Distribution Of Virioplankton In Response To Environmental Variation In North China

Oceans of the earth occupy 13.7×109 km3, covering 71%. As the largest ecosystem on the earth, oceans provide the largest habitat and good nutrition conditions for a variety of organisms. It’s complex and changing environment, ecological environment of special area such as high salinity and pressure, low temperature and nutrition, and absence of light, result the diversity of species, the genetic composition and ecological functions. The special environment has great significance to human beings for further study of marine organism and protection of marine ecosystem.Viruses are one component of the environment which exist almost all ecosystems in the world-from deep sea sediments to the atmosphere. Ocean virioplankton play an very important role in cycling of substance and flow of energy, and the survival and development of other species in the marine environment. Therefore,in recent years, the study of marine virioplankton becomes a hot topic of marine ecological research. To understand temporal and spatial distribution of virioplankton in response to environmental changes in north China Sea, four season samples were collected from 4 cruises during June,2011 and November,2012 in the north Yellow Sea (NYS), south Yellow Sea (SYS) and Bohai Sea (BS).Distribution of surface virioplankton in four seasons identical to Yellow Sea Warm and Yellow Sea cold water mass in the north China Sea. The average value of virus abundance is 6.36×105VLP·ml-1 in spring,7.22×106 VLP·ml-1 in summer, 2.18×105VLP·ml-1 in autumn,7.51×106VLP·ml-1 in winter. The abundance of virus at the surface water shows obvious difference among four seasons (P<0.01). In horizontal direction, in addition to the winter, virioplankton abundance (VA) of BS and north of NYS is higher than that of south. Vertical distribution of virioplankton in four seasons identical to Yellow Sea cold water mass. The average value of bacteria abundance is 1.84×105 VLP·ml-1 in spring,2.32×106 VLP·ml-1 in summer,1.98×105 VLP·ml-1 in autumn,9.56×105 VLP·ml-1 in winter. The abundance of bacteria shows obvious difference among four seasons (P<0.01). In horizontal direction, heterotrophic bacteria abundance (BA) of BS and north of NYS is higher than that of south except autumn. In addition to the autumn, surface abundance of heterotrophic bacteria is higher than that of bottom.The average value of synechococcus abundance is 1.09×104VLP·ml-1 in spring,2.39×104 VLP·ml-1 in summer,1.38×104VLP·ml-1 in autumn,3.34×10 VLP·ml-1 in winter. The abundance of synechococcus shows obvious difference among four seasons(P< 0.01). In horizontal direction, expect in summer, synechococcus abundance of BS and north of NYS is higher than that of south. In vertical distribution, each water layer synechococcus abundance show significant differences in four seasons. The average value of picoeukaryote abundance is 1.87×104VLP·ml-1 in spring,4.75×103VLP·ml-1 in summer,1.68×103VLP·ml-1 in autumn,8.29×102VLP·ml-1 in winter. The abundance of picoeukaryote shows obvious difference among four seasons(P<0.01). In horizontal direction, picoeukaryote abundance of BS and north of NYS is higher than those of south. In addition to the autumn, surface abundance of picoeukaryote is higher than that of bottom.PCA analysis shows that significant differences were existed in four seasons in both virioplankton and environmental conditions in study areas. Also, the environmental data revealed that, among three areas, significant difference was found expect in spring. However, variation of virioplankton only exhibited clear differences among three areas in spring. Seasonal distribution of virioplankton was affected by a combination of environmental variables (nitrite, phosphate, silicate, salinity and heterotrophic bacteria). In spring and autumn, horizontal distribution of virioplankton was strongly correlated with heterotrophic bacteria.