| As a typical representative of marine picocyanobacteria,Synechococcus is widely distributed in marine environment,and its ecological distribution and temporal and spatial variation are strongly influenced by environmental factors.Cyanophage are an important component of marine viruses,which regulate the abundance and community structure of cyanobacteria.The ecological characteristics of cyanphages are influenced by both environmental factors and host cyanobacteria community,Aoshan Bay is a typical coastal eutrophic environment in temperate zone,and its environmental conditions have a great temporal heterogeneity.In this thesis,we conducted a one-year time series study on the community structure of Synechococcus and its intracellular T4-like and T7-like phages in Aoshan Bay to explore the variations and co-variations of the community of Synechococcus and its phages in temperate coastal environment.The main results of this thesis are:1.The abundance and diversity of Synechococcus in Aoshan Bay were higher in summer and autumn,but lower in spring and winter.The Synechococcus community are disticnt in time-series of the whole year.The samples that were close in time distnace had higher community similarity.A total of 19 clades were identified,and Clade Ⅰ,Ⅱ,Ⅳ and Ⅸ were the dominant clades of subcluster 5.1.Subcluster 5.2 were abundant in summer and autumn,and CB5 was the dominant clade.Most of the Synechococcus clades are positively correlated.Environmental factors such as temperature,salinity and nutrients influence the time series variation of the Synechococcus community.The correlation between dominant OTUs and environmental factors is higher than that between clades and environmental factors..2.Few differences were observed in the time series variation of intracellular T4-like cyaophage community.The samples that were close in time distnace had higher community similarity.A total of 16 clades were identified,including two clades unique to Aoshan Bay.The dominant clades appeared alternately in the time series,and the covariation among the clades is weak.The time series variations of community composition were small at the clade level,but varied greatly at the OTU level.Moreover,the correlation between dominant OTUs and environmental factors is more significant than that between clades and environmental factors.3.The temporal variation of the intracellular T7-like cyaophage community is more remarkable than that of T4-like cyaophage.A total of 9 clades of intracellular T7-like cyaophages have been identified in Aoshan Bay,with one of which unique to Aoshan Bay.The temporal variation of T7-like cyaophagces are distinct in both clade and OTU levels,but showed no correlation with the environmental factors.4.There was a close relationship between Synechococcus and intracellular cyanophage communities in Aoshan Bay.The T4-Iike and T7-like phages of Synechococcus showed positive and negative correlation with the Synechococcus clades.respectively.The cyanophages may directly or indirectly regulate the temporal variation of the Synechococcus community.In this study,the ecological characteristics and environmental adaptation mechanism of Synechococcus and its phages community in Aoshan Bay were investigated in terms of time series.There were obvious seasonal differences and close relationships in the time series of the community structure of Synechococcus and its viruses in Aoshan Bay.Environmental factors such as temperature,salinity and nutrient salts were important factors affecting the ecological distribution and community structure of Synechococcus in the coastal environment.Synechococcus and Synechococcus phages community were closely related in time series.The community structure of Synechococcus phages was affected by environmental factors and the community structure of Synechococcus. |
