Comparative Study On Community Structures Of Zooplankton In Dishui Lake And Its Surrounding Waters

Dishui Lake is located in Lingang New city, China, which is the largest man-make lake in China, and is the center of Lingang water system. Dishui Lake plays an important role in shaping the urban landscape ecology, and the microclimate. It is directly connected to the future development and tourism of the new city. Furthermore, it can reflect the water quality status of Shanghai. Water in Dishui Lake comes from the surrounding waters. Therefore, the quality of the surrounding waters can influence the water in Dishui Lake. Zooplankton in Dishui Lake had been sampled from 2008 to 2009. Zooplankton in the surrounding waters had been sampled since March, 2009. The community structures of zooplankton in the lake and the surrounding waters were compared, in order to know the succession of the zooplankton community structure and its specificity. Furthermore, predict the pollution status of the waters. It provides the biology basis for the water protection and the future tourism development. The main results are listed as follows: 1. There are 49 species of zooplankton in Dishui Lake, which belong to 23 genera of 17 families. There are 38 species of Rotifera, belong to 15 genera of 9 families.There are 8 species of Copepoda, belong to 5 genera of 5 families, 3 species of Cladocerca, belong to 3 genera of 3 families.The average abundance of zooplankton in Dishui Lake was 2448 ind/L, in which the average abundance of rotifer accounted for 99%, the copepod accounted for 1%. The cladocerca were very few which could be ignored. The average biomass of zooplankton was 2.15mg/L, in which the average biomass of rotifera accounted for 97%. The average biomass of copepod accounted for 3%.There are eight dominant species of rotifers in Dishui Lake: Synchaeta sp., Trichocerca pusilla, Anuraeopsis fissa, Encentrum sp., Polyarthra vulgaris, Keratella eichwaldi, Flinia brachiata, Brachionus angularis. The dominant species of copepod is larva. The cladocerca are not dominant in Dishui Lake.The community structure of zooplankton in Dishui Lake is well-distributed. There are little differences among the sites.2. There are 112 species of zooplankton was identified in the surrounding waters from March to December in 2009. There are 83 species of rotifera, which belong to 26 genera of 10 families. There are 9 species of copeod, which belong to 7 genera of 5 families. There are 20 species of cladocerca, which belong to 12 genera of 5 families. The abundance of zooplankton is between 1183 and 9730 ind/L, and the biomass is between 0.97 and 8.06mg/L.There are 12 dominant species of rotifera in the surrounding waters: Polyarthra vulgaris, Synchaeta sp., Trichocerca pusilla, Encentrum sp., Anuraeopsis fissa, Keratella tropica, Keratella eichwaldi, Keratella cochlearis, Brachionus valiabilis, Brachionus plicatilis, Asplanchna sieboldi. The dominant species of copepod is the lavel. There are no dominant species in cladocerca. The dominant species in different site are different, but Polyarthra vulgaris, Synchaeta sp. are the same dominant species among the eight sites in the lake.3. Comparing with the surrounding waters during the same time, the species of the zooplankton in Dishui Lake were poor, which only accounted for 1/3 in the surrounding waters. The species in the surrounding waters were rich, which had great difference among the different waters.Among the surrounding waters, the abundance of the zooplankton in Dazhi River (W1) and Center of the farm river (W2) were less than Dishui Lake. However, the abundance of the zooplankton between the tape grass district (W9) and the sea gate district (W13) were similar to the lake (2320ind/L and 2893ind/L). The abundance of zooplankton in the other sites was between 3290 and 9730 ind/L.The main dominant species in Dishui Lake was Trichocerca pusilla, whose relative abundance was 0.25. The main dominant species in the surrounding waters is Polyarthra vulgaris. Its relative abundance was between 0.25 and 0.51. The variation of the dominant species changes with the seasons distinctly.However, Polyarthra vulgaris was the dominant species in most time of the year, which had little change. The community structures of the zooplankton in the surrounding sites were simple.According to the ecological evaluation criterions, the results showed that the water quality of Dishui Lake was at semi-eutrophic level. The water quality of the surrounding waters was at middle-eutrophic level.