The Community Structure And Water Quality Evaluation Of Macrobenthos In The Pan-prone Area Of ??Lake Taihu

The seasonal surveys on the macrozoobenthos were conducted to investigate the community structure and its major driving environmental factors in the black water cluster(BWC)areas of Taihu Lake during August 2015 and May 2016.The spatio-temporal variations of species composition and biomass were analyzed,and the relationship between community characteristics and environmental factors were discussed.Furthermore,the water quality of the BWC areas were evaluated by using Shannon-Weaver index,Goodnight-Whitley index,Biology Pollution index and Biotic index.The main results were as following:1.Total of 58 macrozoobenthos species were identified,which including 28 species(48.26%of total)of Annelid,17 species(29.31%of total)of Molluscs,12 species(20.69%of total)of Arthropods and 1 species(1.72%)of others.The species number was highest(43 species)in autumn,and lowest(37 species)in winter.In the spatial distribution,the species number in Wuxi harbor(42 species)was the highest,and lowest(19 species)in Xiaoxi harbor.The common species were Limnodrilus hoffmeisteri,Tubifex tubifex,Branchiura sowerbyi,Tanypus punctipennis and Microchironomus tener.2.The average density of macrozoobenthos in the BWC areas of Taihu Lake was(4015.17±447.39 ind/m2).The density of macrozoobenthos in summer was the highest(5826.33± 1373.26 ind/m2),while which in spring was the lowest(1958.83±256.32 ind/m2).There were no significant differences between different seasons.The density of macrozoobenthos in Dapu harbor was the highest(10938.78± 2470.86 ind/m2),while which in Wangyu River was the lowest(713.44 ± 124.15 ind/m2).There were significant difference between different sectors.3.The average biomass of macrozoobenthos in the BWC areas of Taihu Lake was(66.74 ± 12.23 g/m2).The biomass of macrozoobenthos in summer was the highest(117.88± 1 g/m2),while which in autumn was the lowest(37.48± 10.46 g/m2),there were no significant difference between the seasons.The biomass of macrozoobenthos in Dapu harbor was the highest(177.07±63.98 g/m2),while which in Wangyu River was the lowest(16.38±8.34 g/m2),ant there were significant difference between different areas.4.Eight dominant species were defined by using the index of relative importance(IRI>1000)in the studying areas,including Limnodrilus hoffmeisteri,Tubifex tubifex,Branchiura sowerbyi,Limnodrilus grandisetosus,Bellamya aeruginosa,Corbicula fluminea,Tanypus punctipennis and Propsilocerus akamusi.5.The macrozoobenthos only can survive in the sediment within the depth of 45 centimeter,and there were significant difference between the macrozoobenthos community in the vertical distribution.In the studying areas,Hirudinea and Crustacea could only be found in the depth lesser than 10 centimeters,and Polychaeta and Mollusc could be found in the depth from 0 to 20 centimeters.Most macrozoobenthos were distributed in the surface of the sediment(0?20 cm).The number of macrozoobenthos decrease gradually with the increase of depth.The most widely distributed species were Chironomidea and Oligochaeta.6.With the Pearson correlation and RDA analysis,the primary environment factors which affected the macrozoobenthos community and its distribution were water temperature,secchi depth,pH,dissolved oxygen,salinity and conductivity.7.The water quality were assessed by using Shannon-Weaver index,Goodnight-Whitley index,Biology Pollution index and Biotic index.The results showed that the water quality in the BWC areas of Taihu Lake were moderately polluted,and the water quality in summer was the worst in the year.