The Characteristics of Protozoan Community Structure in the Urban Rivers of Shanghai in Winter

Community structure and biodiversity of protozoa in four restored urban rivers in Shanghai(Wuchaogang,Henggang,Chaoyang and Caoyanghuanbang River)were investigated from November 2007 to January 2008.88 different protozoa species were identified,including flagellates(31 species),sarcodinas(13 species),and ciliates(44 species).Results indicated that the rivers were mainly dominated by pollution-tolerant species,such as Bodo sp.,Monas sp.,and Cryptomonas sp.except for the Caoyanghuanbang River.In all four rivers,the species number of ciliates and flagellates were observed to be much higher than those of sarcodinas.The average diversity index of the protozoan community in the four rivers varied in the range of 1.14 to 2.87,and the density was 900.35～2837.89 ind/ml.Caoyanghuanbang River,which had been restored successfully before,had the characteristics of higher biodiversity,density and no dominant species,while in the three other rivers,the community structure was much simpler and the pollution-tolerant species were the dominant species.Overall,the results suggested the river environment could be improved effectively by reasonable human-induced restoration.Thus,evaluating the community structure of preliminarily restored river ecosystems,exploring effective strategies of restoration as well as making reasonable maintenance will be very important for these systems in their fragile and unstable states.