Distribution Patterns Of Macroinvertebrates And Health Assessment In The Le’an River

Le’an River is a primary tributary of the Rao River and a secondary tributary of Poyang Lake,the largest freshwater lake in China.Le’an River is a typical river affected by mine wastewater.In addition,Le’an River is also affected by industrial and agricultural pollution in surrounding towns,which stresses the ecological health of the river basin.The study on the community characteristics of macroinvertebrates is helpful to maintain the biodiversity and ecosystem stability of Le’an River;Benthic index of biological integrity was built to assess the ecological health status of Le’an River,which can provide research reference for the restoration and management of Le’an River.In May and October 2019,macroinvertebrates and water quality of Le’an River were sampled.Based on the survey data,this study analyzed the structural composition and spatiand temporal distribution of macrobenthic communities in the Le’an River,and identified the key environmental factors.In addition,this paper analyzed the functional feeding groups of macroinvertebrates,and evaluated the status of ecological health of Le’an River water based on feeding function groups,and identified the key environmental factors that affect the feeding function groups;Tolerance value of common macroinvertebrates in Le’an River were preliminary calculated to compare with other regions of China.After building the candidate index system for Le’an River B-IBI,The B-IBI indexes were selected through distribution range test,discriminant ability analysis and correlation analysis to evaluate the the Hydrophytic Ecosystem of le’an River.The main study findings are as follows:1.Structure of macrobenthic community and key environmental factor identification in Le’an River.In May 2019,84 species of macroinvertebrates were collected in Le’an River in Dexing,including 48 classes,36 families;106 species of macroinvertebrates were collected in October,including 47 classes and 34 families;arthropods occupied the main superiority（76.47%in May,69.81%in October）.The biodiversity level of macroinvertebrates in Le’an River was higher and more uniform than that in May.The main environmental factors affecting macroinvertebrates were p H,Ca²⁺,ORP and NH₄+in May;NH₄+,COND,ORP and Depth in October.2.Community structure of macroinvertebrates feeding function groups and identification of key environmental factors in Le’an RiverAccording to the results of the survey of macroinvertebrates feeding function group in Le’an River in May,there were 23 species of collector-gatherers（GC）,41species of predators（PR）,12 scrapers（SC）,8 collector-filterers（FC）and 1 species of shredder（SH）.In the October survey,there were 22 species of collector-gatherers（GC）,54 species of predators（PR）,15 species of scraper（SC）,10 species of collector-filterers（FC）and 1 species of shredder（SH）.In terms of individual number,predators（PR）occupied the maximum numerical advantage,with a relative abundance of 35.20%in May and 39.84%in October.The relative abundance of predators（PR）and scrapers（SC）was higher in October,and the remaining taxa had a higher relative abundance in May.Results of RDA analysis revealed that the major environmental factors which influenced the distribution of macrobenthic feeding function groups in May were dissolved oxygen（DO）,Oxidation-Reduction Potential（ORP）,Electrical Conductivity（EC）and p H;the major environmental factors that influenced the distribution of macrobenthic feeding function groups in October were dissolved oxygen（DO）,p H and water depth（Depth）.3.Calculation of the tolerance value of macroinvertebrates in Le’an RiverThe tolerance values of 44 macroinvertebrates taxa which occurred more than 5times in Le’an River basin were calculated and compared with the same taxa in Liaohe River Basin,Lushan region and eastern China.Among the 44 taxa,tolerance value of the Annelida was between 6 and 9,which could be used as an indicator species for polluted water,such as Glossiphoniidae,Branchiura sowerb and Limnodrilus hoffmeisteri;Taxa getting low tolerance value score including Heptagenia,Corydalidae,Caridina and so on could be used as the indicator species of clean water;the species of Chironominae,labrundinia,Melaniidae,Potamanthidae and Caenidae,which got around 5 points,could be used as indicator species of moderately polluted water.4.B-IBI healthy assessmentThe B-IBI system was built to assess the biological integrity of 28 sampling sites in the Le’an River basin.Results in May revealed that there were 14 sites in"healthy"degree,2 sites in"good"degree,7 sites in"average"degree,4 sites in"poor"degree,and 1 site in"poor"degree.health evaluation results in October showed that there were 9 sampling sites in"good"grade,9 in"average",4 in"poor",and 1 in"poor".In May,half of the sampling sites were in"good"state,and 50%of the sites in October were in"healthy"or"good"state.The health condition of water ecology of Le’an River in May was better compared to that in October.