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

Dishui Lake is located in Pudong Qu Lingang New city, Shanghai, which is the largest man-made 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. Phytoplankton in Dishui Lake had been sampled from 2009 to 2010. Phytoplankton in the surrounding waters had been sampled since March 2009. The community structures of phytoplankton in the lake and the surrounding waters were compared, in order to know the succession of the phytoplankton community structure and its sp.ecificity. 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 are146 species of phytoplankton in Dishui Lake, which belong to 64 genera of 8 phyla. The abundance of phytoplankton is 1698×104ind/L; Chlorophyta is the main phytoplankton, following is Bacillariophyta and Cryptophyta. Phytoplankton biomass has obvious change with seasons, more in summer, less in winter. There are 8 dominant species in Dishui Lake: Merismopedia minima G.Beck, Chroococcus minutus (Kütz.)Nag., Chlamydomonas globosa Snow, Cocconeis placentula Ehr., Gymnodinium sp., Cryptomonas erosa Ehr., Chroomonas acuta Uterm and Chromulina pygmaea Nygaard.The community structure of phytoplankton in Dishui Lake is well-distributed.2. There are 223 species of phytoplankton was identified in the surrounding waters from March 2009 to December 2010, which belong to 86 genera of 8 phyla. The abundance of phytoplankton is between 425 and 1711×104ind/L, and the average biomass is between 2.60 and 9.79 mg/L.There are 11 dominant species in the surrounding waters: Cateria sp., Chlamydomonas globosa Snow, Scenedesmus bicaudatus (Hansgirg) Chodat, Scenedesmus quadricauda (Turp.)Brébisson, Cocconeis placentula Ehr., Melosira varians Agardh., Cyclotella meneghiniana Kützing, Nitzschia sp., Gymnodinium sp., Cryptomonas erosa Ehr. and Chroomonas acuta Uterm.The dominant species in different site are different, but Cateria sp.,Cryptomonas erosa Ehr. and Chroomonas acuta Uterm are the same dominant species in every sampling site.3.Cluster by spss software, Dishui Lake and the surrounding waters is divided into 6 habitat., which had great difference among phytoplankton. Among the surrounding waters, the abundance of the phytoplankton in Dazhi River (W1) , Center of the farm river(W2) and eelgrass growing aera(W9)were less than Dishui Lake. However, the abundance of the phytoplankton in base for algae-water and grass-water is closed to the Dishui Lake.The variation of the dominant species changes with the seasons is obvious in Dishui Lake, the surrounding waters is not obvious.According to the ecological evaluation criterions, the results showed that the water quality of Dishui Lake was at middle-eutrophic eutrophic level. The water quality of the surrounding waters was at eutrophic level.