PRIMARY STUDIES ON PLANKTON ROTIFERS AND WATER QUALITY ASSESSMENT IN XIANGXI BAY OF THE THREE GORGES RESERVOIR

Xiangxi River was the biggest tributary of the Three Gorges Reservoir in Hubei Province,which had a length of 94km,a catchment area of 3, 099km2 and a natural fall of 1540m. Since June 1st, 2003 the segment of Xiangxi River from the rivermouth to Xiakou had been formed the backwater region. In this region the spatial and temporal distribution of plankton rotiferswere investigated at monthly intervals from July, 2003 to June, 2004. Among the 80 rotifer species identified, 13 species werepredominant,which were Synchaeta sp.,Keratella cochlearis, Polyarthra trigla, Conochilus unicorni, Trichocerca lophoessa, Trichocercagracilis, Brachionus angularis, Keratella valga, Tichocerca similes, Brachionus forf icula, Brachionus Calycif lorus, Trichocercaporcellus and Pompholyx sulcata. A maximum density of 2459.23 ind./L was observed in September and the minimum ofrotifer density was found in December(85.00 ind./L). ANOVA was used in the variance analysis of rotifer density in differentmonths, the result was found that rotifer density,Margalef and Shannon-Wiener diversity index significantly different(n= 12, P0101), so the temporal dynamic of rotifer density in Xiangxi Bay was obvious.At the same time, the spatial distribution of rotifersin this region was discussed. The highest density of rotifer was found in Site, the least density was found in Site . Rotiferdensity decreased along the water flow. And all the sites could be divided into 4 groups by the cluster analysis, the first groupwas from Site to |the second group was Site |the third group was Site and⑾, and the fourth group was Site?Rotiferdensity was evidently positive correlation with temperature, but negative correlation with water depth. The main factors regulatingrotifer population were water temperature and food resource.Also in this article the relat ionship between rotifer and waterquality was discussed.