AbstractThe annual dynamics of community structure and species diversity of rotifers in the Wuhu section of the 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 of 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 the 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). 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 the community (n=12,r₁=0.600,P<0.05; n=12,r₂=0.955,P<0.001), but negatively associated with dominance (n=12,r=-0.942,P<0.001).