Distinct iron cycling in a Southern Ocean eddy

Michael J. Ellwood*, Robert F. Strzepek, Peter G. Strutton, Thomas W. Trull, Marion Fourquez, Philip W. Boyd

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    53 Citations (Scopus)


    Mesoscale eddies are ubiquitous in the iron-limited Southern Ocean, controlling ocean-atmosphere exchange processes, however their influence on phytoplankton productivity remains unknown. Here we probed the biogeochemical cycling of iron (Fe) in a cold-core eddy. In-eddy surface dissolved Fe (dFe) concentrations and phytoplankton productivity were exceedingly low relative to external waters. In-eddy phytoplankton Fe-to-carbon uptake ratios were elevated 2–6 fold, indicating upregulated intracellular Fe acquisition resulting in a dFe residence time of ~1 day. Heavy dFe isotope values were measured for in-eddy surface waters highlighting extensive trafficking of dFe by cells. Below the euphotic zone, dFe isotope values were lighter and coincident with peaks in recycled nutrients and cell abundance, indicating enhanced microbially-mediated Fe recycling. Our measurements show that the isolated nature of Southern Ocean eddies can produce distinctly different Fe biogeochemistry compared to surrounding waters with cells upregulating iron uptake and using recycling processes to sustain themselves.

    Original languageEnglish
    Article number825
    JournalNature Communications
    Issue number1
    Publication statusPublished - 1 Dec 2020


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