Frederic Le Moigne

Global models predict a decline in dissolved oxygen concentrations and a consequent expansion of the Oxygen Minimum Zones (OMZs) in the future ocean. A detailed mechanistic understanding of the biogeochemistry of OMZs is therefore critical to allow predictions of oceanic processes under future climate conditions-. The biological carbon pump (BCP) constitutes a crucial biogeochemical mechanism which of carbon is transferred from the surface to the deep ocean. The BCP exports organic matter in the forms of sinking particles and dissolved compounds to the deep ocean where it is sequestered over geological time scales. There is currently no consensus on the fate of sinking OM and the efficiency of the BCP in OMZ areas. Previous particles flux studies have shown that the BCP is more efficient in suboxic zones relative to well- oxygenated waters in close vicinity. However, incubation experiments performed using sinking material collected in oxic and suboxic areas have indicated similar remineralisation rates under both conditions suggesting that suboxic conditions do not facilitate the transfer of sinking OM through the mesopelagic zone (below the euphotic zone to 1000m). This project will assess how different oxygen conditions and surface ocean productivity levels impact C:N:P remineralization rates of sinking particles. I propose to measure remineralization rate of sinking particles collected at multiple depths using large water volume collection devices and specialized remineralization incubation chambers. I will participate on Kiel based project SFB 754 related cruise in the equatorial Pacific OMZ off the shelf of Peru. I will then investigate the relationships between oxygen levels and C:N:P remineralization rates and contribute to an improved parameterisation of the BCP in biogeochemical models of the OMZ. Overall, this project aims to provide an improved description the BCP in low oxygen ocean regions.