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Iron stable isotopes track pelagic iron cycling during a subtropical phytoplankton bloom

Iron stable isotopes track pelagic iron cycling during a subtropical phytoplankton bloom
Iron stable isotopes track pelagic iron cycling during a subtropical phytoplankton bloom
The supply and bioavailability of dissolved iron sets the magnitude of surface productivity for ∼40% of the global ocean. The redox state, organic complexation, and phase (dissolved versus particulate) of iron are key determinants of iron bioavailability in the marine realm, although the mechanisms facilitating exchange between iron species (inorganic and organic) and phases are poorly constrained. Here we use the isotope fingerprint of dissolved and particulate iron to reveal distinct isotopic signatures for biological uptake of iron during a GEOTRACES process study focused on a temperate spring phytoplankton bloom in subtropical waters. At the onset of the bloom, dissolved iron within the mixed layer was isotopically light relative to particulate iron. The isotopically light dissolved iron pool likely results from the reduction of particulate iron via photochemical and (to a lesser extent) biologically mediated reduction processes. As the bloom develops, dissolved iron within the surface mixed layer becomes isotopically heavy, reflecting the dominance of biological processing of iron as it is removed from solution, while scavenging appears to play a minor role. As stable isotopes have shown for major elements like nitrogen, iron isotopes offer a new window into our understanding of the biogeochemical cycling of iron, thereby allowing us to disentangle a suite of concurrent biotic and abiotic transformations of this key biolimiting element.
0027-8424
E15-E20
Ellwood, Michael J.
fa04ddcb-ab30-4973-beba-3da302baa300
Hutchins, David A.
22662c12-8eb0-4279-8217-a6313f2c528e
Lohan, Maeve C.
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Milne, Angela
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Nasemann, Philipp
850bba25-0de8-407a-b794-2810a52e0015
Nodder, Scott D.
52b35ad3-7760-4fbf-915c-5ce456315a29
Sander, Sylvia G.
7e8fbb87-c8de-4a85-a490-b789a35e8134
Strzepek, Robert
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Wilhelm, Steven W.
b90654c9-6378-4bd1-ab4f-0b1a1f4aa8fc
Boyd, Philip W.
af169f41-8873-4ad8-bd70-579c291dc00d
Ellwood, Michael J.
fa04ddcb-ab30-4973-beba-3da302baa300
Hutchins, David A.
22662c12-8eb0-4279-8217-a6313f2c528e
Lohan, Maeve C.
6ca10597-2d0f-40e8-8e4f-7619dfac5088
Milne, Angela
39b44fbd-8f5e-40ea-80c9-244c20998020
Nasemann, Philipp
850bba25-0de8-407a-b794-2810a52e0015
Nodder, Scott D.
52b35ad3-7760-4fbf-915c-5ce456315a29
Sander, Sylvia G.
7e8fbb87-c8de-4a85-a490-b789a35e8134
Strzepek, Robert
7828ea13-a164-4b0b-8cc1-2a572cdf4b8f
Wilhelm, Steven W.
b90654c9-6378-4bd1-ab4f-0b1a1f4aa8fc
Boyd, Philip W.
af169f41-8873-4ad8-bd70-579c291dc00d

Ellwood, Michael J., Hutchins, David A., Lohan, Maeve C., Milne, Angela, Nasemann, Philipp, Nodder, Scott D., Sander, Sylvia G., Strzepek, Robert, Wilhelm, Steven W. and Boyd, Philip W. (2015) Iron stable isotopes track pelagic iron cycling during a subtropical phytoplankton bloom. Proceedings of the National Academy of Sciences of the United States of America, 112 (1), E15-E20. (doi:10.1073/pnas.1421576112).

Record type: Article

Abstract

The supply and bioavailability of dissolved iron sets the magnitude of surface productivity for ∼40% of the global ocean. The redox state, organic complexation, and phase (dissolved versus particulate) of iron are key determinants of iron bioavailability in the marine realm, although the mechanisms facilitating exchange between iron species (inorganic and organic) and phases are poorly constrained. Here we use the isotope fingerprint of dissolved and particulate iron to reveal distinct isotopic signatures for biological uptake of iron during a GEOTRACES process study focused on a temperate spring phytoplankton bloom in subtropical waters. At the onset of the bloom, dissolved iron within the mixed layer was isotopically light relative to particulate iron. The isotopically light dissolved iron pool likely results from the reduction of particulate iron via photochemical and (to a lesser extent) biologically mediated reduction processes. As the bloom develops, dissolved iron within the surface mixed layer becomes isotopically heavy, reflecting the dominance of biological processing of iron as it is removed from solution, while scavenging appears to play a minor role. As stable isotopes have shown for major elements like nitrogen, iron isotopes offer a new window into our understanding of the biogeochemical cycling of iron, thereby allowing us to disentangle a suite of concurrent biotic and abiotic transformations of this key biolimiting element.

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More information

e-pub ahead of print date: 22 December 2014
Published date: 6 January 2015
Organisations: Ocean and Earth Science, Marine Biogeochemistry

Identifiers

Local EPrints ID: 406493
URI: http://eprints.soton.ac.uk/id/eprint/406493
ISSN: 0027-8424
PURE UUID: f4357018-6fc1-4a35-a027-8f3bc1531933
ORCID for Maeve C. Lohan: ORCID iD orcid.org/0000-0002-5340-3108

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Date deposited: 18 Mar 2017 02:20
Last modified: 09 Jan 2022 03:42

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Contributors

Author: Michael J. Ellwood
Author: David A. Hutchins
Author: Maeve C. Lohan ORCID iD
Author: Angela Milne
Author: Philipp Nasemann
Author: Scott D. Nodder
Author: Sylvia G. Sander
Author: Robert Strzepek
Author: Steven W. Wilhelm
Author: Philip W. Boyd

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