Methane seepages from natural process or gas hydrate dissociation are proposed to cause adverse effect of climate change. The ultimate fate of methane leakage from the deep sea is less understood. Here, a systematic investigation of dissolved methane intensity, characteristic of pore fluid migration, metallogenic features of the sediment, and evolutions of biological communities in different methane seeping areas was conducted by high-resolution image, pore fluid geochemical analysis, and lithologic and surface analysis of the sediment. Results indicate that with high methane flux, biogeochemical progresses dominated by AOM in sediments, excess methane emissions to seawater and the methane metabolic communities dominate. While at low methane fluxes, AOM co-exists with OSR. This work reveals the dynamic marine methane cycle mechanism in different seepage intensities.
Keywords natural gas hydrate, methane seepage intensity, biogeochemical footprints, community succession sequence