Changes Of Bacterial Community Structure In Urban Lakes During Ice Period In Cold And Arid Regions

Nanhai Lake is a typical small urban lake.It plays an important role in climate regulation,conservation of water resources,and beautification of city.Because it is located in the high latitudes of the cold and arid regions,the seasonal ice period makes it special.In order to reveal the relationship between bacterial community structure and environmental factors during the ice period of Nanhai lake,and provide a scientific basis for eutrophication and ecological protection,the Nanhai lake was divided into four areas with reference to the topography and landscape in this study.Three representative sampling points were set up in each area,and the samples were collected in November 2017,January 2018 and April 2018.The high-throughput sequencing technology was used to detect the bacterial community structure,and the physical and chemical indicators of each sampling point were analyzed.Through the analysis of bacterial community,the bacterial community structure characteristics of Nanhai lake during the ice period were identified.Correlation analysis was used to determine the environmental factors affecting the bacterial community structure.The main research results were as follows:From the perspective of time,the environmental factors of water changed significantly with time.Compared with the non-ice period,the water pollution during ice period was more serious.The indicators of environmental factors in the sediments were affected by changes of water environment factors for a long time,and there was no significant changes in a short time.From the perspective of space,the nutrition level of each lake area could be roughly classified into tourist development area>aquatic vegetation area>water inlet area>lake center area.Sample species abundance and uniformity were inversely related to nutrient levels.Bacterial?diversity was affected by various factors such as hydration of the Yellow River,condensation of ice bodies,plant growth and corruption,and the similarity of bacterial community structure in different areas during icing was different.According to the phylum,the dominants were Actinobacteria?23.9%?,Cyanobacteri a?19.6%?,Proteobacteria?17.1%?,Bacteroidetes?10.5%?and Chloroflexi?8.3%?,etc.Ac cording to the genus,the dominants were hgcI-clade?17.3%?,unclassified-c-Cyanobacteri a?14.6%?,unclassified-p-Chloroflexi?13.8%?,and thiobacillus?10.1%?,etc.Due to the large changes in external conditions during the icing process and the dissolution process of ice bodies,the environmental factors affecting planktonic bacteria were different in different periods.In general,TN,DO and pH in water were the main factors affecting the bacterial community in ice period.The relatively stable living environment in the sediment made the environmental factors affecting the bacterial community structure relatively stable,and did not differ with the freezing and dissolution processes.In general,TN,NH₃-N,and C/N had a greater impact on the bacterial community structure of sediments.Controlling these environmental factors is an important measure to improve the water quality of Nanhai lake during ice period.