The main objective is to investigate the transfer of particulate organic mater and nutrients from the surface towards the deeper ocean both in continental margin and open sea settings. The control mechanisms and forcing conditions of this process will be studied as they are the input needed to pin down the capacity of the marine environment of absorbing carbon and withdrawing it from the atmosphere. To address this issue three contrasted sites have been chosen: one oligotrophic-mesotrophic site at the Ligurian Sea, one site southwest of the island of Gran Canaria affected by the Canary Current and Saharan atmospheric inputs and the continental margin at the Gulf of Lions,
In both open sea sites investigations a multi-tracer approach will be used to test that:
a) ballast minerals physically protect a fraction of their associated total organic matter, which persists to predominate over the unprotected fraction in the lower (>1000m) part of the water column. And
b) the ratio of organic carbon to ballast is key to predicting variability in export fluxes, deep fluxes, sinking velocities, and remineralisation of particulate organic carbon.
This multi-tracer approach will be conducted on samples collected with sediment traps at 4 different depths at the Ligurian Sea site and at 3 different depths at the Canary current site In the continental margin site transfer near the bottom and along canyons will be studied by analysing the material collected by sequential sediment traps located at 30 meters above the bottom at 7 different locations. Sediment traps samples will be analysed for major constituent composition in order to characterise the collected material and estimate flux variability. Organic matter characterisation analyses will be performed to trace the pathways and processes that affect organic matter during its transfer.
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