The Study On Microbial Diversity In Mesopelagic Water Of Slope In South China Sea

Ocean,with 71%area on the earth,contains different biological and geochemical activities and plays an important role in global carbon cycle and storage.There is about 91%carbon stored in oceans on the earth,however the most fixed carbon is decomposed in mesopelagic zone during the transfer process to deep dark ocean.This transfer process is influenced by different environmental factors such as oxygen concentration and temperature,water mass and biological activities eapecially the diel vertical migration of swimming mesopelagic fish.The South China Sea,one of the most important ocean areas,contains abundant mesopelagic fish with observation and also plays an important role in global biogeochemical cycle and carbon storage.By investigating the microbial community sturctrue and compositon,since microbe responding quickly to environmental changes around,it is helpful to know energy transportation to deep sea in the South China Sea,mealwhile,the basis for the research for sustainable utilization of marine resources and global climate change.In this study,we collected the samples from the Northern slope in water column of South China Sea in autumn 2014,by quantity PCR technology and Illumina Miseq sequencing associated with clone library based on 16S rRNA gene,mainly analysis the bacterial and archaeal community structure and composition in time-series stations.Generally,bacterial abundance is(1.05±0.01)×10~4 to(1.50±0.02)×10~8 copies/L,archaeal abundance is(2.11±0.01)×10~3 to(2.05±0.01)×10~6 copies/L.Obviously,bacteria took one to two orders of magnitude higher than archaea.Both archaeal and bacterial abundance in surface water(<200 m depth)took one to two orders of magnitude higher than mesopelagic water(>200 m depth),and the most abundant layer is 65 m depth.There were eight common bacterial groups found in water colulmn of South China Sea,among them over 50%are Proteobacteria and Bacteroidetes.Eapecially in time-series stations,SAR11 and SAR406 clades are most abundant in proteobacteria.What's more,Flavobacteriaceae was abundant and uniformly distributed in almost every station and layers.Different patterns in different station and depth,with some bacterial species such as Alcanivoraceae outbreak in 450 m depth,which may related to biological activities of mesopelagic fish.According to the canonical correlation analysis(CCA),depth was thought to be the predominant environmental factors for bacterial distribution.For archaea,the dominate groups are Thaumarchaeota(Marine Group I)and Euyarchaeota(Marine Group II and Marine Group III).The former one is in high abundance than Euyarchaeota in deep water which belongs to ammonia-oxidizing archaea.Dissolved ocygen concentration was thought to be the key factor affecting archaeal distribution,but we still need to be study the corelation between archaeal distribution and environmental factors.About Marine Group II and Marine Group III,are both belong to Thermoplasmata which is a class of the Euyarchaeota.For lacking of pure culuture,the two archaeal groups are researched less.All the data could provide basic reference for microbial seasonal variation and functional genes in subsequent research.