The Community Structure Of Main Groups Of Zooplankton And The Evaluation Of Water Quality In Taihu Lake Basin In Zhejiang Province

To investigate community structure of zooplankton and water quality in Taihu Lake basin of Northern Zhejiang, we collected and measured zooplankton and water samples in Jul 2013(summer), Oct 2013(autumn), Jan 2014(winter) and Apr 2014(spring), respectively. The results were as follows: First, water nitrogen and phosphorus content exceeded water quality standard seriously in most samples of Taihu Lake basin of Northern Zhejiang. Total nitrogen(TN) was 3.04mg/L, which was in excess of V Type of water quality standard. Total phosphorus(TP) index and chemical oxygen demand(COD) index were between type Ⅱ and Ⅳ. They were 0.15mg/L and 28.01mg/L respectively. Second, the change of average evaluation points of physical and chemical indexes was large in the Basin, which was 3.63~7.19, and it indicated that water quality was between type andⅢ Ⅴ. The average evaluation points of Beijing-Hangzhou Grand Canal in Zhejiang Province was significantly higher than the other three rivers, and the West Tiaoxi River was the lowest. The overall water quality of the Taihu Lake Basin of Northern Zhejiang was in a state of slight to middle eutrophication. Third, in Taihu Lake Basin of Northern Zhejiang, we have found 47 species of rotifers and 33 speices of planktonic crustaceans, the densities of which were 10287.27 ind./L and 323.55 ind./L, respectively. Rotifers, more dominant than crustaceans, contributed much more to the zooplankton community. Fourth, the Shannon-weaver index(H) of zooplankton was 0.10~3.35, which suggested that most samples were in mild or moderate pollution level.Fifth, the density of zooplankton was significantly correlatd with water temperature and conductivity, while the biodiversity of zooplankton was significantly related with water temperature, dissolved oxygen(DO), chlorophyll a(Chl-a) and TP.This study revealed that Taihu Lake basin was in a state of slight to middle eutrophication. Biodiversity index and physical and chemical indexes were utilized to reflect the long-term dynamic characteristics of the water quality of Taihu Lake basin of Northern Zhejiang. This research will help to trace the reason of pollution, and provide the theoretical basis for improving the quality of water and implementing protection.