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

journal contribution
posted on 2023-05-18, 17:29 authored by Ellwood, MJ, Hutchins, DA, Lohan, MC, Milne, A, Nasemann, P, Nodder, SD, Sander, SG, Robert StrzepekRobert Strzepek, Wilhelm, SW, Philip BoydPhilip Boyd
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.


Publication title

Proceedings of the National Academy of Sciences of the United States of America








Institute for Marine and Antarctic Studies


Natl Acad Sciences

Place of publication

2101 Constitution Ave Nw, Washington, USA, Dc, 20418

Rights statement

Copyright 2014 The Authors

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  • Restricted

Socio-economic Objectives

Measurement and assessment of marine water quality and condition

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