The possible occurrence of iron-dependent anaerobic methane oxidation in an Archean Ocean analogue.

ABSTRACT: In the ferruginous and anoxic early Earth oceans, photoferrotrophy drove most of the biological production before the advent of oxygenic photosynthesis, but its association with ferric iron (Fe³⁺) dependent anaerobic methane (CH₄) oxidation (AOM) has been poorly investigated. We studied AOM in Kabuno Bay, a modern analogue to the Archean Ocean (anoxic bottom waters and dissolved Fe concentrations >?600 µmol L^-1). Aerobic and anaerobic CH₄ oxidation rates up to 0.12?±?0.03 and 51?±?1 µmol L^-1 d^-1, respectively, were put in evidence. In the Fe oxidation-reduction zone, we observed high concentration of Bacteriochlorophyll e (biomarker of the anoxygenic photoautotrophs), which co-occurred with the maximum CH₄ oxidation peaks, and a high abundance of Candidatus Methanoperedens, which can couple AOM to Fe³⁺ reduction. In addition, comparison of measured CH₄ oxidation rates with electron acceptor fluxes suggest that AOM could mainly rely on Fe³⁺ produced by photoferrotrophs. Further experiments specifically targeted to investigate the interactions between photoferrotrophs and AOM would be of considerable interest. Indeed, ferric Fe³⁺-driven AOM has been poorly envisaged as a possible metabolic process in the Archean ocean, but this can potentially change the conceptualization and modelling of metabolic and geochemical processes controlling climate conditions in the Early Earth.

SUBMITTER: Roland FAE 

PROVIDER: S-EPMC7810693 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature