Studies On Community Structure Of Rotifers In Wuhu Section Of Qingyi River And Lake Jinghu

The annual dynamics of community structure of rotifers in Wuhu section of Qingyi River and Lake Jinghu were studied in the year 2003, and the relationships between the rotifer density and some relevant ecological factors were also analyzed; Meanwhile, the water quality of Lake Jinghu was assessed. In addition, the density dynamics of common Brachionus species in Lake Jinghu and the seasonal variation of their body and egg volumes were studied. The main results were presented as following: 1. The annual dynamics of community structure and species diversity of rotifers in Wuhu section of Qingyi River was studied in the year 2003, and the relationships between rotifer density and ecological factors including water temperature, Chl-a concentration and river discharge were analyzed for further understanding on China rotifer fauna and the pattern of seasonal variation of rotifer density in rivers.One hundred and four rotifer species were identified, of which Cephalodella forceps, C. macrodactyla, C. mucronata, C. evabroedi, Lecane hornemanni, L. elsa, L. lunaris acus and Filinia camasecla were confirmed as new records in subtropical region of China. The dominant species were Keratella cochlearis, Polyarthra vulgaris and Ascomorpha ecaudis. The total density of rotifers was positively related to water temperature and Chl-a concentration (r=0.533, P<0.05; r=0.548, P<0.05) during January-April (before flood season), but it was positively correlated with river discharge (r=0.580, P<0.01) during May-September (during flood season), and with water temperature, Chl-a concentration and river discharge (multiple-linear regression, R²=0.680, P<0.05) during October-December (after flood season), respectively. River discharge had the greatest effect on the total density of rotifers during October-December (Standardized partial regression coefficient:β₁=0.312,β₂=0.120,β₃=0.593). Across the year, species diversity index was positively associated with number of species and species evenness of community (n=12, r₁=0.600, P<0.05; n=12, r₂=0.955, P<0.001), but negatively associated with the dominance (n=12, r=-0.942, P<0.001). 2. The annual dynamics of rotifer community structure in Lake Jinghu in Wuhu city in the year 2003 was studied, the water quality was ecologically assessed, and the relationships between the rotifer density and the main ecological factors including water temperature, pH, and the densities of small Ciliates, Cladocera and Copepoda were also regressively analyzed. Fifty-five species of rotifers were identified, which belong to 15 families and 21 genera. The dominant species determined according to annual average denstity and biomass included Anuraeopsis fissa, Trichocerca pusilla, Rhinoglena frontalis, P. remata, F. longiseta, P. vulgaris, Proalides tentaculates, and Asplanchna priodonta, P. tentaculates, T. pusilla, respectively. During the year, the total density of rotifer was positively correlated with water temperature (w), Chl-a concentration (c) and small Ciliates density (x) (multiple-linear regression, R₂=0.38, P<0.05), and water temperature had the greatest effect on the total density of rotifers (Standard partial regression index, β_w=0.684, β_c=-0.246, β_x=0.422). In spring and autumn, water temperature had the greatest effect on the total density of rotifers, respectively (β_w1=0.983,β_c1= -0.683;β_w2=0.642,β_c2=0.423,β_x2= -0.583), while in winter and summer, Chl-a concentration and the density of Ciliates had the greatest effect on the total density of rotifers, respectively (β_c1= -0.631,β_x1=0.566; β_w2= -0.225,β_c2= -0.154,β_x2=0.871). By means of three biological standards (QB/T, Shannon-weiner diversity index and Willams index, indicator organisms of rotifer species) combined with Physico-chemical quality of water, the small region of Lake Jinghu (stationâ… ) could be regarded as transition stage from oligo-βmesosaprobity to βmesosaprobity, while the big region (stationâ…¡) could be considered as βmesosaprobity. The lake might be a meso-eutrophic lake. Altho...