Relationship Between Macrobenthos Community Structure And Environmental Factors In Rivers And Lakes In Dongguan And Their Water Quality Evaluation

River Basin is the cradle and birthplace of human civilization and the main natural space for the harmonious coexistence of man and nature.In recent years,with the continuous enhancement of human disturbance,the water quality has deteriorated seriously,the aquatic biodiversity has decreased sharply,and the watershed ecosystem has been irreversibly damaged.In order to reveal the physical and chemical properties of water environment,the characteristics of Macrobenthos Community and spatial distribution,identify the key environmental factors affecting the structure of Macrobenthos Community,and scientifically evaluate the health status of the watershed,this study takes the lower reaches of Dongjiang River and delta river network,East diversion canal,Shima River,Henggang reservoir,Tongsha reservoir,songmushan reservoir,Huayang lake Taking Yantian reservoir and other key rivers and lakes as the research object,the samples of macrobenthos and water quality indicators were collected and identified from November to December 2021(dry season).The main research results are as follows:(1)The community of Macrobenthos in rivers and lakes in Dongguan is mainly composed of molluscs,arthropods and annelids.A total of 1715 Macrobenthos were collected,belonging to 40 taxons,27 families,3 phyla,8 classes,15 orders,mainly including 16 species,13 families,3 classes,6 orders of molluscs;18 species,12 families,7 orders,2 classes of arthropods;There are 6 species of annelids in 4 families,2 orders,3classes.The dominant species in the whole study area are Parafossarulus sinensisl and Limnodrilus sp.Other common Nephtys sp.,Bellamya aeruginosa,Pomacea canaliculata,Semisulcospira cancellata,Corbicula largillierti and Palaemon modestus.The species change trend is Shima River>East diversion canal>lower reaches of Dongjiang River and delta river network area>lakes and reservoirs.(2)The spatial distribution of macrobenthos communities in the study area is quite different.The density of Shima River is the best,1861.89 ind/m~2,songmushan reservoir is the second,866.67 ind/m~2,and Yantian reservoir is the worst,103.71 ind/m~2;The biomass of Shima River is the best,628.63 g/m~2,followed by the East diversion canal,344.38 g/m~2,and Yantian reservoir is the worst,15.43 g/m~2.(3)The results of canonical correspondence analysis(CCA)showed that the main environmental factors affecting the community structure of macrobenthos were Total Phosphorus,Total Nitrogen,Permanganate Index,Turbidity and Salinity,among which Total Phosphorus and Turbidity were the environmental factors that had a significant impact on the community structure distribution of macrobenthos(P<0.05).(4)Hilsenhohff index,bmwp index,biological pollution index(BPI)and comprehensive pollution index are used to evaluate the water quality health of rivers and lakes in Dongguan.The overall average water quality is not optimistic.The results of this study can provide a reference basis for the establishment of key river and lake ecological database in Dongguan and the scientific protection of watershed ecosystem.