Analysis Of Temporal And Spatial Heterogeneity Of Macroinvertebrates Community Structure And Assessment Of Biological Integrity In The Huangshui River Basin

Huangshui River is the largest first-class tributary in the upper reaches of the Yellow River Basin.Because it is located at the junction of the Qinghai-Tibet Plateau and the Loess Plateau,it has unique geographical and climatic characteristics.Under the interference of global climate and human activities and many other factors,the water ecological health of Huangshui River Basin has changed.In particular,due to the impact of urban pollution discharge and land use changes around the basin,the survival and reproduction of aquatic organisms in Huangshui River has been greatly threatened.By analyzing the structure and functional feeding groups of macroinvertebrates in Huangshui River Basin,and identifying the key environmental factors affecting them,we can focus on some aspects of the water ecological health of Huangshui River Basin.Using the benthic index of biotic integrity（B-IBI）to evaluate the health status of Huangshui River can provide a certain basis for the health status and provide references for the protection of the biodiversity of Huangshui River.Based on the Huangshui River Basin macroinvertebrates survey data,this paper analyzed the macroinvertebrates community structure characteristics,identified the main environmental factors,and analyzed the distribution differences of macroinvertebrates in Huangshui basin in spring and autumn through Shannon-Wiener index,Margalef index,Simpson index and Pielou index;The analysis of functional feeding groups led to the conclusion that the main environmental factors affecting the functional feeding groups of macroinvertebrates in the Huangshui River Basin.After selecting reference and damaged sites and identifying biological indicators,the Huangshui River Basin Benthic Index of Biotic Integrity（B-IBI）was constructed and the health of the Huangshui River was evaluated.A comprehensive environmental gradient for multiple types of environmental factors were constructed to evaluate the applicability of the benthic index of biotic integrity of Huangshui River.The main results are as follows:（1）Arthropoda has the largest number of macroinvertebrates in the Huangshui River Basin.The number of species,Shannon-Wiener index,Margalef index and Pielou index in autumn were all higher than those in spring,and there were differences in the number of species,Margalef index and Pielou between two seasons.The abundance and diversity of species in the upper reaches are better than those in the middle and lower reaches.Human disturbance in the middle and lower reaches has increased,species abundance and diversity have declined,and tolerant species have also increased.In spring and autumn,the habitat quality of the upper reaches is better,and the sediment particle size is larger,while the concentration of various pollutants in the middle and lower reaches increased,the habitat quality has degraded,and the sediment particle size becomes smaller than the upstream.In autumn,the environmental factors that mainly affect the community structure of macroinvertebrates are EC,TUR,NH₃,TP and Habitat;In spring,EC,TDS,DO,Ca²⁺and Habitat are the main environmental factors affecting macroinvertebrates community structure.（2）There are five species of macroinvertebrates functional feeding groups in the Huangshui River basin,of which collectors has the lagest number in both spring and autumn,while the number of shredders is most different between the two seasons.Based on various parameters of functional feeding groups,the ecosystem attributes of Huangshui River were analyzed,and it was concluded that the habitat stability of Huangshui River in autumn was better than that in spring.In autumn,the main environmental factors affecting the functional feeding groups of macroinvertebrates in the Huangshui River are Na⁺,Cl^-and NO₂^-;In spring,the main factors are substrate particle size,EC and Habitat.（3）By selecting reference and damage sites,conducting range analysis,discriminatory power analysis and Pearson’s correlation analysis of candidate biological indicators.Seven biological indicators,namely family-level abundance,number of Diptera taxa,Margalef index,the number of tolerant taxa,ASPT,collector%and the number of adherents taxa,were selected as indicators for constructing the benthic index of biotic integrity in the Huangshui River basin,the health evaluation standard was obtained:B-IBI≥3.46 is healthy;3.07-3.45 is good;2.69-3.06 is average;2.31-2.68 is poor;B-IBI<2.31 is poor.The evaluation of various sampling points in the Huangshui River Basin shows that the overall ecological health of the Huangshui River is relatively good.And the water ecological health of Huangshui River in autumn is better than that in spring.The benthic index of biotic integrity in Huangshui River Basin has strong correlation with COD_Mn,NH₃,TP and Cl^-.（4）In the process of constructing the comprehensive environmental gradient axis,it was found that TUR contributed the most to the comprehensive pressure gradient axis of salt ions;TN and NH₃ contribute the most to the comprehensive pressure gradient axis of nutrients;Depth makes the greatest contribution to the comprehensive pressure gradient axis of the habitat;EC,SAL,TUR,K⁺,Na⁺,Cl^-,TN,NO₂^-and Habitat are the environmental factors that contributed the most to the comprehensive pressure gradient composed of all environmental factors.Performed principal component analysis on various environmental factors and calculated PCAs values,and performed correlation analysis with biological indicators.Biological indicators that correlate significantly with each pressure gradient axis are mainly those characterising community abundance and tolerance,while those without correlation are mainly biological indicators of relative richness and nutrient structure.