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A tale of two gyres: contrasting distributions of dissolved cobalt and iron in the Atlantic Ocean during an Atlantic Meridional Transect (AMT-19)

A tale of two gyres: contrasting distributions of dissolved cobalt and iron in the Atlantic Ocean during an Atlantic Meridional Transect (AMT-19)
A tale of two gyres: contrasting distributions of dissolved cobalt and iron in the Atlantic Ocean during an Atlantic Meridional Transect (AMT-19)
Cobalt (Co) and iron (Fe) are essential for phytoplankton nutrition, and as such constitute a vital link in the marine biological carbon pump. Atmospheric deposition is an important, and in some places the dominant, source of trace elements (TEs) to the global ocean. Dissolved cobalt (dCo) and iron (dFe) were determined along an Atlantic Meridional Transect (AMT-19; Oct/Nov 2009) between 50°N and 40°S in the upper 150 m in order to investigate the behaviour and distribution of these two essential, bioactive TEs. During AMT-19, large differences in the distributions of dCo and dFe were observed. In the North Atlantic gyre provinces, extremely low mixed layer dCo concentrations (23 ± 9 pM) were observed, which contrasts with the relatively high mixed layer dFe concentrations (up to 1.0 nM) coincident with the band of highest atmospheric deposition (∼5–30°N). In the South Atlantic gyre, the opposite trend was observed, with relatively high dCo (55 ± 18 pM) observed throughout the water column, but low dFe concentrations (0.29 ± 0.08 nM). Given that annual dust supply is an order of magnitude greater in the North than the South Atlantic, the dCo distribution was somewhat unexpected. However, the distribution of dCo shows similarities with the distribution of phosphate (PO43−) in the euphotic zone of the Atlantic Ocean, where the North Atlantic gyre is characterised by chronically low PO4, and higher concentrations are observed in the South Atlantic gyre (Mather et al., 2008), suggesting the potential for a similar biological control of dCo distributions. Inverse correlations between dCo and Prochlorococcus abundance in the North Atlantic gyre provinces, combined with extremely low dCo where nitrogen fixation rates were highest (∼20–28°N), suggests the dominance of biological controls on dCo distributions. The contrasting dCo and dFe distributions in the North and South Atlantic gyres provides insights into the differences between the dominant controls on the distribution of these two bioactive trace metals in the central Atlantic Ocean.
0079-6611
52-64
Shelley, Rachel U.
da7abad3-b5c8-4e11-aeda-7a0256a6fab9
Wyatt, Neil J.
258d214b-9dae-4a5f-acc9-c0a55fb66efd
Tarran, Glenn A.
590096f3-1c5c-4f60-b9d3-9c1f75a80668
Rees, Andrew P.
5971ea8f-f7ee-4556-b8b2-8ffc4b52d2c5
Worsfold, Paul J.
27675f89-7eee-45c5-821e-a381d8db9693
Lohan, Maeve C.
6ca10597-2d0f-40e8-8e4f-7619dfac5088
Shelley, Rachel U.
da7abad3-b5c8-4e11-aeda-7a0256a6fab9
Wyatt, Neil J.
258d214b-9dae-4a5f-acc9-c0a55fb66efd
Tarran, Glenn A.
590096f3-1c5c-4f60-b9d3-9c1f75a80668
Rees, Andrew P.
5971ea8f-f7ee-4556-b8b2-8ffc4b52d2c5
Worsfold, Paul J.
27675f89-7eee-45c5-821e-a381d8db9693
Lohan, Maeve C.
6ca10597-2d0f-40e8-8e4f-7619dfac5088

Shelley, Rachel U., Wyatt, Neil J., Tarran, Glenn A., Rees, Andrew P., Worsfold, Paul J. and Lohan, Maeve C. (2017) A tale of two gyres: contrasting distributions of dissolved cobalt and iron in the Atlantic Ocean during an Atlantic Meridional Transect (AMT-19). Progress in Oceanography, 158, 52-64. (doi:10.1016/j.pocean.2016.10.013).

Record type: Article

Abstract

Cobalt (Co) and iron (Fe) are essential for phytoplankton nutrition, and as such constitute a vital link in the marine biological carbon pump. Atmospheric deposition is an important, and in some places the dominant, source of trace elements (TEs) to the global ocean. Dissolved cobalt (dCo) and iron (dFe) were determined along an Atlantic Meridional Transect (AMT-19; Oct/Nov 2009) between 50°N and 40°S in the upper 150 m in order to investigate the behaviour and distribution of these two essential, bioactive TEs. During AMT-19, large differences in the distributions of dCo and dFe were observed. In the North Atlantic gyre provinces, extremely low mixed layer dCo concentrations (23 ± 9 pM) were observed, which contrasts with the relatively high mixed layer dFe concentrations (up to 1.0 nM) coincident with the band of highest atmospheric deposition (∼5–30°N). In the South Atlantic gyre, the opposite trend was observed, with relatively high dCo (55 ± 18 pM) observed throughout the water column, but low dFe concentrations (0.29 ± 0.08 nM). Given that annual dust supply is an order of magnitude greater in the North than the South Atlantic, the dCo distribution was somewhat unexpected. However, the distribution of dCo shows similarities with the distribution of phosphate (PO43−) in the euphotic zone of the Atlantic Ocean, where the North Atlantic gyre is characterised by chronically low PO4, and higher concentrations are observed in the South Atlantic gyre (Mather et al., 2008), suggesting the potential for a similar biological control of dCo distributions. Inverse correlations between dCo and Prochlorococcus abundance in the North Atlantic gyre provinces, combined with extremely low dCo where nitrogen fixation rates were highest (∼20–28°N), suggests the dominance of biological controls on dCo distributions. The contrasting dCo and dFe distributions in the North and South Atlantic gyres provides insights into the differences between the dominant controls on the distribution of these two bioactive trace metals in the central Atlantic Ocean.

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Accepted/In Press date: 10 November 2016
e-pub ahead of print date: 27 November 2016
Published date: 1 November 2017
Organisations: Marine Biogeochemistry

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Local EPrints ID: 406497
URI: https://eprints.soton.ac.uk/id/eprint/406497
ISSN: 0079-6611
PURE UUID: 9da21600-0e32-44c7-94d2-a0509a040b3f
ORCID for Neil J. Wyatt: ORCID iD orcid.org/0000-0002-1080-7778

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Date deposited: 18 Mar 2017 02:20
Last modified: 03 Dec 2019 06:14

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