Carbon isotope biogeochemistry of acetate in sub-seafloor sediments in the Sea of Okhotsk near Sakhalin Island, Russia(<SPECIAL ISSUE>Advances in molecular and stable isotope studies among the organic geochemical and related communities (Part I))

概要

論文の詳細を見る
Biogeochemical processes involving acetate in sub-seafloor sediments were investigated by examining the stable carbon isotopic relationships of acetate and other relevant carbon-bearing materials (i.e., total organic carbon (TOC) and ΣCO_2) in five piston cores retrieved from the Sea of Okhotsk off Sakhalin Island, Russia. The cores were classified into two types on the basis of SO_4^<2-> content: (I) those with sulfate-reducing sediments in which the depletion of pore-water SO_4^<2-> with increasing depth was slight, and (II) those with methanogenic sediments in which SO_4^<2-> concentrations were less than 2mM more than 3m below the seafloor. Acetate was detected in all cores. The acetate content in methanogenic sediments (2.6-23.0μM) was relatively higher than in the sulfate-reducing sediment (2.8-8.8μM). In the sulfate-reducing sediments, the depth profiles of δ^<13>C_<acetate> approximately parallel those of δ^<13>C_<TOC>, with the δ^<13>C_<acetate> values (-39‰ to -33‰) depleted by about 12‰ relative to δ^<13>C_<TOC> (-24.5‰ to -22.3‰). These approximately parallel depth profiles suggest that the principal acetate production process in the sulfate-reducing sediments is fermentation of dissolved organic compounds. The fermentation products, however, tend to be similar or slightly enriched in ^<13>C compared to their substrates. Therefore, the ^<13>C depletion of acetate relative to TOC in the sulfate reduction zone suggests that some portion of the acetate was synthesized by acetogenesis in which the synthesized acetate is depleted in ^<13>C compared with its precursor. Given the large contribution of land-derived organic matter in the studied sediments, organoautotrophic acetogenesis using the lignin-derived syringate monomer, which originates from land plants, is likely. In the methanogenic sediments, the δ^<13>C_<acetate> values in sediments throughout the cores (-39‰ to -25‰) were depleted compared to δ^<13>C_<TOC> (-25.5‰ to -21.4‰). This suggests some acetogenic contribution to the total acetate production. The depth profiles of δ^<13>C_<acetate> in methanogenic sediments did not parallel those of either δ^<13>C_<TOC> or δ^<13>C_<ΣCO2>, probably because of the mixed isotopic effect from some production and consumption processes; namely fermentation, acetogenesis, and acetoclastic methanogenesis.
2010-12-24

Carbon isotope biogeochemistry of acetate in sub-seafloor sediments in the Sea of Okhotsk near Sakhalin Island, Russia(<SPECIAL ISSUE>Advances in molecular and stable isotope studies among the organic geochemical and related communities (Part I))

スポンサーリンク

概要

著者

関連論文

スポンサーリンク