The Spatial And Temporal Distribution Of Virioplankton And Correlation With Heterotrophic Bacteria In The Bohai Sea

Located between Liaotung peninsula and Jiaodong peninsula, Bohai Sea is asemi-enclosed inland sea formed by the convergence of the Yellow River, the LiaoheRiver and the Haihe River, and it is one of the important areas for marine ecologicalresearch in China. This paper focuses on the investigation of virioplankton andheterotrophic bacteria in the Bohai Sea by flow cytometry, and analyses correlationamong virioplankton, heterotrophic bacteria, picophytoplankton and hydrologicalparameters. In the Bohai Sea, the abundance of virioplankton ranges from6.40×10~5to3.59×10~7ml-1. As to the Liaodong Bay transect, in spring, the west side of the transectwhich is near the Qinhuangdao is more abundant in virioplankton; in summer, thecentral sea area is more abundant in virioplankton; in autumn and winter, both the eastand the west sides of the transect which are near the city of Dalian and the sea area ofQinhuangdao are more abundant in virioplankton. As to the Bohai Bay transect, thecentral sea area is more abundant in virioplankton during all four seasons. As toLaizhou Bay transect, in summer, autumn and winter, the east side of the transectwhich is near the Longkou Port is more abundant in virioplankton. As to the BohaiStrait transect, in spring, autumn and winter, the central sea area is more abundant invirioplankton; in summer, the two sides of the strait are more abundant invirioplankton. In spring, virioplankton abundance shows a significantly higher level inthe Bohai Strait transect; while in the other seasons, virioplankton abundance showsno significant difference among the four transects. Vertically, in summer, there issignificant difference between the virioplankton abundance of the surface and that ofthe bottom of the sea; while in the other seasons, there is no significant difference.The average values of virioplankton abundance are2.98×10~6ml-1,8.28×10~6ml-1,3.38×10~6ml-1and5.77×10~6ml-1in spring, summer, autumn and winter respectively. Apparently, the average value of virioplankton abundance is significantly higher insummer. Diel fluctuation of virioplankton abundance in the anchor station is quiteobvious in summer, while it is not obvious in winter when the trend of diel fluctuationof virioplankton abundance is much the same in the surface and bottom of the sea.In spring, the Bohai Strait transect is most abundant in heterotrophic bacteria,followed by the Liaodong Bay transect, while the Bohai Bay transect is least abundantin heterotrophic bacteria; in autumn, the Bohai Strait transect is most abundant inheterotrophic bacteria; in summer and winter, all the transects show no cleardifference in abundance of heterotrophic bacteria. Vertically, heterotrophic bacteriaabundance has no evident difference in four transects during all the four seasons. Theaverage values of heterotrophic bacteria abundance are7.98×10~5ml-1,3.03×10~6ml-1,8.42×10~5ml-1and8.81×10~5ml-1in spring, summer, autumn and winter respectively.Apparently, the average value of heterotrophic bacteria abundance is significantlyhigher in summer. Diel fluctuation of heterotrophic bacteria abundance in the anchorstation is quite obvious in summer, while in winter, except for22:00, the trend of dielfluctuation of heterotrophic bacteria abundance is much the same in the surface andbottom of the sea.In spring, virioplankton abundance shows significant positive correlation withtemperature and significant negative correlation with salinity; in summer,virioplankton abundance shows significant positive correlation with heterotrophicbacteria abundance, picoeukaryotes abundance, temperature and VBR and significantnegative correlation with the depth of water; in autumn, virioplankton abundanceshows significant positive correlation with Synechococcus abundance, picoeukaryotesabundance and temperature; in winter, virioplankton abundance shows obviouspositive correlation with heterotrophic bacteria.