Researches On Aquatic Biological Community Structure And Diversity Of The Lakes In Jiangsu Province

With the rapid population growth and economic development,lake resources were over exploited,and a number of ecological environmental problems generated.As one of the ecological disasters,cyanobacteria bloom is threatening the health of human and animal.Jiangsu province is one of the most developed provinces in China.The lakes in Jiangsu Province are suffering from serious environmental problems,such as eutrophication,cyanobacteria bloom,and the loss of the biodiversity.The aquatic communities(such as benthic macroinvertebrates and phytoplankton)are not only important elements of the aquatic ecosystem,but also important ecological indicators to understand and monitor changes of environment.Due to the huge environmental pressure,the structure and diversity of aquatic organisms are changing.Although there were a lot of researches focusing on water environmental parameters in eutrophic lakes,ecological effects of environmental pollution measurements were always ignored.A number of studies were focused on phytoplankton and microcystin in lakes.But these studies mainly focused on bioaccumulation and single species toxicity of microcystin;but the impacts of MC-LR on aquatic communities in lakes have not been examined to date.In this study,macrobenthic community structure and diversity of 16 lakes in the Jiangsu Province were investigated to assess whether synthesized trophic state index for eutrophications can response real ecological health.The aquatic community structure and diversity of two typical lakes(Tai Lake and Ge Lake)in Jiangsu province were evaluated,and the main ecological factors affecting the aquatic community structure and diversity were discussed.The effects of derivatives of microcystins on aquatic community structure and diversity were explored,and the measures for protection of aquatic biodiversity were put forward.The main conclusions are as follows:1.In spring and autumn of 2012,macrobenthic community structure and diversity were surveyed in the 16 lakes in Jiangsu province.Results of the present study demonstrated that the 16 lakes in Jiangsu province were mostly eutrophicsupereutrophic lakes.Significant change has been found in the structure of macrobenthic communities in the lakes.The community structure was relatively simple and tends to be homogeneous.From the perspective of time,eutrophication was the main factor that affected the structure and diversity of macrobenthic communities.From the spatial pattern,aquatic macrophyte and hydrological conditions were important factors affecting the structure and diversity of macrobenthic communities in the 16 lakes.Therefore,it is urgent to control the pollutants into lakes and restore aquatic macrophyte for protecting the aquatic ecosystems.2.In spring and autumn from 2008 to 2012,the structure and diversity of the benthic macroinvertebrate in Ge Lake were surveyed.Results demonstrated that the diversity of macrobenthic community decreased,compared with the historical reports.The sensitive and clean water species disappeared,and the density of the pollutants tolerant taxa,such as oligochaete worm,Limnodrilus hoffmeisteri increased.The macrobenthic communities in Ge Lake exhibited a greatly lesser diversity,compared to that reported historically.Permanganate index,total nitrogen,and synthesized trophic state index were the main factors influencing macrobenthos structure and diversity.Besides,the severity of effects of human activities on Ge Lake,such as large-sclae fish net-pen cultures,hydrophytic vegetation destruction,were important factors influence factors affecting the structure and the diversity of the macrobenthic.Therefore,eco-restoration projects,such that to restore the benthic invertebrate community to previous conditions,would be necessary to control and reduce the organic pollutants and inorganic nutrients into Ge Lake.3.In spring and autumn from 2011 to 2013,we conducted a survey of Tai lake to examine the effects of microcystine and other pollutants on marcobenthic community structure and diversity.Results showed that macrobenthic community structure and diversity in Tai Lake had changed through time,compared to that reported historically.In the 1960s when the lake was rich in aquatic plants and grass,there were a large number of Corbicula fluminea,Viviparus quadratus and few oligochaetes.At present,the diversity of the macro-benthic decreased,and the pollutant tolerant specie,oligochaeta became the predominant species in the Tai Lake.The relationships between macrobenthic metrics(Shannon-Wiener and Pielou)and environmental variables showed that community structure and spatial patterns of macrobenthos in Tai Lake were significantly influenced by chemical oxygen demand(CODCr),biochemical oxygen demand(BOD5),lead(Pb),and microcystin-LR(L for leucine and R for arginine).Macrobenthic community indictors(Shannon-Wiener index and Pielou evenness)in Tai Lake increased over the course of our study from 2011 to 2013.This may be occurring because the local government increased efforts to monitor and reduce environmental pollutants entering into Tai Lake after the drinking water crisis in the summer of 2007.Our findings provide critical information that could help managers and policymakers assess and modify ecological restoration practices.4.Phytoplankton community structure and water quality parameters were monthly investigated in Tai Lake between January and December of 2013 in our study.Results of the present study suggested that the density of phytoplankton community in Tai Lake was relatively high and its diversity was low.From the time point of view,the density of phytoplankton community observed the highest density in December,followed by June.The optimal conditions,such as strong illumination and the low water level might stimulate a large number of the dormant phytoplankton,which germinated and grow in the lake rapidly.The primary pollutant was total nitrogen in Tai Lake,followed by total phosphorus and chemical oxygen demand.Chemical oxygen demand,chlorophyll a,synthesized trophic state index,and MC-LR were main factors that influenced phytoplankton community structure in Tai Lake.Therefore,it is very important to control and decrease pollutants into Tai Lake to restore ecological functions.