Research On The Macrozoobenthos Community Structure And Water Quality Evaluation In Shahu Lake, Ningxia

In order to study the community characteristics of macrozoobenthos in Shahu Lake, seasonal surveys on macrozoobenthos were conducted in 8 sampling sites of Shahu Lake in spring, summer and autumn of 2013, respectively and assess the water quality. The results indicated that 17 macrozoobenthos species were identified in the survey, which can be classified into 6 families, mainly including of Insecta, Mollusca and Annelida, and varied significantly in different seasons and different sites. Dominant macrozoobenthos community in Shahu Lake was aquatic insect larvae.Annual average density and biomass of macrozoobenthos in Shahu Lake were 2379ind./m~2 and 177.86 g/m~2, respectively. Variance analysis indicated that species, density and biomass of macrozoobenthos in Shahu Lake were varied significantly between different seasons and different sampling sites (p<0.01). Statistic analysis revealed that the maximum density and biomass was in summer(15species), next in spring(6species), the lowest in autumn(4species); the maximum density was 9616ind./m~2in summer, next in spring (226.9 g/m~2), minimum in fall (152.97g/m~2). The difference between the number of species in the cross section was that the number was high (15 species), the lowest number was Donghu Lake(5species). The maximum density was 227.18g/m~2 in Canal entrance (227.18g/m~2), (16.72 g/m~2), The spatial and temporal distribution of species, density and biomass were variance due to the water environmental factors. Macrozoobenthos biological indices were generally low in the survey. Shannon-Wiener index and Margalef index were 0.91 and 0.51, respectively. The number of Macrozoobenthos species was low in Shahu, and the biological index was low. According to the biological index and water environment data of Shahu, the water quality of Shahu was evaluated. The results showed that the water quality of Shahu Lake was mostly in the third-fourth parts. Water quality in Shahu Lake as a whole was a serious pollution, and the most serious pollution in summer, slightly better than that of in spring.Applying Canonical Correspondence Analysis (CCA) and Redundancy Analysis (RDA) to analyze the behavior of macrozoobenthos in Shahu Lake, the results have shown that the level of nitrate nitrogen, pH and chloride were the main restricted factors of the activities of macrozoobenthos in Shahu Lake; besides, water temperature and dissolved oxygen saturation also have certain level of influence to the species. Environmental factors that effects the activities of macrozoobenthos in Shahu Lake were also different in seasons, which implied their influence to the distribution of macrozoobenthos community. The activity of macrozoobenthos in spring was strongly correlated to the BOD5, which in summer was mainly effected by the turbidity, while in autumn was ammonia.According to the indice and the distribution of macrozoobenthos, the water quality in Shahu Lake was severe pollution, and pollution was the worst in summer, and in autumn was slightly better than that in spring. RDA analysis showed that the number of macrozoobenthos in summer in Shahu Lake was mainly affected by turbidity. Change of the main limiting factor that summer and autumn lake due to anthropogenic influences, external nutrient resulted in an increase in the lake water environment changes, also that the water quality in Shahu Lake were polluted seriously in summer and autumn, and the result was identical to that one of the water quality of Lake with the phy-chemical evaluation results.