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Sulfide Oxidation across Diffuse Flow Zones of Hydrothermal Vents |
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| Authors: | Amy Gartman Mustafa Y��cel Andrew S. Madison David W. Chu Shufen Ma Christopher P. Janzen Erin L. Becker Roxanne A. Beinart Peter R. Girguis George W. Luther III |
| Affiliation: | 1. School of Marine Science and Policy, College of Earth, Ocean and Environment, University of Delaware, Lewes, DE, 19958, USA 7. Laboratory of Benthic Ecogeochemistry (LECOB), Observatoire Oceanologique de Banyuls, Universit?? Pierre et Marie Curie??Paris 6, 66651, Banyuls-sur-mer, France 2. Department of Chemistry and Biochemistry, School of Marine Science and Policy, College of Earth, Ocean and Environment, University of Delaware, Lewes, DE, 19958, USA 6. Department of Earth and Planetary Science, University of California, Berkeley, CA, 94720, USA 3. Department of Chemistry, Susquehanna University, Selinsgrove, PA, 17870, USA 4. Biology Department, Penn State University, University Park, PA, 16801, USA 5. Department of Organismic & Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA |
| Abstract: | The sulfide (H2S/HS?) that is emitted from hydrothermal vents begins to oxidize abiotically with oxygen upon contact with ambient bottom water, but the reaction kinetics are slow. Here, using in situ voltammetry, we report detection of the intermediate sulfur oxidation products polysulfides [ $ {text{S}}_{text{x}}^{2 - } $ ] and thiosulfate [ $ {text{S}}_{ 2} {text{O}}_{ 3}^{ 2- } $ ], along with contextual data on sulfide, oxygen, and temperature. At Lau Basin in 2006, thiosulfate was identified in less than one percent of approximately 10,500 scans and no polysulfides were detected. Only five percent of 11,000 voltammetric scans taken at four vent sites at Lau Basin in May 2009 show either thiosulfate or polysulfides. These in situ data indicate that abiotic sulfide oxidation does not readily occur as H2S contacts oxic bottom waters. Calculated abiotic potential sulfide oxidation rates are <10?3 ??M/min and are consistent with slow oxidation and the observed lack of sulfur oxidation intermediates. It is known that the thermodynamics for the first electron transfer step for sulfide and oxygen during sulfide oxidation in these systems are unfavorable, and that the kinetics for two electron transfers are not rapid. Here, we suggest that different metal catalyzed and/or biotic reaction pathways can readily produce sulfur oxidation intermediates. Via shipboard high-pressure incubation experiments, we show that snails with chemosynthetic endosymbionts do release polysulfides and may be responsible for our field observations of polysulfides. |
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