Vertical Mixing Effects on Phytoplankton Dynamics and Organic Carbon Export in the Western Mediterranean Sea

Type : ACL
Nature : Production scientifique
Au bénéfice du Laboratoire : Oui
Statut de publication : Publié
Année de publication : 2018
Auteurs (8) : KESSOURI Fayçal ULSES Caroline ESTOURNEL Claude MARSALEIX Patrick D'ORTENZIO Fabrizio SEVERIN Tatiana TAILLANDIER Vincent CONAN Pascal
Revue scientifique : Journal of Geophysical Research-Oceans
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Fascicule :
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DOI : 10.1002/2016JC012669
URL : https://doi.org/10.1002/2016jc012669
Abstract : A 3‐D high‐resolution coupled hydrodynamic‐biogeochemical model of the western Mediterranean was used to study phytoplankton dynamics and organic carbon export in three regions with contrasting vertical regimes, ranging from deep convection to a shallow mixed layer. One month after the initial increase in surface chlorophyll (caused by the erosion of the deep chlorophyll maximum), the autumnal bloom was triggered in all three regions by the upward flux of nutrients resulting from mixed layer deepening. In contrast, at the end of winter, the end of turbulent mixing favored the onset of the spring bloom in the deep convection region. Low grazing pressure allowed rapid phytoplankton growth during the bloom. Primary production in the shallow mixed layer region, the Algerian subbasin, was characterized by a long period (4 months) of sustained phytoplankton development, unlike the deep convection region where primary production was inhibited during 2 months in winter. Despite seasonal variations, annual primary production in all three regions is similar. In the deep convection region, total organic carbon export below the photic layer (150 m) and transfer to deep waters (800 m) was 5 and 8 times, respectively, higher than in the Algerian subbasin. Although some of the exported material will be injected back into the surface layer during the next convection event, lateral transport, and strong interannual variability of MLD in this region suggest that a significant amount of exported material is effectively sequestrated.
Mots-clés : physical‐biogeochemical 3‐D ocean modeling; western Mediterranean Sea; deep convection; phytoplankton bloom; primary production; carbon deep export
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Citation :
Kessouri F, Ulses C, Estournel C, Marsaleix P, D'Ortenzio F, Severin T, Taillandier V, Conan P (2018) Vertical Mixing Effects on Phytoplankton Dynamics and Organic Carbon Export in the Western Mediterranean Sea. J Geophys Res-Oceans | doi: 10.1002/2016JC012669