Zooplankton Communities And Bio-assessment Of Five Rivers In The Outskirts Unit Of Southwest Shanghai

To evaluate the restoration from the contaminative water condition of five rivers, which are Wuchaogang River,Zhoujiabang River,Shuichengluzhoujiabang River, Caoyanghuanbang River and Liwa River in the outskirts unit of southwest Shanghai, the investigations of the spatial variations of zooplankton community structure, biomass and eleven chemical and physical parameters were undertaken from February to April,2007.The water quality of these rivers were assessed by both biological methods(qualitative and quantitative analyses of zooplankton community and bio-diversity indexes)and chemical methods(Integrated pollution index and Chemical evaluation index),respectively.The main research results are as follows:1)Forty-five species of zooplankton were identified,among which there were 31 Rotifer species,8 Cladocera species and 6 Copepoda species with a ratio of 68.9%, 17.8%and 13.3%,respectively.Species composition of zooplankton was different in different seasons.But Rotifer was dominant species in four seasons.2)The dominant species of the zooplankton were Filinia minuta,Bosmina longirostris and Mesocyclops leuckarti in all year;Brachionus calyciflorus in spring, summer and autumn;Rotaria neptumia in spring;Daphnia carinata in summer Asplanchna priodonta and D.pulexin winter,respectively.3)The results of the horizontal distribution of the zooplankton standing crops shows that the most high abundance and biomass of zooplankton was at point 6 which were 12379 ind./L and 4.366mg/L,respectively.But there were just seven species of zooplankton at this sampling site.The zooplankton standing crops of point 2 where twenty-five species were found were scarcely less than point 6.At point 7,the abundance and biomass of zooplankton were the lowest which were 718 ind./L and 0.619mg/L,respectively.4)The results of the evaluating by the Integrated pollution index(PI)and Chemical evaluation index(Pb/n)showed that the water of Wuchaogang River and Zhoujiabang River was extremely serious polluted.The water quality of point 9 was subjected to heavy pollution and the water quality of the rest sampling sites was light polluted.5)Annual average Shannon-Weaver diversity index of zooplankton ranged from 0.254 to 1.510 and the Simpson diversity index ranged from 1.107 to 2.741 while the Margalef diversity index ranged from 0.214 to 1.109.Based on the assessment of the water quality by the three biodiversity indices,it appeared that point 2,point 8 and point 10 wereαtype of medium pollution while the point 1 wasβtype of medium pollution.The water quality of the rest six sampling sites were subjected to multi-polluted type.6)The principle component analysis classified the 13 physico-chemical-bio parameters into three groups:in the first component is loaded with the majority of the physico-chemical parameters,such as DO,EC,TDS,NH₃-N,PO4,NO₂ and BOD; the second component is loaded with bio-diversity index while the third component shows NO₃.By the method of regression analysis we got the score of principal component of the ten sampling sites,then cluster analysis grouped ten sampling sites into three clusters of similar water quality characteristics,divided the ten sampling sites into A,B and C three types which standed for oligosaprobic～β-mesosaprobic,β-mesosaprobic～α-mesaprobic and multi-polluted.In the first group,Wuchaogang River(point 1 and point 2)and Zhoujiabang River(point 3 and point 4)were identified in a cluster which the water quality was C degree;In the second group, Liwa River(point 9 and point 10)and point 7 were identified in a cluster which the water quality was B degree and in the third group,Shuichengluzhoujiabang River (point 5 and point 6)and point 8 were identified in a cluster which the water quality was A degree. 7)Based on the integrative evaluation of the biological and the chemical methods,it was suggested that the water quality of the five rivers can be sorted fromαtype of medium pollution to multi-polluted type.Meanwhile,our study indicates that the five rivers which used to be were malodorous and black rivers before artificially integrative treatment had recovered gradually,however,its aquatic ecosystems still has remained unstable,which the zooplankton communities were strongly affected by contaminative water and the species and components were shown as relatively simple. It war suggested that management has to put more efforts for the river restoration in order to establish the aquatic biodiversity and the healthy and self-management system.