Community Structure Of River Benthic Macroinvertebrates And River Health Assessment In Jiangsu Province

The rivers and lakes in Jiangsu Province,as well as in Yangtze River Delta,have been seriously polluted with the rapid development of economy,population increase,rapid urbanization and industrialization over the past 40 years.Currently,with the aim shift of water environmental management from chemical water quality to ecological quality in terms of the integration of chemical,physical and biological condition,we must build the sound biological assessment criteria for rivers of Jiangsu Province in order to realize the new aim.Of which the priority is to define the objective indicators and related thresholds of reference condition for Jiangsu river health assessment.Therefore,in the thesis,we aimed to explore the distribution pattern of river benthic macroinvertebrates and the key drivers,then to establish the chemical and habitat thresholds for defining the reference condition for non-navigational rivers in Jiangsu province,and finally to build a benthic index of biotic integrity to assess the river health.We expected our results to improve the practice of river health assessment in environmental management and the aquatic biodiversity conservation in Jiangsu province as well as Yangtze River Delta.Our major results are as follows:In order to understand the macroinvertebrate diversity in relation to the environmental variables,we conduct a survey in April 2017 on the physical and chemical factors,habitats and macroinvertebrates from 31 sampling sites in the Yangtze River reach of Jiangsu Province.In terms of water quality and habitat quality,it showed an obviously increase of TN,TP,CODMn and salinity from Nanjing down to Nantong,with an exception of TP highest at Jiangyin.In addition,the habitat quality showed that Jiangyin was the most impacted one by human and factory activity,while Nanjing was of the longest bank stabilization among four reaches.ANOVA results showed that all the measured chemical and habitat variables except dissolved oxygen and conductivity differed significantly among reaches.In terms of macroinvertebrate,we identified a total of 60 taxa belonging to 3 phyla,7 classes,17 orders and 35 families.The dominant group is arthropods and mollusks and the dominant taxon is Limnodrilus sp.The Dentinphtys glabra,originally found in the estuary area,has become the most common polychaete species from the Nanjing to the Nantong section.The species richness and Shannon diversity of the Zhenjiang section were the highest,31 and 1.71,respectively,followed by the Jiangyin section.The species richness and Shannon diversity of the Nanjing section were 18 and 1.04,respectively.Canonical Correspondence Analysis(CCA)indicates that water pollution,degradation or disappearance of suitable habitats,and shipping are the main influencing factors for the compositional changes of benthic communities in the mainstream of the Yangtze River in Jiangsu Province.The distribution pattern of benthic zoobenthos in the mainstream of the Yangtze River is obviously affected by human activities,and measures such as water pollution control and habitat restoration contribute to the restoration and restoration of benthic diversity.In order to explore to the distribution pattern of river macroinvertebrates and build a IBI for river health assessment in Jiangsu province,we conducted a survey in November 2016 on 179 sites of non-navigable rivers in Jiangsu Province.We identified a total of 102 taxa belonging to 3 phyla,6 classes,17 orders and 53 families.The dominant species were Caridina denticulata,Limnodrilus sp.,Bellamya aeruginosa and Radix swinhoei,with the values of 0.29,0.23,0.22 and 0.15,respectively.Canonical Correspondence Analysis(CCA)indicated that CODMn and NO3--N were the main factors constraining the composition change of benthic communities.Threshold Indicator Taxa Analysis(TITAN)identified the macroinvertebrate composition change thresholds in response to the gradients of four environmental variables:TP?0.185 mg/L,TN<2.27 mg/L,CODMN?4.2 mg/L and HQI?70,respectively.We in turn applied the four thresholds to determine the reference condition for the establishment of benthic index of biotic integrity(B-IBI)which resulted in six sites as the reference sites.We then step by step examine the distribution range,Pearson's analysis,cluster analysis and student T test on 43 candidate metrics,and finally we had the B-IBI composed of six metrics in terms of the total taxa richness,taxa richness of Crustaceans and Mollusks Gastropods%,predator%,taxa richness of collector-gatherers and BMWP.We scaled each metrics using the ratio to the distribution range of each selected metric,and then the 75%quantile of B-IBI value in six reference sites was used as the benchmark for the boundary classification of the health assessment with the excellent class,B-IBI>97;health,72-97;moderate,48-72;poor,24-48;bad,B-IBI<24.Among the 179 sampling sites 2 sites were excellent,8 sites were health 76 sites were moderate,71 sites were poor and 22 sites were bad.In addition,the B-IBI was highly correlated with TN,TP,and also positively correlated with HQI index.Our results highlight the perspective of B-IBI in rivers health assessment and suggest the integrative use of microbes,plankton,fish in a comprehensive assessment of river ecological health assessment since the response of different organism to stressors may vary greatly.