Biological Carbon Pump group

Steering committee: S. Jacquet, L.E. Heimburger, Frederic Le Moigne (CEM); K. Leblanc, D. Lefèvre, S. Bonnet (CYBELE); B. Zakardian (LPOC); F. Armougom, C. Tamburini (MEB), D. Nérini (EMBIO)

Coordinator: C. Tamburini

The rise of atmospheric CO2 concentrations (resulting from the burning of fossil fuels) affects global climate. The oceanic Biological Carbon Pump (BCP), i.e. the biogenic carbon production in the surface ocean, its subsequent export (particles sinking out of the sunlit layer of the ocean) and its remineralization (transformation of organic into dissolved CO2) in the water column, represents an important player of the climate system. Annually, the BCP draws down a CO2 flux comparable in size to anthropogenic emissions (Henson et al., 2011). Consequently, any changes in the BCP strength could exacerbate or dampen changes in our climate (Siegel et al. 2016).

In this context, it is crucial to better characterize the dynamics of production, export and remineralisation of organic matter (OM) in surface and at depth. The downward export flux is mainly controlled by a complex interplay of the surface microbial community, which controls particle structure and size distribution (Guidi et al. 2009). Sinking organic particles represent hotspots of remineralisation whose rates and mechanisms are poorly quantified (Tamburini et al. 2009, Riou et al. 2018) and then poorly or not represented in current biogeochemical models. Particle fluxes and dynamics in the dark ocean are mostly measured via drifting and moored sediment traps, radionuclides or by using imaging techniques (McDonnell et al. 2015, Riley et al. 2012, Le Moigne et al. 2012). However, the amount of sinking OM is generally not sufficient to meet the energy required by prokaryotes to perform observed remineralization rate in the dark ocean, in other words, in the dark ocean, we face a discrepancy between the estimation of biological carbon demand and carbon supply (particles flux) (Steinberg et al. 2008, Burd et al. 2010, Herndl & Reinthaler 2013, Giering et al. 2014).

The MIO BioPump group (Axe Transverse Pompe Biologique du MIO) aims to question our understanding of OM remineralization in the dark ocean as well as basic ecology and metabolism of prokaryotic communities associated to sinking particles.