title: Biological formation of ethane and propane in the deep marine subsurface.
abstract: Concentrations and isotopic compositions of ethane and propane in cold, deeply buried sediments from the southeastern Pacific are best explained by microbial production of these gases in situ. Reduction of acetate to ethane provides one feasible mechanism. Propane is enriched in (13)C relative to ethane. The amount is consistent with derivation of the third C from inorganic carbon dissolved in sedimentary pore waters. At typical sedimentary conditions, the reactions yield free energy sufficient for growth. Relationships with competing processes are governed mainly by the abundance of H(2). Production of C(2) and C(3) hydrocarbons in this way provides a sink for acetate and hydrogen but upsets the general belief that hydrocarbons larger than methane derive only from thermal degradation of fossil organic material.
authors.affiliation: Deutsche Forschungsgemeinschaft-Research Center Ocean Margins, Department of Geosciences, University of Bremen, P.O. Box 330440, 28334 Bremen, Germany. khinrichs@uni-bremen.de
authors.forename: Kai-Uwe
authors.initials: KU
authors.lastname: Hinrichs
authors.forename: John M
authors.initials: JM
authors.lastname: Hayes
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bach
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Spivack
authors.forename: Laura R
authors.initials: LR
authors.lastname: Hmelo
authors.forename: Nils G
authors.initials: NG
authors.lastname: Holm
authors.forename: Carl G
authors.initials: CG
authors.lastname: Johnson
authors.forename: Sean P
authors.initials: SP
authors.lastname: Sylva
mesh_terms: D002247:Carbon Isotopes; D004980:Ethane / Q000032:analysis*; D019015:Geologic Sediments / Q000737:chemistry; D011407:Propane / Q000032:analysis*; D012623:Seawater / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D002247:Carbon Isotopes; D004980:Ethane; D011407:Propane