| Macroinvertebrates plays a very important role in freshwater ecosystems and food chain of river ecosystems.Macroinvertebrates are of great significance to the processes of material cycling,pollutant migration and transformation in river ecosystems,reflecting long-term changes in river ecosystems.The Weihe River Basin was regarded as the research area,and macroinvertebrates were regarded as the research project in this study.In June 2017,September 2017,January 2018 and April 2018,macroinvertebrates,plankton,periphytic algae and water samples were collected in 55 samples of the main stream and tributaries in the Weihe River Basin.The spatial and temporal distribution characteristics of macroinvertebrates in the Weihe River Basin were analyzed by means of laboratory identification,statistical analysis of data,difference test and comparative analysis.Analyzing the effect of physical,chemical and biological factors(including water temperature,total nitrogen(TN),total phosphorus(TP),dissolved oxygen(DO),plankton biomass,and periphytic algae biomass)on the distribution of large invertebrates using Canonical Correspondence Analysis(CCA).The temporal and spatial characteristics of water quality in the Weihe River Basin were evaluated,using the biological index evaluation method.The conclusions were summarized in this following:1)The spatial and temporal pattern of macroinvertebrates was identified in the Weihe River Basin.D-type net and Surber net(30 * 30 cm,250 ?m)were used for qualitative and quantitative sample of macroinvertebrates in each sampling point.The composition of species,density,biomass,biological index and spatial and temporal patterns of macroinvertebrate communities was analysed by identification,difference analysis and biological index calculation in the Weihe River Basin.The results of this study showed that a total of 208 macroinvertebrate species were collected in spring,summer,autumn and winter,belonging to 7 classes,18 orders and 63 families.These macroinvertebrates include 3 categories: Annelida,Mollusca and Arthopoda.The species composition of macroinvertebrate communities had obvious seasonal variation in the Weihe River Basin.The highest number of species and density in summer,and the lowest number of species in winter.Owing to high temperatures and stable habitats in summer,which is benfit to species reproduction and survive.During the investigation,it was found that the dominant species were mainly tolerant species including Tubificidae and Chironomidae,accounting for 75% of the dominant species,with a wide range of distribution and a high frequency of occurrence in the Weihe River Basin.However,there are few sensitive species such as EPT taxa,which indicates that the water quality of the Weihe River Basin is still not optimistic.The Margalef richness index(D),Pielou evenness index(J)and Shannon-Wiener diversity index(H)of the Jinghe River were highest among the three rivers,indicating that the Jinghe River has the most stable community structure and richest diversity of species.2)The relationship between macroinvertebrates and environmental factors was revealed in this study.Based on the data of environmental factors and the spatial and temporal pattern of community structure,correlation analysis and canonical correspondence analysis(CCA)were used to analyze the effects of environmental factors on macroinvertebrates.The results showed that river width was common influencing factor of macroinvertebrates for 4 seasons.Zooplankton biomass was common influence factor in spring and winter.And periphytic algae biomass was common influence factor in spring and summer.The relationship between macroinvertebrates and environmental factors showed that the most significant factor was physical environmental factors,followed by biological environmental factors and finally chemical environmental factors.The dominant species such as Tubificidae and Chironomidae were affected by water temperature,TN and DO.Due to Tubificidae and Chironomidae were tolerant species,usually at high water temperatures,serious pollution,breeding in areas with high water temperature,serious pollution,and high nitrogen and phosphorus.3)The water quality of the Weihe River Basin was confirmed.The water quality in the Weihe River Basin was evaluated by using Shannon-Wiener index,Simpson index,BMWP index and ASPT index.The evaluation results showed that the water quality of most samples was in a general condition,and there were poor condition and extremely poor condition in the Weihe River Basin.This research showed that the water quality of the Weihe River Basin had improved in recent years,but the overall water quality was in general condition.Mainly due to the prevention and control measures taken by the Shaanxi Provincial Government for water pollution in the Weihe River Basin.Based on biological evaluation of water quality could provide a scientific support for prevention of river pollution and ecological restoration of the Weihe River Basin,and could provide a strong guarantee for achieving high-quality development in the Yellow River Basin. |
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