Temporal And Spatial Succession Characteristics Of Microflora And Influence Of Environmental Factors In Jinpen Reservoir

The natural material cycle cannot be separated from bacteria.The population structure and metabolic activity of microorganisms affect the process of material cycle,and the changes of environmental factors will lead to changes in the population structure and metabolic activity of microorganisms.Therefore,the study of the spatial and temporal distribution characteristics of bacterial population structure and the relationship between microbial metabolic activity and environmental factors is of great significance to master the water quality and water environment protection of Jinpen Reservoir.In this study,Xi ’an Jinpen Reservoir was selected as the research object from July 2021 to July 2022 to conduct in-situ tracking and monitoring of the water environment of the reservoir.Meanwhile,high-throughput sequencing technology and Biolog microplate technology were used to explore the diversity,population structure,metabolic activity and response to water environmental factors of bacteria,microorganisms and surface sediments in different periods.The dynamic network relationships among bacterial communities were analyzed.According to the mixing state and external influence of the reservoir,the study is divided into four stages,which are natural mixing period,flood season,forced mixing period and stratification period.The main results of this study are as follows:(1)Water quality have obvious temporal and spatial variation characteristics.The water quality was better in the natural mixing period,but deteriorated for a short time due to the inflow of rainstorm runoff,and recovered gradually after the runoff.Under anaerobic conditions at the bottom of stratification period,the bottom sediment pollutants release and the water quality deteriorates.During the artificial forced mixing period,dissolved oxygen content in water increased and pollutants were reduced.(2)The process of bacterial population structure succession in Jinpen Reservoir,Actinobacteriota and Proteobacteria were dominant groups of bacteria in all four periods,and had their own unique dominant groups in each period.In the natural stratification stage,Cyanobacteria and Bacteroidota were the dominant bacteria.In flood season,Firmicutes and Bacteroidota were the dominant phyla.Bacteroidota was the dominant phylum in the natural mixing stage.The dominant bacterial genera in water were CL500-29＿marine＿group,hgc I＿clade and Arthrobacter of Actinomyces,Cyanobium＿PCC-6307 of Cyanobacteria,and Methylobacter of Proteobacteria.The bacterial community richness increased during flood season and aeration system operation.(3)The bacterial Alpha diversity index in Jinpen Reservoir was significantly correlated with water temperature,dissolved oxygen,total nitrogen and total phosphorus.Total phosphorus,water temperature,total nitrogen and iron are the main environmental factors affecting microbial population structure.There is a large gap between the samples of different periods in the stratification period,and a variety of environmental factors can affect its structure.The species structure was mainly affected by water temperature and dissolved oxygen during flood season.Water temperature,total nitrogen,manganese and dissolved organic carbon greatly affected the artificial forced mixing period.In the early stage of natural mixing,water temperature,total nitrogen and total phosphorus were the main factors,while in the late stage,iron was the main factor.Through symbiotic network analysis,the microbial interaction in natural mixing stage was stronger than that in natural stratification stage.(4)The microbial metabolic activity was different in different periods,and the utilization degree of organic carbon sources was different.The microbial utilization ability of organic carbon sources was stronger in flood season and forced mixing period,and the utilization of esters was the best.The utilization of organic carbon sources in stratification and natural stratification periods is unbalanced,and the utilization of alcohols,amines and acids is reduced.The utilization of organic carbon sources by microorganisms in flood season and forced mixing period was more balanced.The metabolic capacity of microbial organic carbon source is regulated by environmental factors,especially water temperature and dissolved oxygen.(5)The dominant bacteria were Proteobactria,Actinobacteria,Firmicutes and Verrucomicrobia insurface sediments.There are complex symbiotic and antagonistic interactions among these bacteria.The metabolic activity of bacteria in surface sediments was different at different periods,and the utilization of esters was the best.Redundancy analysis showed that the contents of total nitrogen,total phosphorus and total organic carbon had different effects on bacterial population structure and metabolic activity in surface sediments.