title: High rates of anaerobic methanotrophy at low sulfate concentrations with implications for past and present methane levels.
abstract: Despite the importance of the anaerobic oxidation of methane (AOM) to global biogeochemical cycles, the relationship between sulfate concentration and the rate of AOM has not been previously experimentally constrained. Here, we present measurements showing substantial methane oxidation at low sulfate concentrations, with no significant decrease in the rate of AOM until sulfate levels are well below 1 mM. At sulfate levels below 1 mM, there appears to be a strong decoupling of AOM and sulfate reduction, with a (13)C-label transferred from methane to carbon dioxide occurring at a rate almost an order of magnitude faster than the observed rate of sulfate reduction. These results allow for the possibility that high rates of AOM occurred in the Archean oceans and that high rates of AOM may be found in freshwater environments (lakes, rivers, etc.) and deep ocean sediments today.
authors.affiliation: Department of Geosciences, The Pennsylvania State University, University Park, PA, USA. ejbeal@gmail.com
authors.forename: E J
authors.initials: EJ
authors.lastname: Beal
authors.forename: M W
authors.initials: MW
authors.lastname: Claire
authors.forename: C H
authors.initials: CH
authors.lastname: House
mesh_terms: D000693:Anaerobiosis; D001105:Archaea / Q000378:metabolism*; D001419:Bacteria / Q000378:metabolism*; D002140:California; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes / Q000378:metabolism; D005618:Fresh Water; D019015:Geologic Sediments; D008697:Methane / Q000378:metabolism*; D010084:Oxidation-Reduction; D010140:Pacific Ocean; D010163:Paleontology; D013431:Sulfates / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D013431:Sulfates; D002245:Carbon Dioxide; D008697:Methane