshan Lake and evaluate the water pollution and nutritional status by using diversity index, environmental factors and so on. The main results are as follows:1. There are 76 species of zooplankton in Dianshan Lake, including 60 species of rotifers, which is the largest number of species, Rotifers are belonging to 2 classes, 3 orders, 13 families, 20 genera, and the species numbers of Trichocerca are 14, it is more abundant. There are 8 species of copepods and cladoceras, copepods are belonging to 2 classes, 2 orders, and cladoceras are belonging to 3 classes, 3 orders.2. The dominant species in Dianshan Lake are Polyarthra sp, Synchaeta sp, Keratella cochlearis, Brachionus angularis, Filinia longiseta, Nauplii.There is a significant phenomenon that the dominant species have seasonal, Polyarthra sp is the first dominant species, which advantage of the four seasons. Synchaeta sp is the dominant species in spring,autumn and winter, which are advantage at low temperature. Anuraeopsis fissa is dominant species in spring, Hexarthra intermedia is dominant species in summer.3. The monthly variation range in quantity of zooplankton in Dianshan Lake is 465-8556 ind./L, while the monthly variation range in quantity of rotifera, copepods and cladocerans are 83-8264 ind./L, 2-450 ind./L and 0-146 ind./L respectively, and rotifers make the largest contribution to the quantity. The annual average variation range in quantity of zooplankton of every sampling site in Dianshan Lake is 1133-3506 ind./L, while the annual average variation range in quantity of rotifera, copepods and cladocerans are 1014-3365 ind./L, 62-177 ind./L and 20-69 ind./L respectively. The annual average of zooplankton in quantity decreases from northeast to southwest in space, which has obvious seasonal variation, it is high in the spring and summer and low in the autumn and winter.4. The monthly variation range in biomass of zooplankton in Dianshan Lake is 0.63-6.76 mg/L; while the monthly variation range in biomass of rotifera, copepods and cladocerans are 0.03-4.19 mg/L, 0.01-2.55 mg/L and 0-1.24 mg/L respectively. The annual average variation range in biomass of zooplankton in Dianshan Lake is 1.61-3.63 mg/L, while the annual average variation range in quantity of rotifera, copepods and cladocerans are 0.68-2.23 mg/L, 0.52-1.62 mg/L and 0.08-0.32 mg/L respectively. The annual average of zooplankton in biomass decreases from northeast to southwest in space, which has obvious seasonal variation, it is high in the summer and low in the winter.5. According to SPSS correlation analysis, getting that Water Temperature(WT) has the greatest influence on zooplanktons, followed by the Total Dissolved Solids(TDS), Total Suspended Solids(TSS), Transparency Degree(SD). The species and biomass of zooplankton, the diversity index and evenness index, which have significantly positive correlation with water temperature and significantly negative correlation with SD index. And there is a positive correlation relationship between the quantity of dominant species and the chlorophyll a.6. The water quality and the pollution status of Dianshan Lake are evaluated by using biological diversity index, the physicochemical factors and dominant species. The physicochemical factors and Carlson trophic state index of Dianshan Lake point out that the water is heavy eutrophic; the dominant species indicate that the eutrophy of water is between middle-heavy. So it is easy to conclude that the eutrophy of water in Dianshan Lake is between middle-heavy. The dominant species in Dianshan Lake indicate that the water pollution has reached β-middle. Shannon-Winier biodiversity index indicates that the water is heavy polluted. In summary, the water pollution in Dianshan Lake is generally between middle-heavy.