Program     Circulation, biogeochemistry and carbon cycling in ocean margins       Poster Viral impact on the growth and mortality of picophytoplankton in the South China Sea, during summer P-M1-08-S Changlin Li* , Xiamen University, China Xin Liu, Xiamen University, China Bangqin Huang, Xiamen University, China Presenter Email: lichanglinxmu@163.com Autotrophic picoplankton are abundant and important primary producers, especially over the vast tropical and subtropical regions of the oceans. Viruses are important mortality agents for marine picophytoplankton. Through the lysis of their autotrophic hosts, viruses regulate primary production and have major efforts on nutrients and energy flow in the ocean. However, to date there are few published studies that have investigated picophytoplankton group-specific viral lysis rates. Using a modification of the seawater dilution approach, we quantify growth and mortality rates for prochlorococcus, synechococcus and picoeukaryotes in the South China Sea during summer. Unlike others studies, our most experiments yield negative rates of viral lysis, i.e. the removal of viruses reduces the growth of the picophytoplankton, either because viruses reduce competition by lysing other populations or enhance growth indirectly by accelerating the recycling of potential growth-limiting nutrients. We also observe a significant negative relationship between viral lysis rate and the abundance of hosts.

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