Responses Of Benthic Macro-invertebrates In Different Hydrological Periods Of Daliao River And Naoli River

Formulating scientific and reasonable evaluating indicators is an important way to implement the protection and management of watershed ecological environment system.In terms of the existing watershed ecological health assessment system,compared with the physical and chemical indicators such as hydrology and water environment factors,there is still a big weakness in the setting of assessment indicators reflecting aquatic biodiversity.Benthic animals have good ecological health indicators,and the research on setting evaluation indicators is also lacking.The main reasons include:(1)most watersheds still lack basic information about biodiversity background of long-time series;(2)there are also deficiencies in the research on the corresponding relationship between biodiversity and environmental factors,and the goal setting lacks sufficient support.In such,we selected Daliao River(land sea connection,great human impact)and Naoli River(inland river,little human impact)as the study areas,and carried out a comprehensive investigation on physicochemical factors and benthic macro-invertebrates in three different hydrological periods from 2019 to 2020.The investigated physicochemical factors included 23parameters(water temperature,p H,total nitrogen,total phosphorus,heavy metals,etc.).Based on the investigating data,we analyzed the temporal and spatial differences in the distribution of benthic invertebrates in the two investigated rivers,analyzed the response characteristics between benthic macro-invertebrates and physicochemical factors,and screened benthic indicator species that can be used to evaluate the ecosystem health of Daliao River and Naoli River in different hydrological periods.The main findings include:(1)for Daliao River,in terms of the diversity of benthic invertebrates,14 genera of benthic macro-invertebrates were found during the survey.The numbers of species and dominant species reached the peak in the wet season,while the richness index,evenness index and Shannon Wilson index reached the peak in the normal season.There are many species and abundance of benthic macro-invertebrates in the upper and middle reaches of Daliao River.In terms of physicochemical factors,the content of 23 physicochemical indexes shows an overall trend of high content in wet season and flat season and low content in dry season.The main environmental factors in different hydrological periods are heavy metal elements.The main environmental factors affecting the upstream,middle and downstream are heavy metal manganese(Mn),turbidity and nitrate nitrogen respectively.According to the response analysis of benthic macro-invertebrates distribution and physicochemical factors,the indicator species in the wet,normal and dry season of Daliao River are selected as Anisogammarus,Cipangopaludina and Ephemeridae respectively.(2)For Naoli River,in terms of benthic macro-invertebrates diversity,20 genera of benthic macro-invertebrates were found during the survey.Species peaked in the dry season,dominant species peaked in the wet season,and the highest evenness index and richness index appeared in the dry season.There are many species and abundance of benthic macro-invertebrates in the middle and lower reaches of Naoli River.In terms of physicochemical factors,the content of 11 physicochemical indexes shows an overall trend of high content in wet season and flat season and low content in dry season.The main environmental factors in the wet,normal and dry season are water depth,turbidity and conductivity,and the main environmental factors in the upstream,middle and downstream are water pressure,conductivity and chlorophyll respectively.Through the response analysis of benthic animal distribution and physicochemical factors,the benthic indicator species in the wet,normal and dry season are Radiuauricularia,Tipulasp and Erpobdellaoctoculata respectively.The findings of this study not only enrich the background data of biodiversity in the study area and makes up for the lack of research on benthic indicator species in the Northeast basin,but also provide a demonstration for research on selectiong benthic indicator species in other river basins.