Seasonal Variation Of Bacterioplankton In The Yellow Sea And Bohai Sea Estuary And Its Influencing Factors

Marine microbes play an important part in marine material circulation,energy flow and ecological regulation of marine ecosystems.The community structure and composition of marine bacteria directly affect the healthy development of the whole marine ecosystem.The bacterial community structure is closely related to the habitat environment of microbes as well as to the variation of seasons.The bacterial community structure not only interacted with microorganisms,but also influenced by changes of environmental factors caused by water mass,human activities,external sea input,seasons,etc.On the basis of above mentioned,we studied the abundance distribution and community structure diversity of virioplankton and bacterioplankton in estuary of the Yellow Sea and the Bohai Sea.The results of this study are helpful to explore the ecological status and evolutionary history of virioplankton and bacterioplankton in the Yellow Sea and the Bohai Sea,to lay a foundation for further analysis of the changes in biome structure,and to provide theoretical basis and data reference for marine environmental assessment.Studying seasonal variation of bacterioplankton abundance in the Yellow Sea and Bohai Sea Estuary and its influencing factors can provide an important theoretical basis for sustainable developments of the ecosystem in the Yellow Sea and the Bohai Sea.This study will focus on the following points:(1)In order to study the distribution characteristics of microbes and the seasonal variation characteristics of community structure diversity,the abundance of virioplankton and bacterioplankton at the estuary of the Yellow Sea and the Bohai Sea was counted by flow cytometry.It was found that the abundance of picoplankton showed significant seasonal differences.The average abundance of virioplankton was August>February>June,and the average abundance of bacterioplankton was June>February>August.The vertical distribution of virioplankton and bacterioplankton is more even than the horizontal distribution which may be related to the exchange of sea water.(2)High-throughput sequencing technology was used to study the seasonal changes in microbial composition and bacterial diversity.The composition of microbial community structure of different seasons was found to be significantly different(P<0.05),and the concentration of ammonium and phosphate played a decisive role.The average abundance of Proteobacteria was about 57.5% in February,46.3% in June,and 47.1% in August;the average abundance of Bacteroidetes was about 35.9% in February,26.4% in June,21.4% in August;the average abundance of Oxyphotobacteria was about 0.4% in February,9.5% in June,14.5% August,and the average abundance of Actinobacteria was about 2.3% in February,7.2% in June,and 7.5% in August.The ?-diversity index shows that the species diversity was June>August>February.The dominant species are Actinobacteria,Proteobacteria,Planctomycetes,Bacteroidetes,Acidobacteria,Firmicutes,Oxyphotobacteria,etc.(3)The microbial composition and key driving factors focused on the estuary of the Yellow Sea and the Bohai Sea were studied.By analyzing the relationship between microbial abundance and environmental factors,it was found that there was a clear correlation between dissolved oxygen of water and the abundance of virioplankton.The virus to bacteria ratio is the most relevant to environmental factors.For the bioinformatics analysis of the microbial community structure diversity in the estuary of the Yellow Sea and the Bohai Sea,influenced by the estuary output and human activity,it was found that the abundance distribution of virioplankton and bacterioplankton affected by estuarine output and temperature changes apparently,while temperature is the main factor affecting the abundance distribution of virioplankton and bacterioplankton.There is a strong correlation between microbial species distribution and concentration of phosphate and nitrate.The abundance of virioplankton and bacterioplankton has a strong correlation with the seasonal trend of the environmental factors.There were significant difference of species composition between seasons(P<0.05),and the species that were significantly different were Bacteroidetes,Oxyphotobacteria,Gemmatimonadetes and Actinobacteria.In addition,through network interaction analysis,it was found that VBR has a significant correlation with the composition of microbial community structure,indicating that the virioplankton may play an important role in controlling the distribution of species of bacterioplankton.