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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-21
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-21
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 31 Jan 2019

Research article | 31 Jan 2019

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This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Evidence for microbial iron reduction in the methanogenic sediments of the oligotrophic SE Mediterranean continental shelf

Hanni Vigderovich1, Lewen Liang2, Barak Herut3, Fengping Wang2, Eyal Wurgaft1,a, Maxim Rubin-Blum3, and Orit Sivan1 Hanni Vigderovich et al.
  • 1The Department of Geological and Environmental Sciences, Ben-Gurion University of the Negev, Beer-Sheva, 8410501, Israel
  • 2School of Life Sciences and Biotechnology, Shanghai JiaoTong University, Shanghai, 200240, China
  • 3Israel Oceanographic and Limnological Research, Haifa, 31080, Israel
  • acurrently at: The Department of Marine Chemistry and Biochemistry, Woods-Hole Oceanographic Institution, Woods-Hole, USA

Abstract. Dissimilatory iron reduction is probably one of the earliest metabolisms, which still participates in important biogeochemical cycles such as carbon and sulfur. Traditionally, this process is thought to be limited to the shallow part of the sediment column, as one of the energetically favorable anaerobic microbial respiration cascade, usually coupled to the oxidation of organic matter. However, in the last decade iron reduction has been observed in the methanogenic depth in many aquatic sediments, suggesting a link between the iron and the methane cycles. Yet, the mechanistic nature of this link has yet to be established, and has not been studied in oligotrophic shallow marine sediments. In this study we present first geochemical and molecular evidences for microbial iron reduction in the methanogenic depth of the oligotrophic Southern Eastern (SE) Mediterranean continental shelf. Geochemical pore-water profiles indicate iron reduction in two zones, the traditional zone in the upper part of the sediment cores and a deeper second zone located in the enhanced methane concentration layer. Results from a slurry incubation experiment indicate that the iron reduction is microbial. The Geochemical data, Spearman correlation between microbial abundance and iron concentration, as well as the qPCR analysis of the mcrA gene point to several potential microorganisms that could be involved in this iron reduction via three potential pathways: H2/organic matter oxidation, an active sulfur cycle or iron driven anaerobic oxidation of methane.

Hanni Vigderovich et al.
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Hanni Vigderovich et al.
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Short summary
Microbial iron reduction participates in important biogeochemical cycles. In the last decade iron reduction has been observed in many aquatic sediments below its classical zone, in the methane production zone, suggesting a link between the two cycles. Here we present evidence for microbial iron reduction in the methanogenic depth of the oligotrophic SE Mediterranean continental shelf using mainly geochemical and microbial sedimentary profiles and suggest possible mechanisms for this process.
Microbial iron reduction participates in important biogeochemical cycles. In the last decade...
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