The Response Of Microbial In Sediment And Water Of Poyang Lake To The Inputs Of N?P And Heavy Metals Pollutions In Raohe River

Freshwater lakes play an important role in the terrestrial water system.They have extremely important ecological and social values in regulating the floods,ensuring drinking water safety and carrying out freshwater aquaculture.Along with social economy development,the eutrophication and heavy metal pollution are becoming more and more severe,therefore,great attention has been paid to the eutrophication and heavy metal pollution.It is difficult to summarize and compare the existing research findings and draw a perfect conclusion because of persistence of nitrogen and phosphorus input and heavy metal pollution processes and spatial differences between different lakes.Great attention has been paid to the nitrogen and phosphorus loading or heavy metal pollution in most existing researches,but little attention has been paid on the integrated pollution caused by the two.In this study,Raohe Rivers estuary is selected as the study site.The water and sediments in the estuary were taken as the research objects and six sampling points of Site1~Site6 were set up and divided.It is divided into three areas: riverway(R),confluent area(RL),and lake(L).Surface water,overlying water and sediment samples are collected one after another.the nutrients,heavy metals and microbiota in the sample should be determined and the characters of space-time change between the two should be analyzed,which can explain the responding mechanism of microbiota to the input of nutrients and heavy metals,provides a reference for objectively appraise of the pollution situation of Poyang Lake and provide theoretical basis for ecological safety and scientific management of the lake.The results are as follows:(1)The distribution of nutrients and heavy metals in the estuary was most affected by seasonal change,followed by the different vertical areas,and the least affected by the sample area.Most of the nutrients and heavy metals in different hydrological periods have different distribution characteristics in the process of rivers entering lake: The dry season showed a unimodal distribution,the water-falling stage showed an upward trend,and the overflowing period showed a U-shaped distribution.The distribution of nutrients and heavy metals in the vertical direction is mainly affected by the sedimentation-resuspension dynamic process,and with sedimentation as its main movement mode.The frequency of nutrient and heavy metal exchange at the surface water and overlying water interface is lower than that of the overlying water and sediment.(2)microbiota is mainly affected by different hydrological periods and different vertical directions,the effect of the vertical direction is greater,while the community difference is least in different sample area.The difference microbiota between the sample plots is mainly reflected between the river and the lake.In the different hydrological periods,the microbiota structure of the water-falling stage and the overflowing period are closer,and the most diverse microbes are enriched during the overflowing period.In different vertical areas,the microbiota structure of the surface water and the overlying water is closer,and the sediments are enriched with the most diverse microbes.the order of the relative abundance of the microbial community in the Raohe River estuary from high to low is Proteobacteria,Bacteroidetes,Actinobacteria,Cyanobacteria,Acidobacteria,Chloroflexi,Planctomycetes,Gemmatimonadetes,Nitrospirae.Based on the PICRUSt function prediction,the main functional metabolism of microorganisms includes Carbohydrate metabolism,Energy metabolism,Lipid metabolism,Nucleotide metabolism,Amino acid metabolism.Microbiota composition is significantly different in different hydrological periods,but there is no significant difference in microbial function,which reflect the characteristic of functional redundancy with microbial communities.Microorganisms in the vertical direction have similar functional types,but different metabolic priorities in different locations reflect the preference of microbial community functions in different environments.(3)Nutrients and heavy metals mainly affect the water microbial community.The correlation between nutrients and heavy metals and the microorganisms gradually increased in the dry season,water-falling stage and the overflowing period.The correlation between nutrients and heavy metals and the microorganisms decreased gradually in upper layer water,overlying water and sediment.Nutrients that have significant effects on water microbiota include TN,DTN,NH4-N,NO3-N,TP,DTP,AP,TOC;heavy metals include Cd,Pb,Cu,and environmental parameters pH,EC,Temp,DO,NTU also has a significant impact.Nutrients and heavy metals that have significant effects on sediment microbiota include Zn,TOC,NO3-N,NH4-N,Cd,and AFDM.In addition,water content also significantly affects the microbial community composition of sediments.There is little effects of nutrient salt and heavy metal input on microbial function,and reflected in the change of community structure clearly,which is manifested by directly affecting some non-high abundance microbial groups,thereby changing the overall microbes indirectly.(4)A number of microbial species that show positive changes in nutrients,heavy metals,and environmental parameters are identified in this study.Among them,Cyanobacteria responded most positively to environmental changes,and were also affected by changes in nitrogen and phosphorus nutrients,heavy metals and environmental parameters.Actinobacteria respond to changes in nitrogen,phosphorus nutrients and heavy metals at the same time.Latescibacteria,Nitrospinae,Bacteroidetes and Acidobacteria can greatly reflect the changes of nitrogen and phosphorus nutrients in the environment.The Chloroflexi and Nitrospirae mainly reflect the response of microbiota to changes in heavy metals in the environment.