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Sources of dissolved iron to oxygen minimum zone waters on the Senegalese continental margin in the tropical North Atlantic Ocean: Insights from iron isotopes

Sources of dissolved iron to oxygen minimum zone waters on the Senegalese continental margin in the tropical North Atlantic Ocean: Insights from iron isotopes
Sources of dissolved iron to oxygen minimum zone waters on the Senegalese continental margin in the tropical North Atlantic Ocean: Insights from iron isotopes
Oxygen minimum zones (OMZs) cover extensive areas of eastern boundary ocean regions and play an important role in the cycling of the essential micronutrient iron (Fe). The isotopic composition of dissolved Fe (dFe) in shelf and slope waters on the Senegalese margin was determined to investigate the processes leading to enhanced dFe concentrations (up to 2 nM) in this tropical North Atlantic OMZ. On the shelf, the δ56Fe value of dFe (relative to the reference material IRMM-014) was as low as -0.33 ‰, which can be attributed to input of dFe from both reductive and nonreductive dissolution of sediments. Benthic inputs of dFe are subsequently upwelled to surface waters and recycled in the water column by biological uptake and remineralisation processes. Remineralised dFe is characterised by relatively high δ56Fe values (up to +0.41 ‰), and the contribution of remineralised Fe to the total dFe pool increases with distance from the shelf. Remineralisation plays an important role in the redistribution of dFe that is mainly supplied by benthic and atmospheric inputs, although dust inputs, estimated from dissolved aluminium concentrations, were low at the time of our study (2 to 9 nmol dFe m-2 d-1). As OMZs are expected to expand as climate warms, our data provide important insights into Fe sources and Fe cycling in the tropical North Atlantic Ocean.
0016-7037
James, Rachael
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Klar, Jessica
27637ace-8fd9-4859-adb3-a308b58a827e
Milton, James
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Schlosser, C.
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Woodward, M.
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Lacan, Francois
d0093c6f-dacb-4a97-9c57-57413d36631f
Parkinson, Ian
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Achterberg, Eric
685ce961-8c45-4503-9f03-50f6561202b9
James, Rachael
79aa1d5c-675d-4ba3-85be-fb20798c02f4
Klar, Jessica
27637ace-8fd9-4859-adb3-a308b58a827e
Milton, James
9e183221-d0d4-4ddb-aeba-0fdde9d31230
Schlosser, C.
7990a0cc-cfe9-4dd5-9c45-899c03186207
Woodward, M.
c9d7039c-6bef-4e99-b420-fbee1f675a14
Lacan, Francois
d0093c6f-dacb-4a97-9c57-57413d36631f
Parkinson, Ian
fbf4a823-b4fd-465e-921e-772b342d0d10
Achterberg, Eric
685ce961-8c45-4503-9f03-50f6561202b9

James, Rachael, Klar, Jessica, Milton, James, Schlosser, C., Woodward, M., Lacan, Francois, Parkinson, Ian and Achterberg, Eric (2018) Sources of dissolved iron to oxygen minimum zone waters on the Senegalese continental margin in the tropical North Atlantic Ocean: Insights from iron isotopes. Geochimica et Cosmochimica Acta. (doi:10.1016/j.gca.2018.02.031).

Record type: Article

Abstract

Oxygen minimum zones (OMZs) cover extensive areas of eastern boundary ocean regions and play an important role in the cycling of the essential micronutrient iron (Fe). The isotopic composition of dissolved Fe (dFe) in shelf and slope waters on the Senegalese margin was determined to investigate the processes leading to enhanced dFe concentrations (up to 2 nM) in this tropical North Atlantic OMZ. On the shelf, the δ56Fe value of dFe (relative to the reference material IRMM-014) was as low as -0.33 ‰, which can be attributed to input of dFe from both reductive and nonreductive dissolution of sediments. Benthic inputs of dFe are subsequently upwelled to surface waters and recycled in the water column by biological uptake and remineralisation processes. Remineralised dFe is characterised by relatively high δ56Fe values (up to +0.41 ‰), and the contribution of remineralised Fe to the total dFe pool increases with distance from the shelf. Remineralisation plays an important role in the redistribution of dFe that is mainly supplied by benthic and atmospheric inputs, although dust inputs, estimated from dissolved aluminium concentrations, were low at the time of our study (2 to 9 nmol dFe m-2 d-1). As OMZs are expected to expand as climate warms, our data provide important insights into Fe sources and Fe cycling in the tropical North Atlantic Ocean.

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Accepted/In Press date: 17 February 2018
e-pub ahead of print date: 2 March 2018

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Local EPrints ID: 418584
URI: http://eprints.soton.ac.uk/id/eprint/418584
ISSN: 0016-7037
PURE UUID: 4a40559a-cb3c-4bd0-ad85-bdaac35f9c31

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Date deposited: 12 Mar 2018 17:30
Last modified: 16 Dec 2019 18:24

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Contributors

Author: Rachael James
Author: Jessica Klar
Author: James Milton
Author: C. Schlosser
Author: M. Woodward
Author: Francois Lacan
Author: Ian Parkinson
Author: Eric Achterberg

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