Sivan, Orit and Adler, Michal and Pearson, Ann and Gelman, Faina and Bar-Or, Itay and John, Seth G. and Eckert, Werner (2011) Geochemical evidence for iron-mediated anaerobic oxidation of methane. Limnology and Oceanography, 56 (4). pp. 1536-1544. ISSN 0024-3590 http://resolver.caltech.edu/CaltechAUTHORS:20110929-130308222
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Anaerobic oxidation of methane (AOM) by sulfate has been recognized as a critical process to maintain this greenhouse gas stability by limiting methane flux to the atmosphere. We show geochemical evidence for AOM in deep lake sediments and demonstrate that AOM is likely driven by iron (Fe) reduction. Pore-water profiles from Lake Kinneret (Sea of Galilee, Israel) show that this sink for methane is located below the 20-cm depth in the sediment, which is well below the depths at which nitrate and sulfate are completely exhausted, as well as below the zone of methanogenesis. Iron-dependant AOM was verified by Fe(III)-amended mesocosm studies using intact sediment cores, and native iron oxides were detectable throughout the sediments. Because anaerobic Fe(III) respiration is thermodynamically more favorable than both sulfate-dependent methanotrophy and methanogenesis, its occurrence below the zone of methane production supports the idea that reduction of sedimentary iron oxides is kinetically or biologically limited. Similar conditions are likely to prevail in other incompletely pyritized aquatic sediments, indicating that AOM with Fe(III) is an important global sink for methane.
|Additional Information:||© 2011, by the American Society of Limnology and Oceanography, Inc. Received: 21 October 2010. Accepted: 22 March 2011. Amended: 13 May 2011. Associate editor: Mary I. Scranton. We thank Mina Bizic, E. Eliani, and G. Antler for their assistance in the field and the lab. We are grateful to our skippers, Moti Diamond and Meir Hatab, for their help in the field. We thank N. Teutsch and Y. Erel for their helpful suggestions for iron extraction and procedures and D. Johnston for helpful comments on the manuscript. Early discussions with D. Schrag on marine sediments were very helpful for this study. Special thanks go to the reviewers for their careful reviews and suggestions, which improved the manuscript. This research was funded partly by the Israel Ministry of National Infrastructures, Division of Research and Development, and partly by the Water Authority of Israel. O.S. and W.E. designed the research. M.A. performed most of the fieldwork, analyses, and one laboratory experiment together with O.S. and W.E. Two experiments were conducted by I.B. together with W.E.; O.S. and F.G. carried out the lipids extraction and its isotope analysis with the help of A.P.; and S.J. performed the iron isotope analyses. O.S. wrote the article with substantial contribution from A.P., and all authors discussed the results and commented on the manuscript.|
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|Deposited By:||Ruth Sustaita|
|Deposited On:||29 Sep 2011 21:11|
|Last Modified:||29 Sep 2011 21:11|
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