The Relationship Between Macrobenthic Community Structure And Environmental Factors In The Gongnaisi River,Xinjiang

Macrobenthos are groups of aquatic invertebrates that live at the bottom of water bodies rich in organic matter.They are large in number,widely distributed and rich in taxa,which play an important part of the river ecosystem.The life activities of macrobenthos directly or indirectly affect the integrity of the structure and function of the aquatic ecosystem.At the same time,they also play a key role in the material transportation,energy flow and information transmission in the river ecosystem.In response to the practical needs of researching and protecting natural river ecosystems,this paper explored the ecological conditions of the upper reaches of the Gongnaisi River in Xinjiang.Field experiments were carried out in October 2018(dry season)and June 2019(wet season).We measured environmental factor data and collect macrobenthic samples at fixed points.By comparing and analyzing the differences in macrobenthic species composition,functional feeding groups and life-form classifications between the two periods,and their relationship with environmental factors,the health status of the Gongnaisi River was judged according to the macrobenthic biological index.The results of this research can not only provide basic data for the ecological protection of the Gongnaisi River and follow-up related research,but also supplement the ecological research results of the Yili River,and have certain reference significance for the development of related research on the Yili River.The research results are as follows:(1)We collected 40 species of macrobenthos,belonging to 3 phyla,4 classes,8orders,27 families.The main species were arthropods.In the dry season,there are an average of 19 species of macrobenthos at each sampling site,with an average density of 1281±548 ind·m^-2;in the wet season,there are an average of 24 species of macrobenthos at each sampling site,with an average density of 2300±585 ind·m^-2.On the whole,the density of macrobenthos at each sampling point in the dry season is lower than that in the wet season.Orthocladiinae spp.and Tanytansini sp.,Baeits sp.,Ameletus sp.and Cheilotrichia sp.are the dominant groups of macrobenthos in the Gongnaisi River.There are significant differences in the macrobenthic community structure of Gongnaisi River between the dry and wet seasons.The T-test results show that the biological density and species richness of the macrobenthic community in the wet season are significantly higher than those in the dry season(P<0.05).However,there was no significant difference in the biodiversity index and Pielou evenness index of macrobenthos between these two seasons(P>0.05).(2)Analyzing the functional feeding groups of macrobenthos in the Gongnaisi River,the study found that there are five functional feeding groups of predators,gather collectors,scrapers,filter collectors and shredders.And the collector is mainly group in both dry and wet seasons.The relative abundances are 40.21%and 73.01%respectively.In terms of life types,There are five types of macrobenthos in the Gongnaisi River:clingers,sprawlers,climbers,burrowers and swimmers.The relative abundance of clingers is 43.20%in dry season,which is highest.And the relative abundance of sprawlers is 57.53%in wet season,which is highest.(3)There are significant differences in environmental factors between the dry and wet periods of the Gongnaisi River.The flow rate and water temperature are significantly lower in the dry period than in the wet period(P<0.01).The dissolved oxygen,electrical conductivity,total solid solubility and p H are significantly higher in the dry period than in the rich period.Water period(P<0.01).After a canonical correspondence analysis between macrobenthos and environmental factors,it is found that the p H and water temperature in the dry season play a leading role in the distribution of macrobenthos,and the environmental factors that play a leading role in the wet season are water temperature and electrical conductivity.Water temperature is a key environmental factor affecting the changes of macrobenthic communities in the Gongnaisi River in different periods.(4)The overall health of the upper reaches of the Gongnaisi River is relatively good.It was found that among all the samples,the samples with“sub-healthy”water quality status accounted for the highest proportion,accounting for 42.59%;followed by the“healthy”status,accounting for 37.96%.Margalef index and ASPT index are poor in sensitivity and are not suitable for biological evaluation of the upper reaches of the Gongnais River.Therefore,this study thinks that Shannon-Wiener index,Pielou index,BI index,and BMWP index are more suitable for biological evaluation of water quality in this area.