Analysis Of Virioplankton Abundance And Correlation With Picoplankton And Heterotrophic Bacteria In The Northern Yellow Sea

In this paper, the Northern Yellow Sea samples were collected during the Orient Red cruise in Agust 2006(summer) and Feburary 2007(winter).Virioplankton, picoplankton and heterotrophic bacteria in the Northern Yellow sea are determined by flow cytometry, and analyze the correlation between virioplankton and picoplankton, heterotrophic bacteria, and environmental parameters as well.There are few reports on marine bioecology in the Northern Yellow Sea, except phytoplankton. The purpose of this study is to provide more numerical dates and information for the study of bioecology in the Northern Yellow Sea, and to understand population structure and dynamics of biology in the Northern Yellow Sea further.We identified two different types of virioplankton (V-I virioplankton and V-II virioplankton) in the Northern Yellow Sea.Viral abundance ranged from 6.83×105 to 6.94×106 particles mL-1(3.17×106 mL-1on average) in summer, and from 2.76×105 to 4.00×106 particles mL-1(1.23×106 mL-1 on average) in winter. In horizontal distribution, the area of the high viral abundance exists around boundary of the Bo Sea and the Yellow Sea in summer, and so is the area between ShanDong peninsula and LiaoDong peninsula in winter.In vertical distribution, virioplankton abundances at 30m and bottom water samples are lower than that of 10m water samples in summer because of the North Huanghai Sea Cold Water Mass; There are no distinct variation in each water layer in winter(P﹥0.05). Virioplankton abundance in summer are obviously higher than that in winter(P﹤0.01).Daily variations of virioplankton abundance in each layer in summer and winter in the NorthernYellow Sea are almost consistant: virus abundance reachs to the maximum at 10:00 and 19:00 at 10m, 30m and bottom layer, the low abundance appears at 16:00 and 22:00. There is the obvious variance between the two values in 24 hours(P﹤0.01), which indicated that the variance of viral abundance is caused by the time of collected samples and the consistence on the time of collected samples must be considered in practical research to analyze the distribution of biology abandunce.Two picoplankons (Synechococcus and Eukaryote) were detected in terms of their scatter light and fluorescence characteristics of photosynthetic pigments, but Prochlorococcus is not found in all samples in summer and winter. During summer of 2006, the average values of Syn, Euk abundance are 3.16×104cells mL-1, 1.42×103 cells mL-1, respectively; During winter of 2007, the average values are 4.31×103 cells mL-1, 2.34×103 cells mL-1, respectively. In horizontal distribution, the high Syn abundance (×105cells mL-1) exists around boundary of the Bo Sea and the Yellow Sea in surface water column, the low Syn abundance(×103cells mL-1) exists in the area of Cold Water Mass at 30m and bottom layer in summer; Syn and Euk abundance in the eastern of 123°E is higher than that in the western of 123°E in winter(P﹤0.01). In vertical distribution, Syn and Euk abundances at 30m and bottom water samples are lower than that of 10m and surface water samples in summer. Syn abundance in summer are obviously higher than that in winter(P﹤0.01), but Euk abundance in summer are lower than that in winter(P﹤0.01).Besides, three types of bacteria (B-I bacteria, B-II bacteria and B-III bacteria) is identified. The average values of heterotrophic bacteria abundance in summer and winter are 2.60×105 cells mL-1, 2.40×105 cells mL-1, respectively. The tendency of heterotrophic bacteria abundance in horizontal distribution is almost coincident in summer and winter, and so is the area of high abundance. Bacteria abundance at 30m and bottom water samples are lower than that of 10m water samples(P﹤0.01) in summer. Heterotrophic bacteria abundance has no obvious variation in summer and winter (P﹥0.05). The minimum values of bacteria abundance appear at 16:00 in each layer in summer and winter.In summer, Viriplankton is positively correlated with heterotrophic bacteria abundance; In winter, virioplankton abundance is positively correlated with Syn abundance.also with Virus-to-Bacterium Ratio (VBR). In winter, virioplankton abundance is positively correlated with Syn abundance and also with VBR. These correlation shows that phages is dominant in summer while phytophages is major in winter..The daily variation consistency exists in virioplankton and bacteria abundance in surface, 10m and bottom water layer in summer, which demonstrate further that the positive correlation exists between virioplanton and bacteria abundance in summer; The variation consistency does not exist between virioplanton and heterotrophic bacteria abundance in winter.when temperature exceeds 20℃in summer, virioplankton abundance is negatively correlated with temperature. Meanwhile, the negative correlation between virioplankton abundance and salinity emerges in summer in the Northern Yellow Sea. The hypothese that viral integrity is altered because of salinity may explain this negative relation. Since salinity in water columns is entirely driven by mixing processes, no correlation between virioplankton abundance and salinity exists during the winter season.