Study On Macroinvertebrates Community And Bioassessment For Water Quality Of Yili River, Xinjiang

Macroinvertebrates are an important part of river ecosystem because of their aboundance and position as “middleman” in the aquatic food chain,macroinvertebrates play a critical role in the balance and natural flow of energy and nutrients.Different species of macroinvertebrates have different sensitivity to water quality,so they also can be used as an indicator to evaluate the health status of river.Research on environmental factors of macroinvertebrates is still a hotspot.By now,the researches on macroinvertebrates in China are mainly concentrated on the coastal areas,and the research on the western regions such as Xinjiang is relatively rare,especially the international river such as Yili River.In this study,the macroinvertebrates of Yili River in Xinjiang was selected as the study object,sampled from July to August in 2014 and July to August in 2015 respectively.Meanwhile,environmental index were measuredto answer these scientific problems:1)What is the status of macroinvertebrate community and its main influencing factors in Yili River,Xinjiang?2)What is the status of functional feeding groups and its main environmental factors of the Yili River in Xinjiang?3)How does habitat affect macroinvertebrate community?4)What is the river health status of the Yili River,Xinjiang? Which bioassessment index is more suitable for biological evaluation of water quality in Yili River? The main conclusions are as follows:(1)During the study period,a total of 19735 macroinvertebrates were collected from Yili River,Xinjiang,belonging to 81 taxa,39 families and 11 orders.Among them,aquatic insects,mollusks and oligochaetes respectively accounted for 93.8%,2.5% and 3.7%.Cinygmula sp.and Pelopia sp.were the dominant species.The average density of macroinvertebrates was 1385.2 ind./ m2,with aquatic insects contributing the most.The macroinvertebrate community of Yili River had higher diversity,but there were significant differences among the different sampling points.Flow velocity,conductivity,water temperature and elevation were the main factors affecting the distribution of macroinvertebrates community in Yili River.(2)The Functional Feeding Groups of macroinvertebrates in Kunnes River,the third major tributary of Yili River,is in a healthy state.While the Functional Feeding Groups of macroinvertebrates in Kashi River,the second major tributary Yili River,is severely degraded due to human activities,with Filter-collectors and Shredders disappeared.The most important environmental factors influencing filter-collectorswere water temperature,flow velocity,dissolved oxygen and pH.The scrapers were mainly affected by the conductivity,altitude,flow velocity,water temperature and the sediment with 16-64 mm diameter.The main environmental factors affecting gather-collectors were dissolved oxygen,altitude,water temperature and the substrate which the diameter less than 1mm.The main environmental factors affecting shredders were conductivity,altitude and water temperature.The predators were mainly affected by organic matter,conductivity,water temperature and dissolved oxygen.(3)The community structure characteristics of macroinvertebrates in four habitats: natural habitat,damaged habitat,under-dam habitat and protected area,were compared and analyzed.The results showed that natural habitats had the highest species richness,the number of dominant species,the EPT richness,the density and species diversity,and the lowest habitat in under-dam habitat.The community structure of macroinvertebrates in protected area was better than that in damaged habitat and under-dam habitat.(4)The ecosystem health of Yili river was evaluated based on macroinvertebrates.The results showed that the health of aquatic ecosystem of Yili was at a high level as a whole.But health quality rating among different sampling sites are quite different.According to the results,the sites of Kashi River which were in the “healthy” and “subhealthy” conditions accounted for 35.6%,and the percentage of the “poor” and “very poor” sites was 20.0%.While the sites of Kunnes River which were in the “healthy” and “subhealthy” conditions accounted for 84.0%,and there were no sites in the “poor” and “very poor” conditions.There was a significant liner relationship between the evaluation of these five biology index,except for the relationships including Pielou index vs.Margalef,Pielou index vs.BMWP score system.However,the evaluation results of Pielou and ASPT score system are slightly inferior sensitivity.