Studies On Community Structure Of Rotifers In The Guangzhou Segment Of The River Pearl And The City Lakes

The spatial and temporal distribution of planktonic rotifers in the Guangzhousegment of the River Pearl and lakes, was studied at one-month intervals from December2005 to November 2006. Total 77 species of rotifer belonging to 21 genera and 13families were identified during the survey period. The dominant species in the riversegment are found were Liliferotrocha subtilis,Anuraeopsis fissa,Trichocercapusilla,Brachionus angularis and Brachionus caudatus; and Trichocerca pusilla,Liliferotrocha subtilis,Anuraeopsis fissa and Brachionus forficula in the lakes,respectively. The higher densities of rotifers were recorded in the February to Marchand August, 2006. The lower densities were in the rainy season (flood period). Thehighest density was 5494 ind./L (Zhongda, Dec, 2005), the lowest was 117 ind./L(Zhongda, July, 2006). Among the 4 sample sites, the highest annual average densitywas recorded at Tianhe (1260 ind./L), followed by Zhongda (1123 ind./L) andHuangpu (737 ind./L), the lowest at Liuhua (781 ind./L). The higher frequency ofsmall-sized animals was found in the 4 sampling sites, and the higher frequency of thelarge-sized animals at Huangpu and Zhongda. River discharge and salinity haveimportant effect on the density fluctuation and species composition of rotifers. Theimportance of temperature in determining rotifer community structure and seasonalsuccession are analyzed. Results indicate that rotifers play important role in the riverand lake ecosystems.