Community structure of rotifers and ecological assessment of water quality in the tidal Guangzhou segment of the Pearl River

Community structure of rotifers was investigated at two different sites in the tidal Guangzhou segment of the Pearl River with monthly sampling from April 2008 to March 2010.Transparency,Chlorophyll a(Chl a),Total Nitrogen(TN),Total Phosphorus(TP) and other physicochemical parameters were also measured simultaneously.Trophic state of waters was evaluated through non-biologic environmental factors.Ecological assessment of water quality was also carried out through the analysis of species composition of rotifers and E/O index.During the survey period,66 species of rotifer were recorded and 46 species belong to pollution indicator.Lififerotrocha subtilis,Anuraeopsis fissa,Filinia novaezealandiae and Brachionus angularis were the dominant species.The abundance of rotifers ranged from 69 to 5 200 ind./L with the highest value at Zhongda pier site,The peak value of abundance was observed in the dry season.There was significantly positive correlations between pH,nitrogen-phosphorus ratios and rotifers abundance(P0.05).A significantly negative correlation was detected between temperature and rotifers abundance(P0.05).According to the ecological assessment of water quality,Guangzhou river segment had reached the level of hypereutrophication,in accordance with the comprehensive evaluation of trophic state of non-biologic environmental factors.