[A-OS13] Marine ecosystems and biogeochemical cycles: theory, observation and modeling

[AOS13-01] Impacts of viral infections and ecosystem variability on the marine Carbon cycle

★Invited Papers

*Marie-Fanny Racault¹, Corinne Le Quéré¹, Erik Buitenhuis¹, Rebecca Wright¹, Lionel Guidi², Fabien Lombard² (1.School of Environmental Sciences, University of East Anglia, Norwich Research Park, NR4 7TJ Norwich, UK , 2.Sorbonne Université, CNRS, Laboratoire d'Océanographie de Villefranche, Villefranche-sur-Mer, France)

Keywords:ecosystem modelling, marine viruses , biogeochemical cycles, carbon export, microbial recycling, observational datasets

Viruses are the most abundant entities of marine ecosystems. They have a profound impact on marine communities’ diversity and biogeochemical cycling. In the ocean, viral infections are responsible for the death of about 1/3 of microbial cells per day, and cause, at the global scale, the transfer of ~25% of primary production into the pool of dissolved organic carbon (DOC). This process, referred to as the ‘viral shunt’, can influence nutrient cycling, and reduce both food supply to higher trophic levels and carbon flux from the surface to the deep oceans. Complementary to this recycling process, viral lysates can also aggregate into larger particles, and increase the vertical flux of particulate organic carbon (POC) to depth, referred to as the ‘viral shuttle’. Estimates based on new observation capabilities and analysis techniques using ‘omics and imaging data have shown that changes in viral communities can impact > 65% of the carbon export efficiency worldwide. Yet, to date, viral infections are completely absent from all Earth System Models.
Here, we develop the first marine-viruses component in the global biogeochemical model PlankTOM that incorporates the ecology of multi-plankton functional groups (from bacteria to macro-zooplankton). We exploit very large and high-resolution imaging (UVP), genomic, and satellite datasets along with published observational and experimental studies to characterise viral processes (i.e., viral shunt and shuttle) and their effects on marine Carbon recycling and export. This data integration is further used to produce and validate new representations of diverse marine ecosystem structures and assess their impacts on Carbon export fluxes. Finally, we analyse the model results to quantify the extent to which viral infections control the spatio-temporal distributions of primary producers, grazers and bacterial recycling, and in doing so, modulate ocean’s carbon uptake capacity.