A Critical Look at the Combined Use of Sulfur and Oxygen Isotopes to Study Microbial Metabolisms in Methane-Rich Environments

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  • Gilad Antler, Univ Cambridge, University of Cambridge, Dept Earth Sci, Ben Gurion Univ Negev, Ben Gurion University, Dept Geol & Environm Sci, Interuniv Inst Marine Sci, H Steinitz Marine Biol Lab
  • ,
  • Andre Pellerin

Separating the contributions of anaerobic oxidation of methane and organoclastic sulfate reduction in the overall sedimentary sulfur cycle of marine sediments has benefited from advances in isotope biogeochemistry. Particularly, the coupling of sulfur and oxygen isotopes measured in the residual sulfate pool (delta O-18(SO4) vs. delta S-34(SO4)). Yet, some important questions remain. Recent works have observed patterns that are inconsistent with previous interpretations. We differentiate the contributions of oxygen and sulfur isotopes to separating the anaerobic oxidation of methane and organoclastic sulfate reduction into three phases; first evidence from conventional high methane vs. low methane sites suggests a clear relationship between oxygen and sulfur isotopes in porewater and the metabolic process taking place. Second, evidence from pure cultures and organic matter rich sites with low levels of methane suggest the signatures of both processes overlap and cannot be differentiated. Third, we take a critical look at the use of oxygen and sulfur isotopes to differentiate metabolic processes (anaerobic oxidation of methane vs. organoclastic sulfate reduction). We identify that it is essential to develop a better understanding of the oxygen kinetic isotope effect, the degree of isotope exchange with sulfur intermediates as well as establishing their relationships with the cell-specific metabolic rates if we are to develop this proxy into a reliable tool to study the sulfur cycle in marine sediments and the geological record.

Original languageEnglish
Article number519
JournalFrontiers in Microbiology
Volume9
Number of pages7
ISSN1664-302X
DOIs
Publication statusPublished - 6 Apr 2018

    Research areas

  • sulfur isotopes, oxygen isotopes, anaerobic oxidation of methane (AOM), sulfate reduction rates, marine sediments, DISSIMILATORY SULFATE REDUCTION, ANAEROBIC OXIDATION, BIOGENIC METHANE, DEEP BIOSPHERE, STABLE SULFUR, PORE FLUID, BALTIC SEA, SEDIMENTS, FRACTIONATION, MARINE

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