Microbial Community Structure Of Eutrophic Urban Lake And Influence Factors

Nanhai Lake,located in the hinterland of Mengxin Plateau,is the largest and most important lake ecosystem in Baotou,Inner Mongolia.These years,due to the increasing disturbance of anthropogenic activities,it has led to great changes in the ecological environment of Nanhai Lake.Its water quality has been greatly improved after years of governance,but the pollution problem has not been fundamentally solved.As an important part of the ecosystem,microorganisms play a vital role in the material and energy cycle of the ecosystem,while the ecosystem also has different degrees of influence on the microbial community.Therefore,the study on the microbial community structure of Nanhai Lake and the assessment of the water ecological condition of Nanhai Lake are of reference significance for the environmental management and pollutant prevention and control of eutrophic urban lakes in the Mengxin Plateau represented by Nanhai Lake.In this study,Nanhai Lake was divided into different functional zones according to its functional division and topography,and the water quality and sediment parameters of Nanhai Lake were analyzed to explore their changes with seasons.The microbial diversity of the water and sediment was measured by using high-throughput sequencing technology,and Study of microbial community diversity.The main research findings are as follows:The physical and chemical indicators of the water varied more significantly with the seasons,with most indicators showing the highest values in winter and the lowest values in summer,but the p H exceeded the standard range of natural water(6-9)in summer.The variation patterns of temperature and p H and dissolved oxygen were basically the same,and the variation patterns of total nitrogen,ammonia nitrogen and nitrite nitrogen were basically the same,while total nitrogen and total phosphorus concentrations exceeded the surface water V level in some periods.In contrast,the physicochemical indicators in the sediment did not change significantly in the short term and varied less in each season,and the phenomenon was caused by the aggregation of pollutants in the water column.The analysis of diversity indices revealed that the structural diversity of microbial communities showed different changes with the seasons: the abundance of microorganisms in the water column decreased significantly in winter and summer,with ACE and Chao1 indices lower than 468 and 498,respectively.the diversity was richer in autumn,with ACE and Chao1 indices higher than 1270 and 1255,respectively.while the diversity of microorganisms in spring was between winter and summer and autumn.The diversity of sediment microbial community structure was higher in spring and autumn,with ACE and Chao1 indices higher than 1168 and 1160,respectively,followed by summer and the lowest in winter,with ACE and Chao1 indices lower than 499 and 1015,respectively.microbial community structure in water bodies and sediments changed somewhat with the seasons,thus suggesting that seasonal changes may be the main factor causing changes in microbial community structure in the lake.The microbial community structure in the water column and sediment changed with the seasons,thus indicating that seasonal changes may be the main factor causing changes in microbial community structure in the lake.The results of microbial community analysis showed that the composition of the community structure changed with seasonal changes,and the microbial composition of the water body at the phylum level mainly had Bacteroidetes,Planctomycetes,Actinobacteria,Verrucomicrobia,Chloroflexi and Cyanobacteria are the main taxa.At the genus level,there are mainly CL500-3,norank＿f＿LD29,hgc I＿clade,Unclassified＿c＿Cyanobacteria,Mycobacterium as genera with higher abundance in different seasons.In contrast,the microbial community composition in the sediment was more stable,with Proteobacteria and Chloroflexi being the most abundant phylum in different seasons in each region at the phylum level.At the genus level,Thiobacillus and norank＿f＿Anaerolineaceae were more abundant in all seasons.As the formation and melting of ice caps during the four seasons affect the water environment,the external conditions of the lake change,and the change of the water environment leads to the change of the sediment and the change of the microbial community structure in the water and the sediment,so the influence of each environmental factor on the microorganisms varies slightly in different seasons and different regions.In general,TN,p H,TP and dissolved oxygen in the water column are the environmental factors that have a greater impact on the microbial community structure in the water column,and TN,p H,TP and TOC in the sediment are the environmental factors that have a greater impact on the microbial community structure in the sediment.The results of microbial functional gene prediction in Nanhai Lake showed that it was mainly reflected in the differences between water and sediment,in the KEEP functional diversity of microorganisms in water: spring > autumn,winter and summer,and in sediment: summer > autumn,winter and spring.In the secondary functional layer analysis,the microbial functions in the sediment in the top ten sub-functions compared to the water column changed,specifically in the relative abundance of exogenous biodegradation and metabolism and nucleotide metabolism,which accounted for a higher percentage in the water column and a higher percentage in the sediment.