References

Biogeosciences

1726-4189

Copernicus Publications

Göttingen, Germany

10.5194/bg-4-181-2007

Sources and transport of dissolved iron and manganese along the continental margin of the Bay of Biscay

Laës

⁶ ¹ Blain

² Laan

³ Ussher

S. J.

⁴ Achterberg

E. P.

⁵ Tréguer

¹ de Baar

H. J. W.

Institut Universitaire Européen de la Mer, LEMAR UMR CNRS 6539, Place Nicolas Copernic, 29280 Plouzané, France

Centre d'Océanologie de Marseille, LOB UMR CNRS 6535, campus de Luminy, case 901, 13288 Marseille Cedex, France

Royal Netherlands Institute for Sea Research (NIOZ), Texel, The Netherlands

School of Earth, Ocean and Environmental Science, University of Plymouth, PL4 8AA Plymouth, UK

National Oceanography Centre Southampton, University of Southampton, SO14 3ZH Southampton, UK

now at: Ifremer, Département TSI, Centre de Brest, BP 70, 29280 Plouzané, France

14 03 2007

4 2 181 194

2007

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Dissolved iron (DFe; <0.2 µm) and dissolved manganese (DMn; <0.2 µm) concentrations were determined in the water column of the Bay of Biscay (eastern North Atlantic Ocean) in March 2002. The samples were collected along a transect traversing from the European continental shelf over the continental slope. The highest DFe and DMn concentrations (2.39 nM and 6.10 nM, respectively) were observed in the bottom waters on the shelf at stations closest to the coast. The release of trace metal from resuspended particles and the diffusion from pore waters were probably at the origin of elevated DFe and DMn concentrations in the Bottom Boundary Layer (BBL). In the slope region, the highest total dissolvable iron (TDFe), DFe and DMn values (24.6 nM, 1.58 nM and 2.12 nM, respectively) were observed close to the bottom at depth of ca.~600–700 m. Internal wave activity and slope circulation are thought to be at the origin of this phenomenon. These processes were also very likely the cause of elevated concentrations (DFe: 1.27 nM, DMn: 2.34 nM) measured in surface waters of stations located in the same area. At stations off the continental slope, the vertical distribution of both metals were typical of open ocean conditions, indicating that inputs from the continental margin did not impact the metal distributions in the offshore waters.

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