Linking biogeochemical signatures to archaeal community structure at active methane seeps in the Tatar trough, far eastern Russia

초록

The Tatar Trough lies off the eastern coast of Far Eastern Russia, extending into the northern part of the East Sea (also known as the Sea of Japan). This region is characterized by active tectonics and widespread gas seepage, making it an ideal natural laboratory for investigating the biogeochemical dynamics of gas-rich sediments. In this study, we analyzed two sediment cores, LV67-07HC and LV67-19HC, which were recovered from an active fault zone on the eastern slope during the 2014 SSGH expedition. Using a combination of lipid and nucleic acid analyses along with complementary measurements such as gas and porewater composition, we assessed the ecological roles of the archaeal communities inhabiting these seep environments. Both cores exhibited elevated concentrations of light hydrocarbon gases (primarily methane, CH4) and carbon dioxide, along with a distinct sulfate-methane transition zone (SMTZ). However, notable differences in porewater geochemistry, lipid biomarkers, and microbial community composition were observed between the two cores, reflecting variations in CH4 flux and subsurface fluid migration pathways within the underlying coal-bearing strata. In core LV67-07HC (91–185 cm depth), we observed notably high concentrations of 13C-depleted archaeal lipids in sediments surrounding carbonate accretions. These features suggest enhanced anaerobic methanotrophic activity under relatively higher CH4 flux conditions. Archaeal 16S rRNA gene sequences were dominated by members of the ANME-1 clade, consistent with previous observations in CH4-rich seep environments, and further constrained here within a site-specific, multi-proxy framework. To the best of our knowledge, this study provides new insights into how spatial differences in CH4 sources and subsurface fluid-migration pathways influence carbon cycling and archaeal community structure in CH₄-rich continental margin sediments.

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