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Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/7169

Authors: Roberts, A. P.*
Florindo, F.*
Villa, G.*
Chang, L.*
Jovane, L.*
Bohaty, S. M.*
Larrasoaña, J. C.*
Heslop, D.*
Fitz Gerald, J. D.*
Title: Magnetotactic bacterial abundance in pelagic marine environments is limited by organic carbon flux and availability of dissolved iron
Title of journal: Earth and Planetary Science Letters
Series/Report no.: 3-4/310 (2011)
Publisher: Elsevier B.V.
Issue Date: 15-Oct-2011
DOI: 10.1016/j.epsl.2011.08.011
Keywords: Magnetotactic bacteria
Magnetofossils
Magnetite
Productivity
Iron
Organic carbon
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 ironbearing 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.
Appears in Collections:04.05.09. Environmental magnetism
04.05.07. Rock magnetism
04.05.06. Paleomagnetism
Papers Published / Papers in press

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