Community Structure And In-situ Regulation Of Functional Microorganisms In Stratified Reservoirs

Drinking water reservoirs are different from natural lakes.They are generally large-scale deep-water facilities constructed artificially for the main purpose of water storage and water supply.Its water quality is of great significance to the lives of residents in large and medium-sized cities.A comprehensive and in-depth study of the coupling mechanism of"hydrological and hydraulic characteristics-water pollutant distribution characteristics-dynamic distribution of functional microbial communities"in microecosystem of drinking water reservoir is of great significance for understanding the stability of the water source reservoir ecosystem and the safety management of reservoir water supply.In this study,we taken Jinpen Reservoir and Lijiahe Reservoir as the research obiects to study the temporal and spatial change characteristics of water quality parameters of two drinking water reservoirs during the natural mixing period;focu on the regulation of the reservoir water body by the operation of the artificial regulation device—Water-lifting aerator device;analyze the regulation mechanism of the artificial regulation effects on the functional microbial communities in stratified drinking water reservoir;and explore the association mechanism between water environmental factors and functional microbial community structure and composition,provides a scientific basis for studying the water quality and safety of drinking water reservoirs.The findings include:(1)The results showed that water temperature decreased monthly during the natural mixing period in Jinpen Reservoir.The concentrations of ammonia nitrogen,total phosphorus,and manganese were at a relatively low level;the concentration of total nitrogen was relatively constant,maintained at 1.01?1.19 mg/L,consistent with the change trend of nitrate nitrogen;DO concentration was at a high level with little vertical fluctuations.(2)During the natural mixing period in Lijiahe Reservoir,water temperature decreases with time,and the vertical temperature differences was small;DO concentration was high,fluctuating between 7.91 to 9.87 mg/L.The contents of ammonia nitrogen,total phosphorus and iron fluctuated greatly;the concentrations of total nitrogen and nitrate nitrogen were relatively constant.The highest concentration of DOC(dissolved organic carbon)reached to 5.2 mg/L,and it decreased monthly from November to January.The number of nitrogen-fixing bacteria colonies gradually increased with the depth of water.The difference was the largest in November,with1.07×10⁴ CFU/mL in the surface layer and 2.23×10⁴ CFU/mL in the bottom layer.(3)Through high-throughput sequencing technology,network and SEM(structural equation modeling)methods,the response characteristics of AAPB(aerobic anoxygenic photosynthesis bacteria)community in Jinpen Reservoir to artificial regulation was studied.The results showed that there were significant differences in AAPB community structure and composition during the artificial regulation in Jinpen Reservoir,and there were a large number of unclassified species to be discovered and identified.At the phylum level,Proteobacteria was the most dominant,and the relative abundance accounted for 90%or more.The dominant species mainly included Limnohabitans,Hydrogenophaga,Bradyrhizobium,Methylobacterium at the genus level.In different periods of artificial regulation,the dominant bacteria and their abundance changed significantly.The interaction between AAPB species had complex changes.During the study period,keyspecies such as Phycicoccus and Methyloversatilis in AAPB community maintained a significant positive correlation with other species.Among the environmental factors,such as DOC,ORP,and NO₃^--N had a significant impact on keyspecies,thereby affecting the structure and composition of the entire AAPB community.SEM results showed that the std.coefficient of DO on AAPB community structure was 0.87,which significantly affected the succession of the AAPB community during the artificial regulation period.(4)The operating of artificial regulation device in Lijiahe Reservoir effectively improved the seasonal thermal stratification.The results of high-throughput sequencing showed that the relative abundance of Cyanobacteria and Proteobacteria were the highest;and a total of 290 genera were identified at the genus level,among which Pseudanabaena was the most dominant genus.The community structure of nitrogen-fixing bacteria differed significantly in different periods,with the largest difference in the middle and late stages of operation.Network analysis results showed that the nitrogen-fixing bacterial communities were mainly positively correlated,and the keyspecies were closely related,which had significant effects on the overall development of the nitrogen-fixing bacterial community.SEM results showed that DO was the main factor regulating the changes of nitrogen-fixing bacterial communities(std.coefficient=0.72);under the combined action of T and DO,the physical and chemical parameters had a significant negative impact on the nitrogen-fixing bacterial community(5)A total of 9 phyla and 400 genera of fungal communities were identified during the artificial regulation period in Lijiahe Reservoir.The fungal community structure and its diversity vary greatly.Chytridomycota and Ascomycota were the most dominant species in all water bodies.At the genus level,Biappendiculispora was the most abundant species,with a maximum of 80%.Network analysis showed that the relationship between fungal communities differed significantly during the period of artificial regulation.With the operation of the artificial regualtion device,the number of species nodes in network gradually increased,and the relationship between bacteria species gradually becomed closer.In the later-stage of operation,a large number of rare bacterial species played an important role in the fungal community and affected the overall survival and development of the community.SEM results showed that T and DO jointly controlled the temporal and spatial changes of fungal community structure during the artificial regulation(std.coefficient=-0.62);at the same time,under the influence of T and DO,nutrients significantly affected the fungal community structure and composition(std.coefficient=-0.73).(6)A total of 52 phyla 864 genera were identified in the sediments of Jinpen Reservoir during the operation of the Water-lifting aeration device.There were significant differences in dominant species and their diversity.At the phylum level,Proteobacteria was the most dominant bacterial species during the study period(26.37%?42.53%),followed by Bacteroidetes(13.35%?24.45%).Network analysis showed that the relationships between dominant bacterial communities were increased and then decreased.It is speculated that the bacterial communities were dominated by negative correlations such as predation and competition;the relationships between rare species were gradually getting closer,and it is speculated that the relationships were mainly based on primitive cooperation,mutual benefit and symbiosis.SEM showed that the bacterial community was mainly affected by T and DO(std.coefficient=0.39),and sediment enzyme activity was significantly regulated by nutrients(std.coefficient=0.70).