Biomarkers for aerobic methanotrophy in the water column of the stratified Gotland Deep (Baltic Sea) |
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| Affiliation: | 1. Geobiology Group, Geoscience Centre, Georg-August-University Göttingen, Goldschmidtstr. 3, 37077 Göttingen, Germany;2. Leibniz Institute for Baltic Sea Research Warnemünde (IOW), Seestr. 15, 18119 Rostock-Warnemünde, Germany;1. Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique (LESIA), Observatoire de Paris, CNRS, UPMC, Paris Diderot Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon, France;2. Space Exploration Sector, Johns Hopkins University Applied Physics Lab, Laurel, MD 20723, USA;3. Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS-IPSL), Université Versailles St-Quentin (UVSQ), 11 bd d’Alembert, 78 280 Guyancourt, France;1. Department of Earth Sciences (Geochemistry), Faculty of Geosciences, Utrecht University, P.O. Box 80.021, 3508 TA Utrecht, The Netherlands;2. Department of Estuarine and Delta Systems, Royal Netherlands Institute for Sea Research, Yerseke, The Netherlands;3. Dutch-Belgian Beamline (DUBBLE), ESRF – The European Synchrotron, CS 40220, 38043 Grenoble Cedex 9, France;4. Department of Analytical, Environmental- and Geo-chemistry, Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium;1. Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK;2. Department of Earth Sciences, Royal Holloway, University of London, Egham TW20 0EX, UK |
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| Abstract: | Filter samples from the oxic zone and suboxic zone of the physically stratified water column and sediment samples of the Gotland Deep, Baltic Sea, were analyzed for bacteriohopanepolyol (BHP) and phospholipid fatty acid (PLFA) concentrations. In total, eight BHPs were identified, with the greatest diversity in the suboxic zone. There, 35-aminobacteriohopane-31,32,33,34-tetrol (aminotetrol) and 35-aminobacteriohopane-30,31,32,33,34-pentol (aminopentol), whose concentrations decreased concurrently from the lower to the upper suboxic zone, indicated type I methanotrophic bacteria and thus aerobic oxidation of methane. The presence and activity of type I aerobic methanotrophic bacteria was further supported by the presence of 13C-depleted PLFAs, specifically 16:1ω8c and 16:1ω5c (δ13C as low as −41.2‰). However, the relative amount of methanotroph-specific compounds was low (aminopentol, <0.2% of total BHPs; 16:1ω8c, ca. 0.5% of total PLFAs), suggesting a minor contribution of aerobic methanotrophic bacteria to the particulate organic matter. The distinctive BHP pattern in the suboxic zone, including aerobic methanotroph biomarkers and a tentative marker for a pelagic redoxcline [putative 22S isomer of the ubiquitous 22R-bacteriohopanetetrol (BHT)], was mirrored in the sediment samples. Our data indicate that a major portion of the sedimentary hopanoids of the Gotland Deep is sourced from the suboxic part of the water column via an effective but unknown transport mechanism. |
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