Biogeochemical evidence of anaerobic methane oxidation on active submarine mud volcanoes on the continental slope of the Canadian Beaufort Sea

Lee, Dong-Hun; Kim, Jung-Hyun; Lee, Yung Mi; Stadnitskaia, Alina; Jin, Young Keun; Niemann, Helge; Kim, Young-Gyun; Shin, Kyung-Hoon

In this study, we report lipid biomarker patterns and phylogenetic identities of key microbial communities mediating anaerobic oxidation of methane (AOM) in active mud volcanoes (MVs) on the continental slope of the Canadian Beaufort Sea. The carbon isotopic compositions (inline-formulaδ13C) of sn-2- and sn-3-hydroxyarchaeol showed the highly inline-formula13C-depleted values (inline-formula−114 ‰ to inline-formula−82 ‰) associated with a steep depletion in sulfate concentrations within 0.7 m of sediment depths. This suggested the presence of methanotrophic archaea involved in sulfate-dependent AOM, albeit in a small amount. The ratio of sn-2-hydroxyarchaeol to archaeol (> 1) and operational taxonomic units (OTUs) indicated that the anaerobic methanotrophic archaea (ANME) clades ANME-2c and ANME-3 were involved in AOM. Higher inline-formulaδ13C values of archaeol and biphytanes (BPs; inline-formula M6inlinescrollmathml - normal 55.2 ± normal 10.0 64pt10ptsvg-formulamathimgb8a30afc3a6a907d1421600169c03687 bg-15-7419-2018-ie00001.svg64pt10ptbg-15-7419-2018-ie00001.png  ‰ and inline-formula M7inlinescrollmathml - normal 39.3 ± normal 13.0 64pt10ptsvg-formulamathimg8ab88b064bf7877fe9242b053f754cf0 bg-15-7419-2018-ie00002.svg64pt10ptbg-15-7419-2018-ie00002.png  ‰, respectively) suggested that archaeal communities were also assimilating AOM-derived inorganic carbon. Furthermore, the distinct distribution patterns of methanotrophs in the three MVs appears to be associated with varying intensities of ascending gas fluids. Consequently, our results suggest that the niche diversification of active mud volcanoes has shaped distinct archaeal communities that play important roles in AOM in the Beaufort Sea.

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Lee, Dong-Hun / Kim, Jung-Hyun / Lee, Yung Mi / et al: Biogeochemical evidence of anaerobic methane oxidation on active submarine mud volcanoes on the continental slope of the Canadian Beaufort Sea. 2018. Copernicus Publications.

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