The Characteristics And Biodiversity Of Water Quality On A Section In The Upper Reaches Of The Nenjiang River

The Nenjiang River is an important basin in the Northeast,which affects the economic development of the nearby areas.However,there are few studies on the physical and chemical indicators of water quality and the plankton and sedimentary biological communities in the upper reaches of the Nenjiang River.Therefore,it is imperative to optimize the Nenjiang River water quality monitoring platform.This paper takes a certain section of the upper reaches of the Nenjiang River as the research object,studies the changes in water quality in recent years,studies and compares the conditions of aquatic communities in flood and non-flood periods,and explores the correlation between physical and chemical indicators of water quality and aquatic communities.To provide a certain theoretical basis for the establishment of a water quality monitoring platform containing biological indicators,and to provide a basis for the study of water quality in the Nenjiang River Basin during the flood season and non-flood season.This project collected and tested the actual water quality monitoring data of this section of the Nenjiang River from 2016 to 2020,a total of 21 routine testing items.First,the single-factor evaluation method is used to rate the water quality status every month,and it is found that the water quality status from 2016 to 2020 is up to the standard,but the content of organic pollutants has a tendency to exceed the standard,which needs to be focused on detection;and the water quality status in the flood season is obvious Worse than non-flood seasons.Secondly,combined with the actual water quality monitoring data,the main environmental factors of the section were screened out by principal component analysis methods as COD,COD_Mn,total phosphorus（TP）,and ammonia nitrogen（NH₃-N）.Finally,the selected main environmental factors were analyzed for individual indicators,and it was found that the content of COD and COD_Mnwas increasing year by year,and the content of ammonia nitrogen（NH₃-N）reached the standard,and the trend of increasing year by year was obvious;total phosphorus（TP）was controlled.Better,the content is less year by year.Water samples and sediment samples will be collected during the flood season（June）and non-flood season（October）in 2020（setting of sampling points:upper,middle,and downstream）.The collected samples are processed for high-throughput sequencing.According to the sequencing report:（1）During the period from the flood season to the non-flood season,the aquatic bacterial community may transfer from the water body to the sediment,or the water body changes during the flood season.Conducive to the growth of bacterial communities,sediments are more conducive to the growth of bacterial communities during non-flood seasons.（2）The diversity of plankton communities in sediments during non-flood periods is higher,and the diversity of plankton communities in water bodies during flood periods is higher.（3）The plankton community composition of the section can reflect the water environment of the section to a certain extent.The main dominant species in the water body（bacteria,animals and plants）and five conventional water quality indicators are analyzed by RDA to explore the correlation between the two.The analysis results show that the biological populations that have a greater impact on the flood and non-flood seasons include:Proteobacteria,Bacteroidetes,Verrucomicrobia,Bacillariophyta,Cryptophyta,Chlorophyta,Streptophyta（chain plants）,etc.The physical and chemical indicators of water quality that can be indicated are TP,COD,DO,NH₃-N,and pH.