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The methane cycle in ferruginous Lake Matano
Author(s) -
CROWE S. A.,
KATSEV S.,
LESLIE K.,
STURM A.,
MAGEN C.,
NOMOSATRYO S.,
PACK M. A.,
KESSLER J. D.,
REEBURGH W. S.,
ROBERTS J. A.,
GONZÁLEZ L.,
DOUGLAS HAFFNER G.,
MUCCI A.,
SUNDBY B.,
FOWLE D. A.
Publication year - 2011
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/j.1472-4669.2010.00257.x
Subject(s) - methanogenesis , anoxic waters , methane , authigenic , environmental chemistry , water column , anaerobic oxidation of methane , chemistry , biogeochemical cycle , euryarchaeota , acetogenesis , archaea , organic matter , geochemistry , geology , oceanography , paleontology , bacteria , organic chemistry , diagenesis
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 levels present in Lake Matano. Flux calculations imply that Fe and Mn must be recycled several times directly within the water column to balance the upward flux of CH 4 . 16S gene cloning identified methanogens in the anoxic water column, and these methanogens belong to groups capable of both acetoclastic and hydrogenotrophic methanogenesis. We find that methane is important in C cycling, even in this very Fe‐rich environment. Such Fe‐rich environments are rare on Earth today, but they are analogous to conditions in the ferruginous oceans thought to prevail during much of the Archean Eon. By analogy, methanogens and methanotrophs could have formed an important part of the Archean Ocean ecosystem.