The Methane Cycle in Ferruginous Lake Matano

The Methane Cycle in Ferruginous Lake Matano

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  • November 20, 2018
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In Lake Matano, Indonesia, the world’s largest known ferruginous basin, more than 50% of authigenic organic matter is degraded through methanogenesis, despite high abundances of Fe (hydr) oxides in the lake sediments. Biogenic CH 4 accumulates to high concentrations (up to 1.4 mmol L− 1) in the anoxic bottom waters, which contain a total of 7.4× 10 5 tons of CH 4. Profiles of dissolved inorganic carbon (ΣCO 2) and carbon isotopes (δ 13 C) show that CH 4 is oxidized in the vicinity of the persistent pycnocline and that some of this CH 4 is likely oxidized anaerobically. The dearth of NO 3− and SO 4 2− in Lake Matano waters suggests that anaerobic methane oxidation may be coupled to the reduction of Fe (and/or Mn)(hydr) oxides. Thermodynamic considerations reveal that CH 4 oxidation coupled to Fe (III) or Mn (III/IV) reduction would yield sufficient free energy to support microbial growth at the substrate …

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