First biomarker evidence for methane oxidation at cold seeps in the Southeast Atlantic (REGAB pockmark) |
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| Institution: | 1. Laboratoire d’Océanographie et du Climat—Expérimentation et Approches Numériques (LOCEAN), CNRS UMR 7159, Université Pierre et Marie Curie, IPSL, Case 100, 4 Place Jussieu, 75252 Paris Cedex 05, France;2. Organic Geochemistry Unit, Bristol Biogeochemistry Research Centre, School of Chemistry, University of Bristol, Cantock''s Close, Bristol BS8 1TS, UK;1. Institut Océanographique, 195 rue Saint-Jacques, 75005 Paris, France;2. Ifremer, Département DEEP/LEP,Centre de Brest, BP70, 29280 Plouzané, France;1. Organic Geochemistry Group, MARUM Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen, 28359 Bremen, Germany;2. Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307, USA;3. Institute of Geology, University of Hamburg, 20146 Hamburg, Germany;4. School of Geography, Earth and Environmental Sciences, University of Plymouth, Plymouth, Devon PL4 8AA, UK;5. State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China;6. Department of Geodynamics and Sedimentology, Center for Earth Sciences, University of Vienna, 1090 Vienna, Austria;1. CAS Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;2. Department of Earth Sciences and Geological Engineering, Sun Yat-Sen University, Guangzhou 510275, China;3. Shanghai Engineering Research Center of Hadal Science and Technology, College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, China;4. Guangzhou Marine Geological Survey, Guangzhou 510740, China;1. CAS Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;2. CAS Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;1. CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geosciences, UiT the Arctic University of Norway in Tromsø, Norway;2. NIOZ Royal Institute for Sea Research, Department of Marine Microbiology and Biogeochemistry, And Utrecht University, P.O. Box 59, 1790, AB Den Burg, Texel, the Netherlands;3. Department of Environmental Sciences, University of Basel, Bernoullistrasse 30, CH-4056, Basel, Switzerland |
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| Abstract: | Sediment cores from the REGAB pockmark, an active cold seep area in the southeast Atlantic, were analysed for their lipid biomarker distribution and associated stable carbon isotopic composition. Substantial amounts of diagnostic archaeal lipids were found, consisting mainly of archaeol, sn-2 hydroxyarchaeol and crocetane. All archaeal lipids were profoundly depleted in 13C with δ13C values as low as −133‰. Concurrently, abundant monoalkylglycerolethers (MAGE), assigned to sulphate-reducing bacteria, were identified and showed strong 13C-depletions (δ13C between −86‰ and −95‰). The structural and isotopic patterns of these microbial lipids provided compelling evidence for anaerobic oxidation of methane (AOM) occurring in REGAB sediments, mediated by archaea and sulphate reducing bacteria. Lipid fingerprints indicated that anaerobic methanotrophic archaea (ANME-2) and sulphate-reducing bacteria from the Desulfosarcina/Desulfococcus cluster are the dominant AOM assemblages. Depth profiles implied that highest AOM takes place below the upper 2 cm, mainly in the 6–12 cm depth interval. Significant abundances of 13C-depleted diploptene and 4α-methylsterols were found as well, inferring that aerobic methanotrophy occurs in the surface sediment interval. This first biomarker study at the recently investigated cold seeps in the SE Atlantic expand on existing work on AOM settings and add new evidence for aerobic and anaerobic methanotrophic communities occurring in close vicinity. |
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