Help Privacy Policy Disclaimer
  Advanced SearchBrowse


  Biogeochemical cycling of cadmium isotopes in the Southern Ocean along the Zero Meridian

Abouchami, W., Galer, S. J. G., de Baar, H. J. W., Middag, R., Vance, D., Zhao, Y., et al. (2014). Biogeochemical cycling of cadmium isotopes in the Southern Ocean along the Zero Meridian. Geochimica et Cosmochimica Acta, 127, 348-367. doi:10.1016/j.gca.2013.10.022.

Item is


show Files




Abouchami, W.1, Author              
Galer, S. J. G.1, Author              
de Baar, H. J. W.2, Author
Middag, R.2, Author
Vance, D.2, Author
Zhao, Y.2, Author
Klunder, M.2, Author
Mezger, K.2, Author
Feldmann, H.1, Author              
Andreae, M. O.1, Author              
1Biogeochemistry, Max Planck Institute for Chemistry, Max Planck Society, ou_1826286              
2external, ou_persistent22              


Free keywords: -
 Abstract: We present depth profiles of Cd isotopes and concentrations from the Southern Ocean at four stations in the Atlantic sector along the Greenwich Meridian (47 degrees S to 68 degrees S) located across the main Antarctic frontal zones and productivity belt. The vertical profiles of Cd concentration typically show low values in surface waters, elevated values at intermediate depths, reflecting remineralization of sinking particulate organic matter, and constant values in deep waters. The surface-to-deep isotopic gradient shows "heavy" Cd isotope signatures in the mixed surface layer, becoming more pronounced northward, with values up to epsilon(112/110) Cd of around +4.1 in the Subantarctic sector of the Southern Ocean. Deep Antarctic waters display a uniform and "light" epsilon(112/110) Cd of +1.18 +/- 0.38 and Cd concentrations of 0.761 +/- 0.101 nmol/kg (n = 23, 2SD). Intermediate waters are characterized by epsilon(112/110) Cd lying between those of surface and deep waters, with a constant value of about +0.8 in the High Nutrient Low Chlorophyll sector and a notably higher value of +2.3 in the Subantarctic sector. The Cd isotope fractionation in the Southern Ocean closely follows a simple closed-system Rayleigh model, in which biological uptake of Cd imparts the epsilon(112/110) Cd signature to the surface layer while that of deep waters is determined by the flux of regenerated isotopically-light Cd from sinking organic matter from the surface ocean and the degree of mixing of distinct water masses. The vertical gradient documented for Cd isotopes and nutrient ratios, along with the meridional gradient in surface waters, highlights the important role played by upwelling in the Southern Ocean in closing the meridional overturning circulation via the export of Antarctic intermediate and mode waters which have a distinctive chemical (low Cd:P) and Cd isotope ("heavy") signature. The combined Cd-Zn isotope systematics provide evidence for a strong link between the magnitude of biological Cd stable isotope fractionation and Zn availability in the contrasted nutrient and ecological regimes of the Southern Ocean. Substitution of Cd for Zn in the enzyme carbonic anhydrase appears to be the driving mechanism for Cd isotope fractionation in the Antarctic Circumpolar Current, while an "excess-uptake" mechanism seems to predominate in the Weddell Gyre. Our study highlights some of the complexities of the biogeochemical cycling of Cd in the oceans. Nevertheless, systematic variations in Cd isotopic compositions with water mass distribution in the Southern Ocean suggest that Cd isotopes could, with some caveats, be useful tracers of changes in past nutrient utilization and deep water circulation. (C) 2013 Elsevier Ltd. All rights reserved.


 Dates: 2014
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: -
 Identifiers: ISI: 000329842900021
DOI: 10.1016/j.gca.2013.10.022
 Degree: -



Legal Case


Project information


Source 1

Title: Geochimica et Cosmochimica Acta
Source Genre: Journal
Publ. Info: Oxford : Pergamon
Pages: - Volume / Issue: 127 Sequence Number: - Start / End Page: 348 - 367 Identifier: ISSN: 0016-7037