title: Global rates of marine sulfate reduction and implications for sub-sea-floor metabolic activities.
abstract: Sulfate reduction is a globally important redox process in marine sediments, yet global rates are poorly quantified. We developed an artificial neural network trained with 199 sulfate profiles, constrained with geomorphological and geochemical maps to estimate global sulfate-reduction rate distributions. Globally, 11.3 teramoles of sulfate are reduced yearly (~15% of previous estimates), accounting for the oxidation of 12 to 29% of the organic carbon flux to the sea floor. Combined with global cell distributions in marine sediments, these results indicate a strong contrast in sub-sea-floor prokaryote habitats: In continental margins, global cell numbers in sulfate-depleted sediment exceed those in the overlying sulfate-bearing sediment by one order of magnitude, whereas in the abyss, most life occurs in oxic and/or sulfate-reducing sediments.
authors.affiliation: MARUM Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany. bowlesmw@uni-bremen.de.
authors.forename: Marshall W
authors.initials: MW
authors.lastname: Bowles
authors.affiliation: MARUM Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany. Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany. Department of Earth Sciences-Geochemistry, Faculty of Geosciences, Utrecht University, Netherlands.
authors.forename: José M
authors.initials: JM
authors.lastname: Mogollón
authors.affiliation: MARUM Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany. Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Kasten
authors.affiliation: MARUM Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Zabel
authors.affiliation: MARUM Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany.
authors.forename: Kai-Uwe
authors.initials: KU
authors.lastname: Hinrichs
mesh_terms: D002244:Carbon / Q000378:metabolism*; D017753:Ecosystem; D019015:Geologic Sediments / Q000382:microbiology*; D016571:Neural Networks, Computer; D010084:Oxidation-Reduction; D012623:Seawater / Q000382:microbiology*; D013431:Sulfates / Q000378:metabolism*
chemical_list: D013431:Sulfates; D002244:Carbon