Community Structure of Rotifera and Ecological Assessment of Water Quality in Qiandao Lake

Abstract

The community structure of Rotifera and ecological assessment of water quality, including species composition, population dynamics, standing crops and indicator organisms, E/O and Q-B/T index, was studied in a large, deep lake, Qianda Lake, Zhejiang Province. After one-year monitoring in situ, 70 species of Rotifera were found, 41 species were pollution indicator species, of which oligo- βmesosaprobic, βmesosaprobic andβ-αmesosaprobic species accounted for 41. 5%, 36. 5% and 22. 0% of the total indicator species, separately. In terms of annual average density, the dominant species were Keratella cochlearis, Trichocerca similis and Polyarthra trigla, which accounted for 59.2% total density. Asplanchna spp. accounted for 56.5% of total biomass. The annual average density of Rotifera was 103 ind. /L, and biomass was 0.069mg/L. Except for Keratella cochlearis, which form stable population, the density distribution of other dominant species were varied temporarily from station to station, such as Schizocerca diversicornis density reached SOOind. /L at station II in May, Trichocerca similis density reached lOOOind. /L at station III in July, and Keratella cochlearis density reached 560ind. /L at station VI in September. Biomass changes in space and times were determined by Asplanchna spp, the higher biomass at station I and II in May, reached 0.169 mg/L and 0.275 mg/L, separately. The ranges ofE/O values in Qiandao Lake were 0.29-0. 62(0.46 on average), and the ranges of Q-B/T values were 0.17-1.50(0.68 on average). The regression analysis showed that the transparency of lake water had negative linear relationships with E/O value (r~2= 0.7182) and QB/T value(r~2= 0.7747). The characteristics of Rotifera community in Qiandao Lake showed the rich species number and low density, biomass and QB/T value compared with other large shallow lakes in China. Furthermore, biological assessment of water pollution and trophic condition were evaluated by species indicators, biotic index of E/O and Q-B/T. The trophic type of Qiandao Lake could be regarded as oligo-βmesosaprobic, of which station I , II and V were considered as P mesosaprobic, while others were considered as oligo-βmesosaprobic.