Relationship Between Algal Community Structure And Functional Microbial Communities In Drinking Water Reservoirs

With the gradual aggravation of groundwater pollution and the strict restriction on the exploitation of urban groundwater,reservoirs have become the main water supply source in cities.However,the poor fluidity of reservoir water and obvious seasonal thermal stratification result in anaerobic sediments at the bottom of reservoir,and algae overgrowth seriously affects the safety of water supply.Therefore,exploring the relationship between algae outbreak and microbial communities in drinking water reservoirs has become a new scientific proposition.In this paper,the drinking water reservoirs in Xi'an was taken as the research object,and the coupling mechanism between algal community structure and functional microbial communities was revealed by combining microbial communities metabolic profiles and high-throughput DNA sequencing technology,in order to provide scientific basis for improving water quality of drinking water reservoirs.The conclusions are as following:(1)During the outbreak of Microcystis in Lijiahe reservoir,with the increase of water depth,the algal cell concentration decreased gradually(3364.33±234.59?821.67±273.32 10~4 cells/L),the algal community structure changed dramatically,and the metabolic activity(AWCD)and relative abundance of bacterial community increased gradually.In vertical aquifer,the relative abundance of Chlorobi and Planctomycetes increased significantly with the decrease of algal cell concentration.PCA showed that bacterial community in surface water was closely related to temperature,dissolved oxygen,pH,ammonia nitrogen and algal cell concentration.Total organic carbon had a siginificant effect on bacterial community at 3 m depth.The bacterial community at 6 m depth are mainly controlled by total nitrogen,nitrate nitrogen and conductivity.(2)In summer and autumn,Microcystis and Aphanizomenon erupted successively in Lijiahe reservoir.The diversity of algal communities increased from late autumn to winter,and Bacillariophyta(60.74%?72.13%)was the dominant algae in spring.RDA showed that Microcystis,Staurastrum and Melosira were positively correlated with pH,temperature,Fe and Mn.Aphanizomenon and Chlorella Pyrenoidosa were positively correlated with total nitrogen,ammonia nitrogen and turbidity.Synedra,Scenedesmus,Oocystis,Pandorina and Pinnularia are closely related to total phosphorus,dissolved oxygen,nitrate nitrogen and dissolved organic carbon.(3)The water quality of Jinpen reservoir is good.Bacillariophyta and Chlorophyta are the dominant algae species in Jinpen reservoir.Cyclotella(91.39%?96.70%)dominated in spring and summer,and diversity of algal communities increased significantly in autumn.RDA showed that the conductivity,pH and total phosphorus were positively correlated with Synedra,Pediastrum,Cyclotella,Cymbella.And dissolved oxygen,temperature,conductivity,pH,and Fe are the main water quality factors affecting the succession of algal communities.(4)DNA sequencing technique was used to diagnose the accompanied bacterial community during Microcystis-induced phrase.The results showed that the metabolic activity and communities diversity of bacteria and fungi increased with the increase of algal cell concentration(576.33±113.00?4022.81±298.55 10~4 cells/L)in surface water.During the outbreak of Microcystis,the accompanied bacterial communities were Proteobacteria(31.29%),Actinobacteria(20.98%),Firmicutes(13.21%)and Bacteroidetes(6.92%);and fungi were Chytridiomycota(29.07%).RDA showed that the accompanied bacterial community were closely related to temperature,dissolved oxygen,pH,total nitrogen,nitrate nitrogen,ammonia nitrogen and conductivity during algal outbreak,while the accompanied fungal community were closely related to water quality factors such as chlorophyll a,total phosphorus,dissolved organic carbon,algal cell concentration,Fe and Mn.(5)Static reactor simulate the decline period of Microcystis,and results showed that pH(8.11±0.02?7.85±0.02),chlorophyll a(56.90±4.25?1.31±0.35?g/L),total nitrogen(4.62±0.04?3.44±0.06 mg/L),ammonia nitrogen(1.86±0.01?0.01±0.00mg/L)and total phosphorus(0.11±0.01?0.03±0.01 mg/L)decreased gradually,while nitrate nitrogen(2.87±0.00?3.79±0.16 mg/L)increased gradually.The fluorescent soluble organic matter is fulvic acid-like,humic acid-like and tryptophan-like.Richness diversity and Shannon diversity showed that the diversity of bacterial community decreased with the decline of algae.During the decline of Microcystis,the relative abundance of Exiguobacterium sp.,Rhodobacter sp.,Legionella sp.and Planctomyces sp.increased significantly.Network analysis showed that most bacteria were closely related to nitrate and dissolved oxygen.RDA showed that chlorophyll a,nitrate nitrogen,dissolved oxygen,dissolved organic carbon and pH were closely related to the change of bacterial community structure.