The University of Southampton
University of Southampton Institutional Repository

Physical and biogeochemical controls on seasonal iron, manganese, and cobalt distributions in Northeast Atlantic shelf seas

Physical and biogeochemical controls on seasonal iron, manganese, and cobalt distributions in Northeast Atlantic shelf seas
Physical and biogeochemical controls on seasonal iron, manganese, and cobalt distributions in Northeast Atlantic shelf seas
Dissolved (<0.2 μm) trace metals (dTMs) including iron (Fe), manganese (Mn), and cobalt (Co) are micronutrients that (co-) limit phytoplankton growth in many ocean regions. Here, we present the spatial and seasonal distributions of dFe, dMn, and dCo on the Northeast Atlantic continental margin (Celtic Sea), along a transect across the shelf and two off-shelf transects along a canyon and a spur. Waters on the continental shelf showed much higher dTM concentrations (dFe 0.07–6.50 nmol L−1, average 1.41 ± 0.96 nmol L−1, n = 138; dMn 0.868–14.8 nmol L−1, 2.75 ± 2.37 nmol L−1, n = 148; dCo 54.8–217 pmol L−1, 109 ± 32 pmol L−1, n = 144) than on the slope (dFe 0.03–1.90 nmol L−1, 0.65 ± 0.43 nmol L−1, n = 454; dMn 0.223–1.14 nmol L−1, 0.58 ± 0.20 nmol L−1, n = 458; dCo 27.3–122 pmol L−1, 71.7 ± 11.7 pmol L−1, n = 441), attributed to strong dTM contributions from a low-salinity endmember, i.e., riverine discharge. Benthic sedimentary input via reductive dissolution (especially for dFe and dMn), delineated by short-lived radium (Ra) isotopic activities (223Raxs and 224Raxs), was only prominent at a station (Site A) characterized by fine sediments. On the continental slope, dMn levels at depth were mainly determined by the formation of insoluble Mn oxides and the intrusion of Mediterranean Outflow Waters. In contrast, dFe and dCo concentrations at depth were balanced by the regeneration from remineralization of sinking organic particles and scavenging removal. In addition, bottom and intermediate nepheloid layers along the slope illustrated both elevated dTM concentrations and Ra isotopic activities. The presence of nepheloid layers is especially significant along the canyon transect relative to the spur transect, demonstrating the importance of slope topography on the off-shelf transport of dTMs into the Northeast Atlantic Ocean.

As a seasonal stratified shelf sea, dTMs and nutrients showed synchronized seasonal variations on the shelf, indicating the influence of biological processes in addition to source effects. Surface dFe and dCo were depleted in summer due to enhanced biological uptake, while sub-surface dFe and dCo were elevated in summer and autumn ascribed to the remineralization of sinking organic particles. In contrast, surface dMn levels were predominantly controlled by the seasonal variations in photoreduction, while sub-surface dMn concentrations were relatively constant throughout the year. The combined effects of fluvial and benthic sources, topographical controls, and biological processes shape the seasonal variations of dTM distributions. Such seasonal variations in dTMs and biological activities can affect the biological carbon pump on the Northeast Atlantic continental margin, and may further influence the carbon cycle in the Atlantic Ocean via the dynamic dTM exchange between continental margins and the open ocean.
Dissolved trace metals, North Atlantic, Radium isotopes, Remineralization, Seasonal variation
0016-7037
278-295
Chen, Xue-Gang
2e730f49-f4b2-409f-a8b0-ad892d2ceb10
Rusiecka, Dagmara
70c9f91b-6ed5-451a-bccb-832fb7022724
Gledhill, Martha
da795c1e-1489-4d40-9df1-fc6bde54382d
Milne, Angela
39b44fbd-8f5e-40ea-80c9-244c20998020
Annett, Amber
de404d72-7e90-4dbd-884a-1df813808276
Beck, Aaron Joseph
cadd6a98-162b-4cf4-9407-18c9dd045682
Birchill, A.J.
d369bd78-52d0-4770-ab67-37137bc3da2b
Lohan, Maeve C.
6ca10597-2d0f-40e8-8e4f-7619dfac5088
Ussher, Simon
ac1386f0-f0a1-4663-8fc5-26dbc178327b
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Chen, Xue-Gang
2e730f49-f4b2-409f-a8b0-ad892d2ceb10
Rusiecka, Dagmara
70c9f91b-6ed5-451a-bccb-832fb7022724
Gledhill, Martha
da795c1e-1489-4d40-9df1-fc6bde54382d
Milne, Angela
39b44fbd-8f5e-40ea-80c9-244c20998020
Annett, Amber
de404d72-7e90-4dbd-884a-1df813808276
Beck, Aaron Joseph
cadd6a98-162b-4cf4-9407-18c9dd045682
Birchill, A.J.
d369bd78-52d0-4770-ab67-37137bc3da2b
Lohan, Maeve C.
6ca10597-2d0f-40e8-8e4f-7619dfac5088
Ussher, Simon
ac1386f0-f0a1-4663-8fc5-26dbc178327b
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9

Chen, Xue-Gang, Rusiecka, Dagmara, Gledhill, Martha, Milne, Angela, Annett, Amber, Beck, Aaron Joseph, Birchill, A.J., Lohan, Maeve C., Ussher, Simon and Achterberg, Eric P. (2023) Physical and biogeochemical controls on seasonal iron, manganese, and cobalt distributions in Northeast Atlantic shelf seas. Geochimica et Cosmochimica Acta, 348, 278-295. (doi:10.1016/j.gca.2023.03.023).

