Community Characteristics Of Rotifers In Guangzhou Segment Of The Pearl River And Modaomen Estuary

Physicochemical parameters and rotifer communities were investigated in Guangzhou segment of the Pearl River from April 2007 to April 2010, and in Modaomen waters from July 2009 to January 2010. The main results are as follows:1. Seventy-six species of rotifers, in which fifty-one species were pollution indicator rotifers, were recorded at two sites in Guangzhou segment of the Pearl River. The dominant species were Lififerotrocha subtilis, Anuraeopsis fissa, Filinia novaezealandiae and Brachionus angularis. The abundance of rotifers ranged from 69 to 6038 ind. L-1 with the highest point appeared at Zhongda pier and the average abundance 1891±1282 ind.L-1. The rotifer abundance peak at the two sites appeared in the dry season. Significantly negative correlations were found between runoff and rotifer abundance which had obviously positive correlations with the pH value and nitrogen-phosphorus ratios. The analysis results of RDA showed that chlorophyll a (Ch1 a), transparency and nitrogen-phosphorus ratios were the most important factors that influenced the spatial and temporal distributions of community structure of rotifers.2. Sixty-nine species of rotifers, in which fifty-one species were pollution indicator rotifers, were recorded at three sites in Modaomen waters of the Pearl River estuary. The dominant species were Polyarthra vulgaris, Keratella cochlearis, Keratella tropica and Trichocerca pusilla. The abundance of rotifers ranged from 0 to 199 ind. L-with the highest point recorded in the sampling site of the stagnant district and the average abundance being 31±54 ind. L-1. The rotifer abundance peak at the three sites was recorded in the wet season. Significantly negative correlations were found between salinity and rotifer abundance which had obviously positive correlations with water temperature, Total Nitrogen (TN) and Chlorophyll a (Ch1 a). The violent changes of physicochemical factors in Modaomen estuary and the large fluctuations of diversity index of rotifers indicated that the community structure of rotifers was unstable. The analysis results of RDA showed that water temperature, salinity and Chlorophyll a (Ch1 a) were the most important factors that influenced seasonal variations of community structure of rotifers. 3. According to the ecological assessment indicators of water quality, waters in Guangzhou segment of the Pearl River (E/O= 2.83, QB/T= 1.75) had reached the level of hypereutrophication, and waters in Modaomen estuary (E/O= 1.62, QB/T= 1.38) the level of mild eutrophication, which coincided with the results of the comprehensive evaluation of trophic state of non-biologic environmental factors.