The biogeochemistry of cobalt in the Mediterranean Sea
Dulaquais, G.; Planquette, H.; L'Helguen, S.; Rijkenberg, M.J.A.; Boye, M. (2017). The biogeochemistry of cobalt in the Mediterranean Sea. Global Biogeochem. Cycles 31: 377-399. dx.doi.org//10.1002/2016gb005478
In: Global Biogeochemical Cycles. American Geophysical Union: Washington, DC. ISSN 0886-6236; e-ISSN 1944-9224, more
The soluble (sCo<0.02 μm), dissolved (DCo<0.2 μm), colloidal (cCo, as DCo minus sCo), and theparticulate (pCo>0.2 μm) fractions of cobalt were investigated along the GEOTRACES-A04 section. Ourresults show that sCo was the predominant form (90%) of the DCo in the Mediterranean Sea and that cCo andpCo 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, withhigh concentrations (up to 350 pM) in surface and quasi-uniformed low concentrations of DCo (~45 pM) inthe deep sea. However, the decoupling between the surface and the deep reservoirs suggested that thetransfer of Co from dissolved to particulate pools during the sink of particles may not be the only processgoverning DCo distribution. High-surface Co inputs, stabilization of DCo in a soluble form, and the extremelyhigh regeneration rate of biogenic pCo all lead to the accumulation of DCo in surface. Conversely, low pCoexport from the surface waters, low remineralization of biogenic pCo, and slow but efficient removal of DCoby scavenging including colloid aggregation into particles prevented its accumulation in the intermediateand deep sea. Moreover, Mediterranean circulation prevented the exchanges between the DCo-rich surfaceand the DCo-poor deep layers enhancing the scavenged-like profile of DCo. Finally, tentative DCo budgetswere balanced at basin scale and showed the strong imprint of the surface inputs at Gibraltar Strait on theMediterranean cobalt biogeochemistry.
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