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

Abstract

TS2In 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 (d13C) of sn-2- and sn-3-hydroxyarchaeol showed the highly 13C-depleted values (-114‰ to -82 ‰) associated with a steep depletion in sulfate concentrations within 0.7m of sediment depths. This suggested the presence of methan otrophic 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 archaea of the anaerobic methanotrophic archaea (ANME) CE2 clades ANME-2c and ANME-3 were 15 involved in AOM. Higher d13C values of archaeol and biphytanes (BPs; -55.2+/-10.0‰ and -39.3+/-13.0 ‰, 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.