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Uniquely low stable iron isotopic signatures in deep marine sediments caused by Rayleigh distillation.

ABSTRACT: Dissimilatory iron reduction (DIR) is suggested to be one of the earliest forms of microbial respiration. It plays an important role in the biogeochemical cycling of iron in modern and ancient sediments. Since microbial iron cycling is typically accompanied by iron isotope fractionation, stable iron isotopes are used as tracer for biological activity. Here we present iron isotope data for dissolved and sequentially extracted sedimentary iron pools from deep and hot subseafloor sediments retrieved in the Nankai Trough off Japan. Dissolved iron (Fe(II)_aq) is isotopically light throughout the ferruginous sediment interval but some samples have exceptionally light isotope values. Such light values have never been reported in natural marine environments and cannot be solely attributed to DIR. We show that the light isotope values are best explained by a Rayleigh distillation model where Fe(II)_aq is continuously removed from the pore water by adsorption onto iron (oxyhydr)oxide surfaces. While the microbially mediated Fe(II)_aq release has ceased due to an increase in temperature beyond the threshold of mesophilic microorganisms, the abiotic adsorptive Fe(II)_aq removal continued, leading to uniquely light isotope values. These findings have important implications for the interpretation of dissolved iron isotope data especially in deep subseafloor sediments.

SUBMITTER: Koster M

PROVIDER: S-EPMC10290645 | biostudies-literature | 2023 Jun

REPOSITORIES: biostudies-literature

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Uniquely low stable iron isotopic signatures in deep marine sediments caused by Rayleigh distillation.

Köster Male M Staubwasser Michael M Meixner Anette A Kasemann Simone A SA Manners Hayley R HR Morono Yuki Y Inagaki Fumio F Heuer Verena B VB Kasten Sabine S Henkel Susann S

Scientific reports 20230624 1

Dissimilatory iron reduction (DIR) is suggested to be one of the earliest forms of microbial respiration. It plays an important role in the biogeochemical cycling of iron in modern and ancient sediments. Since microbial iron cycling is typically accompanied by iron isotope fractionation, stable iron isotopes are used as tracer for biological activity. Here we present iron isotope data for dissolved and sequentially extracted sedimentary iron pools from deep and hot subseafloor sediments retrieve ...[more]

PMID: 37355766

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Uniquely low stable iron isotopic signatures in deep marine sediments caused by Rayleigh distillation.

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Uniquely low stable iron isotopic signatures in deep marine sediments caused by Rayleigh distillation.

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