Diversity Analysis Of Microbial Community In The Bohai Sea

As the cornerstone of the ecosystem,the microbial community supports the entire biosphere and also plays an irreplaceable role in the biogeochemical cycle.The Bohai Sea with an average depth of 18 meters is one of the four marginal seas in China.It is deeply affected by increasing human activities.In recent years,summertime hypoxia in the bottom seawater of the Bohai Sea has been continuously reported.Hypoxia will increase environmental stress on the total microbial community,leading to changes in the microbial metabolism,distribution,and biogeochemical process.Marine microorganisms affect the dynamic balance of carbon dioxide between the ocean and the atmosphere through the remineralization of organic matter,and thereby affect the global climate.The high primary production and the shallow water depth of the Bohai Sea bring a large amount of biogenic organic matter and reduce their turnover time.which causes a large amount of organic matter to settle on the seafloor before decomposition.Therefore,a large number of microorganism-mediated biological processes remain in the sediment instead of seawater.That makes the study of the microbial communities in both seawater and sediments equally important in the Bohai SeaBased on the hypothesis that the decrease of oxygen concentration in the Bohai Sea will change the microbial communities,our research focused on the differences of both particle-attached and free-living bacterial communities from different dissolved oxygen concentrations in seawater.Our research indicates that oxygen concentration does change the composition of the microbial community,but the impact is limited.Ammonium it the most important biogeochemical factor that influences the bacterial communities.The particle-attached communities and the free-living communities have different responses to the change of environmental factors.Microbes form particle-attached communities has a closer interaction.We investigated the distribution of bacterial communities and archaea communities in three shallow sediment cores of different regions in the Bohai Sea,assessed the influence of different environmental factors on microbial communities,and explored their assembly mechanisms.The composition of the bacterial communities does not change much with depth,while the archaeal community is quite the opposite.The increase of depth reduces the biodiversity of the bacterial communities,while the biodiversity of the archaeal communities first increases and then decreases with the depth.Environmental selection significantly affects the microbial communities,and the most important factors are those parameters related to dissolved inorganic phosphorus and dissolved inorganic nitrogen.Both the bacterial communities and the archaeal communities conform to the distance-decay pattern on the vertical distance,and the archaeal decay rate is higher.The interaction between bacteria and archaea is strong with different modules of their own characteristics.The main assembly mechanism of bacterial communities is homogeneous selection,while the development of archaeal communities is dominated by stochastic processes.Our research shows that the microbial communities in the Bohai Sea have a complex dynamic pattern,and the current microbial community is formed under the combined effect of a large number of factors.