Zoobenthos Community Structure And Evaluational Research Of Water Quality In The Downstream Of Nenjiang River

The ecological study of zoobenthos was conducted on ten typical sampling sections selected in the downsteam of Nenjiang River, in spring, summer, and autumn in2011. Zoobenthos communities and biodiversity were examined with multivariate statistic analysis. The gray association analysis was used to detect the correlation between zoobenthos and environmental factors. The purpose of this paper was to provide a guideline of management and a foundation for the future study in the downsteam of Nenjiang River.Total of98species were identified, among which, the majority are aquatic insects (69), accounting for70percent; followed by molluscs,16species, accounting for16%; eight kinds of annelid, accounting for8%; four crustacean species, accounting for4%; one platyhel-minthes species, accounting for1%.The total mean abundance and biomass were35.45ind./m2and3.15g./m2. The temporal and spatial distribution of abundance and biomass were spring> summer> autumn, the spatial variation for the upstream and middle reaches is higher than the downstream, such differences associated with environmental factors in the distribution.There were different ranges in different diversity index, Shannon-Wiener index throughout the year between1.36-2.75, the highest in spring, to2.75, the lowest in autumn, to1.36; Pielou index throughout the year between0.58-0.86, the maximum value appears in the spring, to0.86, the minimum value appears in the autumn, to0.58; Simpson Biology index throughout the year between2.57～6.06, the maximum value appears in the spring, to6.06, the lowest in the fall, to2.57.The trend of Shannon-Wiener index、Pielou index and Simpson Biology index are spring> summer> autumn.The hierarchical cluster analysis revealed that the zoobenthos community structure in downsteam of Nenjiang River was classed four groups, the comparability is high within groups and the great change between groups. The results of nor-matric multi-dimentional scaling (MDS) was basically the same of the hierarchical cluster analysis, was classed four groups, and showed the change was for the change of hydrographic factor and vegetation.The correlation between density and biomass in spring, summer and autumn with various environmental factors is different, the results showing the impact of the various environmental factors on zoobenthos communities.The result of grey relational analysis suggested that the greater impact on the density for the conductivity, pH and chlorophyll a. This will be the main factors which influence the large benthic animal species composition and distribution of the downstream of Nenjiang River.