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

• Published in: Earth and Planetary Science Letters
• Main Authors: Roberts, A. P., Florindo, F., Villa, G., Chang, L., Jovane, L., Bohaty, S. M., Larrasoaña, J. C., Heslop, D., Fitz Gerald, J. D.
• Other Authors: Roberts, A. P.; National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK, Florindo, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia, Villa, G.; Dipartimento Scienze della Terra, Università di Parma, Viale Usberti 157A, 43100 Parma, Italy, Chang, L.; National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK, Jovane, L.; National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK, Bohaty, S. M.; National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK, Larrasoaña, J. C.; Área de Cambio Global, IGME, Oficina de Proyectos de Zaragoza, Manuel Lasala 44 9B, Zaragoza 50006, Spain, Heslop, D.; Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia, Fitz Gerald, J. D.; Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia, National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK, Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia, Dipartimento Scienze della Terra, Università di Parma, Viale Usberti 157A, 43100 Parma, Italy, Área de Cambio Global, IGME, Oficina de Proyectos de Zaragoza, Manuel Lasala 44 9B, Zaragoza 50006, Spain, Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier B.V. 2011
• Subjects: Magnetotactic bacteria; Magnetofossils; Magnetite; Productivity; Iron; Organic carbon; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism; 04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism; 04. Solid Earth::04.05. Geomagnetism::04.05.09. Environmental magnetism; Kerguelen; Southern Ocean; Arctic
• Online Access: http://hdl.handle.net/2122/7169; https://doi.org/10.1016/j.epsl.2011.08.011

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. Published 441-452 1.8. Osservazioni di geofisica ambientale 2.2. Laboratorio di paleomagnetismo JCR Journal restricted