Dynamics of Species Composition,Biomass and Diversity of Rotifer in Shahu Lake

The dynamic of rotifer composition,biomass and diversity in Shahu Lake,Ningxia,was studied from April of 2008 to Month of 2009.A total of 14 categories 23 species were identified,among which Brachionus angularis,Keratella vaigavalga,Filinia longiseta,Polyarthra trigla,B.calyciflorus and Rhinoglena frontalis were dominant species.Seasonal distribution trend of rotifer species was spring(19)summer(14)autumn(10) and winter(10).The average annual rotifer density and biomass was 347 ind./L and 0.290mg/L,respectively.Seasonal distribution of rotifer density and biomass tendency was autumn(547ind./L and 0.447 mg/L)summer(345ind./L and 0.428mg/L),spring(323ind./L and 0.186mg/L)winter(175ind./L and 0.099mg/L).Spatial distribution of the rotifer density and biomass was Bird Island eleventh team old fisheries the middle of a lake intake portion.The average annual Shannon-Wiener diversity index among all sampling sites(H′) was 2.018(ranged from 1.519 to 2.720);mean Margalef diversity index(D)was 1.441(ranged from 1.096 to 2.523);while mean Pielou diversity index(J) was 0.636(ranged from 0.456 to 0.857).The characteric of rotifer species composition and the relationship between environment factors and rotifer density was analyzed.Moreover,water pollution and trophic condition in Shahu Lake were evaluated by species biodiversity index.