Multiple drivers of production and particle export in the western tropical North Atlantic

• Published in: Limnology and Oceanography
• Main Authors: Korte, Laura F., Brummer, Geert Jan A., van der Does, Michèlle, Guerreiro, Catarina V., Mienis, Furu, Munday, Chris I., Ponsoni, Leandro, Schouten, Stefan, Stuut, Jan Berend W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2020
• Subjects: /dk/atira/pure/sustainabledevelopmentgoals/life_below_water; name=SDG 14 - Life Below Water; North Atlantic
• Online Access: https://research.vu.nl/en/publications/36921e22-6672-4213-9782-8b1f612b3964; https://doi.org/10.1002/lno.11442; https://hdl.handle.net/1871.1/36921e22-6672-4213-9782-8b1f612b3964; http://www.scopus.com/inward/record.url?scp=85084659166&partnerID=8YFLogxK; http://www.scopus.com/inward/citedby.url?scp=85084659166&partnerID=8YFLogxK

To assess the impacts of Amazon River discharge, Saharan dust deposition, N 2 -fixation and mixed-layer deepening on the biological carbon pump, sediment traps were moored from October 2012 to November 2013 at two sites in the western tropical North Atlantic (49°W,12°N/57°W,12°N). Particle exports interpreted along with satellite- and Argo-float data show peak fluxes in biogenic silica (31 mg m −2 d −1 ) and organic carbon (25 mg m −2 d −1 ) during the fall of 2013 that were ten to five times higher than any time earlier during the year. These high export fluxes occurred in tandem with high surface chlorophyll a concentrations associated with the dispersal of the Amazon River plume, following retroflection into the North-Atlantic-Counter-Current. High fucoxanthin fluxes (' 80 μg m −2 d −1 ) and low δ 15 N-values (−0.6‰) suggest a large contribution by marine diatom-diazotrophic-associations, possibly enhanced by wet Saharan dust deposition. During summer, the Amazon River plume resulted in high mass fluxes at 57°W that were enriched in biogenic silica but weakly influenced by diazotrophic-associations compared to the fall event at 49°W. High carbonate-carbon fluxes (17 mg m −2 d −1 ) dominated a second single event at 49°W during spring that was likely triggered by mixed-layer deepening. Rain-ratios of BSi/C carb amounted to 1.7 when associated with high export fluxes linked to the Amazon River plume. Compared to an annual average of 0.3, this indicates a more efficient uptake of CO 2 via the biological pump compared to when the plume was absent, hence supporting earlier observations that the Amazon River plume is important for ocean CO 2 sequestration.