Diatoms, through their metabolic activities, contribute massively to primary production and recycling of carbon and nitrogen in the ocean. Virus of diatoms are widespread and control diatom population by cell lysis. The impact of infection on diatom metabolism, before lysis occurs, is however unknown. This study aims to evaluate how diatom infection influence the carbon and nitrogen fluxes before cell death. To that purpose, we used a dominant marine diatom, Mediolabrus comicus, and its associated RNA virus. First, we obtained basic metrics of viral infection of M. comicus to optimize the experimental set up. Stable isotopic labels of 13C and 15N were added to non-infected and infected cultures in late exponential growth phase. Diatom abundances, optical properties, photosynthetic efficiency, and nutrient incorporation were recorded during 72h. Diatoms grew well and incorporated on labelled media and δ13C and δ15N. Infection induced mild changes in cell characteristics, notably in their scattering properties (forward scatter) and membrane permeability. Some mild differences were observed in δ13C and δ15N between infected and non-infected cultures, but these changes were not significant. Although promising results were obtained, our experimental set up still needs optimization to accurately quantify the viral impact on nutrients uptakes of infected diatom.
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