| Aquatic ecosystem is important material source for human production and is significant habitat for aquatic organism,keeping water ecological health is a prerequisite to realize the ecological protection and high-quality development of the watershed.Based on the scientific analysis of the temporal and spatial characteristics of aquatic community structure and its change mechanism,how to establish the river water ecological health assessment by coupling with the characteristics of aquatic community structure has become a frontier and hot issue for maintaining the river aquatic ecological health.As the largest tributary of the Yellow River,Weihe River is the river of life in the Guanzhong region of Shaanxi province,the ecological and environmental problems of Weihe River are representative in the basin.Thus scientifically analyse aquatic community seasonal dynamics and accurately evaluate water ecological health of Weihe River basin not only is the key to improve the function of water ecosystem of Weihe river basin,but also has an important guiding role for the construction of the happy Yellow River.Therefore,the Weihe River Basin is selected as a field experimental watershed.Based on field surveys and sampling in spring,summer,autumn and winter,GIS analysis and difference analysis were used to identify the spatial-temporal dynamics characteristics of aquatic communities,and canonical correspondence analysis(CCA)& redundancy analysis(RDA)was used to reveal the driving factors of the spatial-temporal variation of aquatic communities,and analytic hierarchy process(AHP)and biological index method were adopted to construct the water ecosystem health evaluation system to analyze the water ecosystem health status in the Weihe River Basin.The dissertation mainly achieved the following main conclusions:1.We illustrated the characteristics of aquatic community structure such as plankton,attached algae,fish and benthic macroinvertebrate in Weihe River basin,and the phytoplankton and attached algae have 189 and 169 species or varieties,respectively,with Bacillariophyta species accounting for the biggest,and 79 kinds of zooplankton,with the highest proportion of Rotifer species,and there are 53 species of fish,with Cyprinidae accounted for the highest and there are 215 species of benthic macroinvertebrates,among which the insecta species are dominant.we identified the active distribution area of benthic macroinvertebrate community in the riverbed sediments of Weihe River Basin is the depth of0-30 cm,among which the widespread species was chironomidae larvae.It deepened our understanding of the basic research on the vertical spatial changes of aquatic community in the Weihe River Basin.2.We analyzed the seasonal dynamics characteristics of aquatic communities in the Weihe River basin.For example,the species number of aquatic biotic in summer increased by49.6% compared with winter,and the species number in spring decreased by 21.9% compared with autumn.We discussed the response relationship between the dynamics of aquatic community structure and the change of environmental factors.Meanwhile,the dynamics law and response mechanism of aquatic communities are found.the environmental factors including p H,dissolved oxygen,ammonia nitrogen,total nitrogen and total phosphorus had obvious influence on the dynamics of aquatic communities,and p H,total nitrogen and total phosphorus significantly drived the population changes of Cobitidae,attached algae,and protozoa in spring,and the Dissolved oxygen significantly affected the changes of Rotifer population in winter,while ammonia nitrogen significantly affected the population structure of Bacillariophyta and Chlorophyta in summer.We revealed the effects of spatial differences of hydrological factors and seasonal change of physico-chemical factors on species composition,biological density and biomass of aquatic community.3.It was indicated that the spatial-temporal variation characteristics of aquatic biodiversity index and biological index.For example,the biodiversity index in summer and autumn was 8.26% higher than winter and spring,and the biodiversity index in Weihe River was 6.89% higher than Jinghe River and Beiluohe River.Based on two kinds of index we constructed the comprehensive evaluation index of water quality(CEWI)of Weihe River basin.A new method to comprehensively evaluate the water environment quality was developed to reveal the water quality situation of Weihe River basin,and the results showed that the overall state of water quality was middle pollution in the Weihe River Basin,and CEWI model reduced the error of single aquatic organism or single index to evaluate water environmental quality in weihe River Basin.This would help to broadly understand to the water environment condition and the contaminated degree of Weihe River basin.4.Based on the multi-group biological integrity index(m-IBI),the water ecological health evaluation system was established to evaluate the aquatic ecological status of Weihe River basin was healthy,and analyze and clarify the variation characteristics and response mechanism of water ecological heal that different time scale in Weihe River basin,for example,ammonia nitrogen and total nitrogen had significant effects on biological integrity.Meanwhile,the reliability of the water ecological health evaluation system based on the multi-group biological integrity index was compared and analyzed.and the correlation coefficient between the evaluation result of m-IBI with single biological integrity index(s-IBI)was greater than 80%,and the agreement degree between the evaluation result of m-IBI with RHCI was more than 87%.This will help to perfect the evaluation method of water ecological health and improved the accuracy of evaluation results in Weihe River Basin.This paper comprehensively investigated the community structure of aquatic organisms from the temporal and spatial scales,and systematically revealed the driving relationship and response mechanism between aquatic organisms and environment,and comprehensively evaluated the health status of the Weihe River basin,and play an important the role of science and technology support in the implementation of the major national strategy “the ecological protection and high quality development of the Yellow River basin”... |
