Community Structure Of Macrozoobenthos And Its Response To Environmental Factors In Heihe River Basin

In recent years,due to the dual interference of natural factors and human activities,the physical,chemical and biological processes of the original river ecosystem in different time and space scales have changed to varying degrees,which has changed the hydrological situation of the river basin,river sediment transport,water quality and health,resulting in the sharp decline of the river biodiversity,the weakening of the river ecological conditions and service functions,etc.Macrozoobenthos as an indispensable and important member of the river ecosystem community,playing a connecting role in the material cycle and energy flow of the water ecosystem,and have a good indicator role in the environmental change.They are widely used in water ecological monitoring and water ecosystem health assessment.To study the response relationship between the community structure of macrozoobenthos and its dynamic changes and environmental factors is not only to help understand the material cycle and energy flow of water ecosystem,but also to provide theoretical support for the protection and restoration of water ecosystem.Based on this,this paper conducts an ecological investigation on the dynamic changes of macrozoobenthos and water environment in the upper and middle reaches of Heihe River,and studies the response of macrozoobenthos community structure and biodiversity to water environment,so as to provide help for understanding the material circulation,energy flow and information transmission of water ecosystem in Heihe River Basin,as well as provide scientific data support and reference for water environment protection,river ecological restoration and sustainable utilization of water resources.The main results are summarized as follows:?1?The community structure and biodiversity of macrozoobenthos in the upper and middle reaches of Heihe River are generally good,species composition is relatively complex,and the main stream in the middle reaches is significantly richer than the tributaries in the upper reaches,showing significant spatial and regional differences.The results show that:1308 macrozoobenthos were collected and 43 species were identified,belonging to 3 phyla,7 classes,14 orders and 23 families.The dominant species in the whole study area are the following 6 species,which are:Tipulidae,Damselfly,Argyroneta,Radixauricularia,Suecinea sp.,Gyraulusalbus.There are significant differences in the distribution of dominant species in different river reaches,the distribution trend of each habitat is the middle main stream?6 species?>the upstream tributary?5 species?.There are obvious spatial heterogeneity in species composition,biomass and biodiversity,in the middle stream is more important than the upper stream;The change trend of macrozoobenthos density of different biota groups was arthropod>mollusc>annelids,the trend of biomass change is molluscs>arthropods>annelids.The similarity of macrozoobenthic community structure at different habitat scales show that:the similarity between the upstream tributary and the upstream tributary,the middle main stream and the middle main stream is high,and there are more species in common;the similarity between the upstream tributary and the middle main stream is low,and there are less species in common;The comparison between the dynamic change of biodiversity index and the trend of species distribution shows that the Shannon Wiener diversity index and Margalef richness index are suitable to reflect the biodiversity of macrozoobenthos in the upper and middle reaches of Heihe River.?2?The health status of water quality was evaluated by macrozoobenthosindex and Carlander biomass index combined with water physical and chemical index and comprehensive pollution index.The results show that:biological evaluation of water quality are basically consistent with those of physical and chemical indexes of water body.The evaluation of theindex index shows that the water quality as a whole is light pollution,the quality of the upstream tributaries is better than that of the main stream in the middle reaches.The Carlander biomass index evaluation shows that the nutritional types of water quality are generally at the mid-nutrition level,the nutrition level of the upstream tributary is lower than that of the middle stream.A variety of physical and chemical indicators are used for water quality evaluation.As for the whole research area,the water quality is classified as class I,class II and class III.According to the comprehensive pollution index evaluation,it is found that the overall water quality is moderately polluted,the upstream tributaries are mildly polluted,and the middle reaches of the mainstream are moderately polluted.On the whole,the water quality is in good health.?3?Based on the analysis of the correlation matrix between benthic animals and environmental factors in different groups,and combined with RDA analysis showed that the main environmental factors affecting the structure and biodiversity of macrozoobenthos communities in the upper and middle reaches of the Heihe River are BOD₅,WT,EC,DO,TDS,COD_Mn and salinity.