Particulate barium tracing of significant mesopelagic carbon remineralisation in the North Atlantic ...

• Main Authors: Lemaitre, Nolwenn, Planquette, Helene, Planchon, Frédéric, Sarthou, Géraldine, Jacquet, Stéphanie, García-Ibáñez, Maribel I., Gourain, Arthur, Cheize, Marie, Monin, Laurence, André, Luc, Laha, Priya, Terryn, Herman, Dehairs, Frank
• Format: Text
• Language: English
• Published: ETH Zurich 2018
• Subjects: Labrador Sea; North Atlantic
• Online Access: https://dx.doi.org/10.3929/ethz-b-000261743; http://hdl.handle.net/20.500.11850/261743

The remineralisation of sinking particles by prokaryotic heterotrophic activity is important for controlling oceanic carbon sequestration. Here, we report mesopelagic particulate organic carbon (POC) remineralisation fluxes in the North Atlantic along the GEOTRACES-GA01 section (GEOVIDE cruise; May–June 2014) using the particulate biogenic barium (excess barium; Baxs) proxy. Important mesopelagic (100–1000 m) Baxs differences were observed along the transect depending on the intensity of past blooms, the phytoplankton community structure, and the physical forcing, including downwelling. The subpolar province was characterized by the highest mesopelagic Baxs content (up to 727 pmol L−1), which was attributed to an intense bloom averaging 6 mg chl a m−3 between January and June 2014 and by an intense 1500 m deep convection in the central Labrador Sea during the winter preceding the sampling. This downwelling could have promoted a deepening of the prokaryotic heterotrophic activity, increasing the Baxs content. ... : Biogeosciences, 15 (8) ...