Record type: Article

Abstract

Dissolved (<0.2 μm) trace metals (dTMs) including iron (Fe), manganese (Mn), and cobalt (Co) are micronutrients that (co-) limit phytoplankton growth in many ocean regions. Here, we present the spatial and seasonal distributions of dFe, dMn, and dCo on the Northeast Atlantic continental margin (Celtic Sea), along a transect across the shelf and two off-shelf transects along a canyon and a spur. Waters on the continental shelf showed much higher dTM concentrations (dFe 0.07–6.50 nmol L−1, average 1.41 ± 0.96 nmol L−1, n = 138; dMn 0.868–14.8 nmol L−1, 2.75 ± 2.37 nmol L−1, n = 148; dCo 54.8–217 pmol L−1, 109 ± 32 pmol L−1, n = 144) than on the slope (dFe 0.03–1.90 nmol L−1, 0.65 ± 0.43 nmol L−1, n = 454; dMn 0.223–1.14 nmol L−1, 0.58 ± 0.20 nmol L−1, n = 458; dCo 27.3–122 pmol L−1, 71.7 ± 11.7 pmol L−1, n = 441), attributed to strong dTM contributions from a low-salinity endmember, i.e., riverine discharge. Benthic sedimentary input via reductive dissolution (especially for dFe and dMn), delineated by short-lived radium (Ra) isotopic activities (223Raxs and 224Raxs), was only prominent at a station (Site A) characterized by fine sediments. On the continental slope, dMn levels at depth were mainly determined by the formation of insoluble Mn oxides and the intrusion of Mediterranean Outflow Waters. In contrast, dFe and dCo concentrations at depth were balanced by the regeneration from remineralization of sinking organic particles and scavenging removal. In addition, bottom and intermediate nepheloid layers along the slope illustrated both elevated dTM concentrations and Ra isotopic activities. The presence of nepheloid layers is especially significant along the canyon transect relative to the spur transect, demonstrating the importance of slope topography on the off-shelf transport of dTMs into the Northeast Atlantic Ocean.

As a seasonal stratified shelf sea, dTMs and nutrients showed synchronized seasonal variations on the shelf, indicating the influence of biological processes in addition to source effects. Surface dFe and dCo were depleted in summer due to enhanced biological uptake, while sub-surface dFe and dCo were elevated in summer and autumn ascribed to the remineralization of sinking organic particles. In contrast, surface dMn levels were predominantly controlled by the seasonal variations in photoreduction, while sub-surface dMn concentrations were relatively constant throughout the year. The combined effects of fluvial and benthic sources, topographical controls, and biological processes shape the seasonal variations of dTM distributions. Such seasonal variations in dTMs and biological activities can affect the biological carbon pump on the Northeast Atlantic continental margin, and may further influence the carbon cycle in the Atlantic Ocean via the dynamic dTM exchange between continental margins and the open ocean.

Text
Xue-Gang et al_shelf Seas_GCA - Accepted Manuscript
Download (11MB)

More information

Accepted/In Press date: 16 March 2023
e-pub ahead of print date: 21 March 2023
Published date: 1 May 2023
Additional Information: Funding Information: The authors thank the captain and crew of the RSS Discovery for their assistance during research expeditions and Malcolm Woodward and Carolyn Harrys for the macronutrient data. This project was funded by the UK Natural Environment Research Council (NE/K001973/1 (E. A. and M. G.), NE/K001779/1 (M. L.), NE/K002023/1 (A. A.), and NE/L501840/1 (A. B.)), and by GEOMAR. Publisher Copyright: © 2023 Elsevier Ltd
Keywords: Dissolved trace metals, North Atlantic, Radium isotopes, Remineralization, Seasonal variation

Identifiers

Local EPrints ID: 477219
URI: http://eprints.soton.ac.uk/id/eprint/477219
ISSN: 0016-7037
PURE UUID: 3324e247-448d-4af4-ad66-3b3da0e15cd9
ORCID for Amber Annett: ORCID iD orcid.org/0000-0002-3730-2438
ORCID for Maeve C. Lohan: ORCID iD orcid.org/0000-0002-5340-3108

Catalogue record

Date deposited: 01 Jun 2023 16:45
Last modified: 18 Mar 2024 05:31

Export record

Altmetrics

Contributors

Author: Xue-Gang Chen
Author: Dagmara Rusiecka
Author: Martha Gledhill
Author: Angela Milne
Author: Amber Annett ORCID iD
Author: Aaron Joseph Beck
Author: A.J. Birchill
Author: Maeve C. Lohan ORCID iD
Author: Simon Ussher

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×