Magnetotactic bacterial abundance in pelagic marine environments is limited by organic carbon flux and availability of dissolved iron

Andrew P. Roberts*, Fabio Florindo, Giuliana Villa, Liao Chang, Luigi Jovane, Steven M. Bohaty, Juan C. Larrasoaña, David Heslop, John D. Fitz Gerald

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    153 Citations (Scopus)

    Abstract

    Magnetotactic bacteria intracellularly biomineralize magnetite of an ideal grain size for recording palaeomagnetic signals. However, bacterial magnetite has only been reported in a few pre-Quaternary records because progressive burial into anoxic diagenetic environments causes its dissolution. Deep-sea carbonate sequences provide optimal environments for preserving bacterial magnetite due to low rates of organic carbon burial and expanded pore-water redox zonations. Such sequences often do not become anoxic for tens to hundreds of metres below the seafloor. Nevertheless, the biogeochemical factors that control magnetotactic bacterial populations in such settings are not well known. We document the preservation of bacterial magnetite, which dominates the palaeomagnetic signal throughout Eocene pelagic carbonates from the southern Kerguelen Plateau, Southern Ocean. We provide evidence that iron fertilization, associated with increased aeolian dust flux, resulted in surface water eutrophication in the late Eocene that controlled bacterial magnetite abundance via export of organic carbon to the seafloor. Increased flux of aeolian iron-bearing phases also delivered iron to the seafloor, some of which became bioavailable through iron reduction. Our results suggest that magnetotactic bacterial populations in pelagic settings depend crucially on particulate iron and organic carbon delivery to the seafloor.

    Original languageEnglish
    Pages (from-to)441-452
    Number of pages12
    JournalEarth and Planetary Science Letters
    Volume310
    Issue number3-4
    DOIs
    Publication statusPublished - 15 Oct 2011

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