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

Type Article
Date 2018-03
Language English
Author(s) Kessouri FaycalORCID1, 2, 3, Ulses Caroline1, Estournel ClaudeORCID1, Marsaleix PatrickORCID1, D'Ortenzio Fabrizio4, Severin Tatiana5, 6, Taillandier Vincent4, Conan Pascal6
Affiliation(s) 1 : Univ Toulouse, CNRS, Lab Aerol, UPS, Toulouse, France.
2 : Univ Calif Los Angeles, Dept Atmospher & Ocean Sci, Los Angeles, CA 90095 USA.
3 : Southern Calif Coastal Water Res Project, Costa Mesa, CA USA.
4 : UPMC Univ Paris 06, Sorbonne Univ, Observ Oceanol, CNRS,LOV, Villefranche Sur Mer, France.
5 : Univ Texas Austin, Marine Sci Inst, Port Aransas, TX USA.
6 : UPMC Univ Paris 06, Sorbonne Univ, CNRS, Lab Oceanog Microbienne LOMIC,Observ Oceanol, Banyuls Sur Mer, France.
Source Journal Of Geophysical Research-oceans (2169-9275) (Amer Geophysical Union), 2018-03 , Vol. 123 , N. 3 , P. 1647-1669
DOI 10.1002/2016JC012669
WOS© Times Cited 22
Note This article also appears in: Dense water formations in the North Western Mediterranean: from the physical forcings to the biogeochemical consequences
Keyword(s) physical-biogeochemical 3-D ocean modeling, western Mediterranean Sea, deep convection, phytoplankton bloom, primary production, carbon deep export

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.

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Kessouri Faycal, Ulses Caroline, Estournel Claude, Marsaleix Patrick, D'Ortenzio Fabrizio, Severin Tatiana, Taillandier Vincent, Conan Pascal (2018). Vertical Mixing Effects on Phytoplankton Dynamics and Organic Carbon Export in the Western Mediterranean Sea. Journal Of Geophysical Research-oceans, 123(3), 1647-1669. Publisher's official version : , Open Access version :