太湖西岸湖滨带水生生物分布特征及水质营养状况

The characteristics of the Hydrobios' distribution and the analysis of water quality along the West Shore of Taihu Lake

对太湖西岸湖滨带入湖河口区浮游生物和底栖动物的种类、单位体积数量以及物种多样性调查的基础上，分析了该区域水生生物分布特征。研究表明，在调查到的5个浮游植物门类中，蓝藻和绿藻门种类占到46．81％和36．17％。单位水体中的物种数量分别占到总藻类的60．97％和34．49％，而硅藻门仅占到总藻类数量的3．07％。Shannon-Wiener物种多样性及均匀度指数基本在1．3—1．6和0．14—0．22之间波动。在调查到的71种浮游动物中，耐污染的桡足类和枝角类占36．62％。单位水体中的物种数量分别达到7．07×10^4个／L和7．76×10^4个／L；底栖动物群落结构趋于单一化，敏感种大量减少或消失，物种多样性指数值低下，日’及其均匀度值J仅分别为1．59和0．581左右。同时，部分耐污染和广布种大量繁殖，其单位水体中的物种数量平均占到底栖动物总量的84．76％。对入湖河口区24个点位的水质监测结果也表明，水体中的TN、TP浓度分别为3．50mg／L和0．28mg／L，分别高于国家湖泊水环境质量V类水质（TN≤2．0mg／L，TP≤0．2mg／L）标准。结合优势种和多样性指数水质分析方法，太湖西岸湖滨带水体水质已近严重富营养化程度。

Based on the survey of the species abundance, biomass per plankton and benthos along the west shore of Taihu Lake, we analyzed unit water volume and species diversity indices of the characteristics of the Hydrobios＇ distribution in this area. Five phytoplankton families were found in the survey, and the species of Cyanophyta and Chlorophyta accounted for 46.81% and 36.17% of total species abundance, the biomasses of these species were 60.97% and 34.49% of total algae biomass, respectively. In contrast, the biomass of species of Bocillariophyta accounted only for 3.07% of total algae biomass. The Shannon-Wiener diversity index and Even index generally fluctuated from 1.3 to 1.6 and from 0.14 to 0.22, respectively. Of the 71 species of zooplankton found in current survey, pollution-tolerant copepodas and cladocerans accounted for 36.62% of total species, and their biomass per unit water volume could reach 7.07× 10^4ind/L and 7.76× 10^4ind/L, respectively. The zoobenthos along the shore showed a simplified community structure, the abundance of environment-sensitive species decreased greatly and some species became extinct. Species diversity index of zoobenthos community along the shore was very low, with diversity index and even index only about 1.59 and 0. 581, respectively. Meanwhile, some pollution-tolerant and cosmopolitic species propagated rapidly, and their biomass per unit water volume accounted for 84.76% of total biomass of zoobenthos. Through a evaluation based on a combined method （ dominant-species assessment and diversity index assessment）, we concluded that the water quality along the west shore of Taihu lake showed a sign of severe eutrophication. This conclusion could also be confirmed by the results of monitoring of water quality at 24 sites of the estuary, which showed that the concentration of Total Nitrogen （TN） and Total Phosphorus （TP） were 3.50 mg/L and 0.28 mg/L, higher than the V standards （TN≤2.0 mg/L, TP≤0.2 mg/L） of National Lake Water Quality Standard.