Rotifer species are cosmopolitan and the endemism is very low. They are highly susceptible to physical and chemical changes in their environment due to their small size and permeable integument, and they are known to be an important link between the microbial loop and higher trophic levels, so rotifer is an excellent indicator of the water status of a lake. Yangcheng Lake is one of the most important freshwater lakes in China. The total area of the lake is 119.04 km2,aquatic plants are dense providing a food source for crabs and the lake yields high numbers of the Chinese mitten crab(Eriocheir sinensis). Currently, although the ecological effects of the pen culture on the environment have received extensive attention,expert mainly focus on aquatic plants, physical and chemical factors, environmental effects and benthic animals, but rarely reported on the rotifer community structures. To date, no studies have been done on rotifers in Yangcheng Lake in detail. Thus, the aim of this study was to analyze the spatial and temporal variation of rotifer community structure and species diversity in net-pen closing and lake areas, in order to provide the data and theoretical basis for aquatic ecosystem of Yangcheng Lake, biodiversity conservation and sustainable development of ecological-pen-culture. Rotifer community structure and several feature parameters of water quality were investigated in 3 controlled sites in net-pen closing and lake areas of Yangcheng Lake, during June 2008 to May 2009. The relationship of rotifer community structure and environmental parameters was analyzed, various parameters were used to assess the water quality. The totals of 83 rotifer species were collected, belonging to 30 genera and 12 families. The study showed that the annual average density and biomass of 3 sites in net-pen closing were lower than those in lake areas, density exhibited significant positive correlations with temperature. The CCA biplot of samples and environmental variables showed that rotifer assemblages followed a water temperature gradient,suggesting that water temperature was the most important factor in determining seasonality, but the Ph was the lowest. Different months were affected by different environmental parameters, there was no differentia in sites except April. The CCA biplot of species and environmental variables shows that the warm-stenotherm species like Trichocerca sp. , Anuraeopsis fissa, Hexarthra mira in the down-left quadrant have strong positive correlations; the cold-stenotherm species like Keratella quadrata, Synchaeta sp. In the top-right have strong negative correlations; the eurytherm species like Polyarthra trigla and Keratella cochlearis are in the middle of the biplot, which support these two species are dominant ones in a year. According to the Jaccard similarity index (Sj), the high similarity in dominant species occurred between net-pen closing and adjacent lake areas. Water quality showed that 6 sites were all eutrophication and β-α mesosaprobic, although there was a slight degree in sites C1 and A1, no significant differences in 6 sites, which was similar to the results by TSI.%2008年6月至2009年5月对阳澄湖养蟹网围及湖区3组对照点中轮虫群落结构及部分水质特征参数进行调查,分析了轮虫群落结构与环境变量的关系,利用多种参数对其水质进行评价.经鉴定,共采集到轮虫83种,隶属于12科30属.研究表明,网围内3个采样点的年平均生物密度及生物量低于湖区3个采样点,生物密度与水温呈极显著正相关(P＜0.01).不同月份受不同环境变量的影响,除4月份外,环境变量对生物密度的影响在采样点之间无差异.相似度分析表明,网围内及相邻湖区的轮虫优势种相似性高.水质分析表明,6个采样点均为富营养化、β-α中污染水体,东湖网围C1和中湖网围A12采样点程度稍轻,但6个采样点之间无显著性差异,这与用卡尔森营养状态指数得出的结果相似.
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