Remineralization of Organic particles in Presence of Ballast MInerals (ROBIN)
The project aims at understanding the complex interaction between mineral and sinking organic carbon in the ocean, in the context of the biological carbon pump (BCP). The BCP annually transfers 5-15 GT C yr-1 from the atmosphere to the ocean’s interior in the form of sinking particles with an organic component. As these particles sink they are remineralised with the constituent elements (incl. Carbon) returning to solution. If a link exists between the particles remineralisation depth and their mineral concentration (calcite, opal or dust), we can expect changes in air-sea CO2 partitioning resulting from ocean acidification and/or change in aerosol deposition. It is therefore critical to understand the factors regulating remineralisation depth if one wants to assess how ocean biological processes respond to and contribute to regulate the global climate. To date, no direct in situ observation of OM remineralisation depth combined with the assessment of the mineral content of sinking particles has been performed. Controled experiments in the lab, as well as two field experiments (in the North Atlantic Porcupine Abyssal Plain, and the Mediterranean Sea) will be undertaken during ROBIN. We will evaluate the role of ballast minerals in regulating particle decomposition in the mesopelagic zone using pressurized incubation chambers (PASS-PArticles Sinking Simulator) and modified sediment traps (Marine Snow Catcher, lent by the National Oceanography Centre). The ROBIN project is structured around two objectives: (i) Determine whether organic carbon mineralization rate is a function of mineral to organic carbon ratios in sinking particles and (ii) Assessing whether or not bacteria and/or ectoenzymes are excluded from within mineral associated particles.