The biogeochemistry of cobalt in the Mediterranean Sea

Type Article
Date 2017-02
Language English
Author(s) Dulaquais Gabriel1, Planquette HeleneORCID1, L'Helguen Stephane1, Rijkenberg Micha J. A.2, Boye Marie1
Affiliation(s) 1 : Univ Bretagne Occidentale, Lab Sci Environm Marin, CNRS UMR 6539, Inst Univ Europeen Mer, Plouzane, France.
2 : Univ Utrecht, NIOZ Royal Netherlands Inst Sea Res, Dept Ocean Syst, Den Burg, Netherlands.
Source Global Biogeochemical Cycles (0886-6236) (Amer Geophysical Union), 2017-02 , Vol. 31 , N. 2 , P. 377-399
DOI 10.1002/2016GB005478
WOS© Times Cited 17

The soluble (sCo < 0.02 mu m), dissolved (DCo < 0.2 mu m), colloidal (cCo, as DCo minus sCo), and the particulate ( pCo > 0.2 mu m) fractions of cobalt were investigated along the GEOTRACES-A04 section. Our results show that sCo was the predominant form (90%) of the DCo in the Mediterranean Sea and that cCo and pCo generally followed the same distribution, suggesting a biogeochemical link between these two fractions. In the Mediterranean Sea, DCo displayed an overall scavenged-like profile in the different sub- basins, with high concentrations (up to 350 pM) in surface and quasi-uniformed low concentrations of DCo (similar to 45 pM) in the deep sea. However, the decoupling between the surface and the deep reservoirs suggested that the transfer of Co from dissolved to particulate pools during the sink of particles may not be the only process governing DCo distribution. High-surface Co inputs, stabilization of DCo in a soluble form, and the extremely high regeneration rate of biogenic pCo all lead to the accumulation of DCo in surface. Conversely, low pCo export from the surface waters, low remineralization of biogenic pCo, and slow but efficient removal of DCo by scavenging including colloid aggregation into particles prevented its accumulation in the intermediate and deep sea. Moreover, Mediterranean circulation prevented the exchanges between the DCo-rich surface and the DCo-poor deep layers enhancing the scavenged-like profile of DCo. Finally, tentative DCo budgets were balanced at basin scale and showed the strong imprint of the surface inputs at Gibraltar Strait on the Mediterranean cobalt biogeochemistry.

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