We are proposing an MSc internship (2nd year) for a duration of 6 months to study the role of diversity in virus-microbe communities on ocean carbon dynamics.
Context: Marine microorganisms play a key role in the biogeochemistry of the ocean. Photosynthetic microorganisms transform dissolved inorganic CO2 into organic matter, part of which is exported and sequestered as particulate organic matter (POM) in the deep ocean. These processes drive the biological carbon pump (BCP). During the sedimentation of the POM, heterotrophic bacteria remineralize the organic matter into inorganic matter hence reducing the flow of carbon export.
Photosynthetic and heterotrophic microbes can be infected by marine viruses. Through this infection, viruses affect marine microbial dynamics and the functioning of the BCP. Yet, little is known about the net effect of viruses on the carbon export flow into the deep ocean. To date, two main hypotheses have been proposed: 1) the viral shunt, where viral lysis shunts the carbon flow from the BCP to lower microbial realms where remineralization from bacteria reduces the flow of POM and 2) the viral shuttle, where viral lysis may produce sticky chemical compounds that increase particle aggregation and carbon export.
This project aims to study the impact of viral and microbial diversity and dynamics on the carbon export potential of the BCP. To do so, we will couple simple ecological models describing the interaction of viruses and their microbial hosts with a simple biogeochemical model representing key processes of the BCP.
Objectives: The student will first build a community model describing virus-microbe dynamics. Second, they will incorporate different taxonomic levels with heterotrophic bacteria, phytoplankton, and zooplankton communities. Finally, the student will design a simple biophysical model to describe particle aggregation and link it with virus lysis. This model will allow them to study the impact of microbe-virus dynamics and their diversity on the dynamics of the viral shunt and the viral shuttle.
Supervision: The student will be supervised by Dr. David Demory (CR CNRS, BIOM, UMR7232) and Dr. Bart Haegeman (CR CNRS, LOMIC, UMR7621) from the Oceanological Observatory of Banyuls/mer. BH is a physicist working on ecological dynamics with a particular focus on the impact of community diversity on ecological function across scales. DD is a theoretical ecologist and oceanographer, specializing in virus-microbe ecological dynamics.
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