Analysis on biological composition and food-chain structure in the urban rivers of Shanghai

The community structure,biodiversity and dominant species of the four urban rivers in Shanghai(Caoyanghuanbang River,Henggang River,Wuchaogang River and Chaoyang River) were investigated during the period of Nov.2007 to Oct.2008.Totally,268 species of phytoplankton, 157 species of zooplankton,21 speices of macrobenthos,10 speices of higher plants and 13 speices of fish were identified.In phytoplankton,Chlorophyta,Euglenophyta,Bacillariophyta, Cyanophyta had the highest richness.There were 94 species of protozoan,44 species of rotiferan,13 species of cladoceran and 6 species of copepodan in the zooplankton group;the macrobenthos included 14 mollusks,3 annelidans,2 crustaceans and 2 insect larvaes;fishes belonged to 7 families in which Cyprinidae was the most abundant species(53.8%).Higher plants included 4 species of submerged plants,4 species of emerged plants and 2 species of floating plants.The biodiversity of phytoplankton,zooplankton,macrobenthos,fish and higher plants were much higher in Caoyanghuanbang River than the other three,and there was no dominant species for each group,and vegetation was of high density and mainly was emerged-plants. While,in Henggang River,the biodiversity of phytoplankton was the lowest and mosquito-eating fish was the only vertebrate species,the most abundant plant was the submerged species.The biomass in Wuchaogang River and Chaoyang River was the lowest among the four rivers in which the dominant species of phytoplankton were Cyanophyta and Chlorophyta.The four rivers were all identified as having simplified food webs based on the analysis of the community composition and distribution of the dominant species.Further suggestions were made that the process of ecological restoration should be different due to the different biotic-component-types of rivers with the aim of enhancing the community structure and the food-chain construction.