| Summary: | Scientific Committee on Antarctic Research Open Science Conference (SCAR 2020), 3-7 August 2020 During the winter season, sea-ice is a refuge of Antarctic microbial communities including phytoplankton, heterotrophic protists, bacteria and viruses. Then, along summer, due to sea ice melting, those microorganisms are released to the water and their metabolism and trophic interactions play a key role in the biogeochemical cycles in the ocean. Viral infections on microorganisms produce large quantities of dissolved and particulate organic matter (OM) including cell debris and other colloidal material. This OM may be incorporated in bubble-mediated spray production forming cooling marine aerosols and cloud layers potentially affecting climate. We therefore, tested experimentally the effect of viral lysis on bacteria, heterotrophic protists and phytoplankton, and their contribution to the production of aerosol precursors compounds during a field study carried out near the Antarctic peninsula in February 2019 using fixed and mobile platforms. We performed four experiments on melted sea ice incubated for 48-72 h in 60 L mesocosm (using two treatments: unamended natural viruses and viral addition) and subjected to still and bubbled periods. The generated aerosols were monitored by on-line and off-line aerosol techniques. Our results -systematically for all fourexperiments -showed that after viral addition the microbial mortality (rate of lysed cells/mL/ d) increased. Concurrently, the released organic C, N, P augmented and significantly correlate with the concentration of dissolved organic carbon measured in the sea ice samples. We discuss that our data support the crucial role of virus mediated lysis of microbes on sea-ice-ocean-atmosphere interactions, including aerosol particle production Peer reviewed
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