Deposition events of anthropogenic aerosols from East Asia, containing both inorganic nutrients and organic matters, have a comprehensive effect on the ecosystem of China's marginal seas. However, the effects of such deposition on viruses, which are essential for the ocean, are not yet fully understood. In this study, by conducting on-board microcosm experiments in two distinct ecosystems in the China's marginal seas (the South China Sea and the East China Sea), we investigated the response of viruses to atmospheric deposition events in terms of abundance, activity, community structure, and functional genes for the first time. Although the structure of viral communities shows geographical specificity, the survival strategies and diversity of virus exhibited similar responses to anthropogenic aerosol addition in the two sea areas. It was found that anthropogenic aerosol input slightly increased the abundance of lytic virus, indicating that the aerosol nutrients has improved the survival environment of viruses by relieving nutrient limitation of their hosts, although the total viral abundance reduced significantly. The abundance of nucleocytoplasmic large DNA viruses (NCLDVs) infecting eukaryotic hosts increased, which is believed to be linked to the increase in abundances of their hosts such as eukaryotic phytoplankton and protozoa. Additionally, the abundance of protein families related to eukaryotes and NCLDVs also increased significantly. The α-diversity (i.e., Shannon index, Chao richness) of virus decreased after aerosol addition, but viral production displayed vary trends in different sea areas. Changes of viral community composition were also reflected in the auxiliary metabolic genes (AMGs) encoded by viruses, which showed different trends at different stations after adding aerosols. These Virus-encoded AMGs can either promote or inhibit carbon, nitrogen, sulfur, and phosphorus-related metabolic functions to varying degrees in response to atmospheric deposition events. This study suggested that anthropogenic aerosol deposition, which introduces external nutrients, can potentially influence marine viral communities and their functional capabilities, and thus have a significant impact on dynamics and function of microbial food web.

atmospheric deposition, viral production, viral community composition, DNA virus, RNA virus