TY - JOUR
T1 - Coupled organic and inorganic carbon cycling in the deep subseafloor sediment of the northeastern Bering Sea Slope (IODP Exp. 323)
AU - Wehrmann, Laura M.
AU - Risgaard-Petersen, Nils
AU - Takahashi, Kozo
AU - Zarikian, Carlos Alvarez
AU - Aiello, Ivano
AU - Asahi, Hirofumi
AU - Bartoli, Gretta
AU - Caissie, Beth
AU - Chen, Muhong
AU - Colmenero-Hidalgo, Elena
AU - Cook, Mea
AU - Dadd, Kelsie
AU - Schrum, Heather N.
AU - Guèrin, Gilles
AU - Husum, Katrine
AU - Ijiri, Akira
AU - Kender, Sev
AU - LaVigne, Douglas
AU - Liu, Tanzhuo
AU - Lund, Steve
AU - März, Christian
AU - Mix, Alan
AU - Ojha, Maheswar
AU - Walsh, Emily A.
AU - Okada, Makoto
AU - Okazaki, Yusuke
AU - Onodera, Jonaotaro
AU - Radi, Taoufik
AU - Sakamoto, Tatsuhiko
AU - Scholl, David
AU - Stroynowski, Zuzanna N.
AU - Huh, Youngsook
AU - Ikehara, Minoru
AU - Pierre, Catherine
AU - D'Hondt, Steven
AU - Ferdelman, Timothy G.
AU - Ravelo, Ana Christina
PY - 2011
Y1 - 2011
N2 - We studied microbially mediated diagenetic processes driven by carbon mineralization in subseafloor sediment of the northeastern Bering Sea Slope to a depth of 745 meters below seafloor (mbsf). Sites U1343, U1344 and U1345 were drilled during Integrated Ocean Drilling Program (IODP) Expedition 323 at water depths of 1008 to 3172 m. They are situated in the high productivity "Green Belt" region, with organic carbon burial rates typical of the high-productivity upwelling domains on western continental margins. The three sites show strong geochemical similarities. The downward sequence of microbially mediated processes in the sediment encompasses (1) organoclastic sulfate reduction, (2) anaerobic oxidation of methane (AOM) coupled to sulfate reduction, and (3) methanogenesis. The sediment contains two distinct zones of diagenetic carbonate formation, located at the sulfate–methane transition zone (SMTZ) and between 300 and 400 mbsf. The SMTZ at the three sites is located between 6 and 9 mbsf. The upward methane fluxes into the SMTZ are similar to fluxes in SMTZs underlying high-productivity surface waters off Chile and Namibia. Our Bering Sea results show that intense organic carbon mineralization drives high ammonium and dissolved inorganic carbon (DIC) production rates (> 4.2 mmol m⁻³3 y⁻¹) in the uppermost 10 mbsf and strongly imprints on the stable carbon isotope composition of DIC, driving it to a minimum value of − 27‰ (VPDB) at the SMTZ. Pore-water calcium and magnesium profiles demonstrate formation of diagenetic Mg-rich calcite in the SMTZ. Below the SMTZ, methanogenesis results in ¹³C-enrichment of pore-water DIC, with a maximum value of + 11.9‰. The imprint of methanogenesis on the DIC carbon isotope composition is evident down to a depth of 150 mbsf. Below this depth, slow or absent microbially mediated carbon mineralization leaves DIC isotope composition unaffected. Ongoing carbonate formation between 300 and 400 mbsf strongly influences pore-water DIC and magnesium concentration profiles. The linked succession of organic carbon mineralization and carbonate dissolution and precipitation patterns that we observe in the Bering Sea Slope sediment may be representative of passive continental margin settings in high-productivity areas of the world's ocean.
AB - We studied microbially mediated diagenetic processes driven by carbon mineralization in subseafloor sediment of the northeastern Bering Sea Slope to a depth of 745 meters below seafloor (mbsf). Sites U1343, U1344 and U1345 were drilled during Integrated Ocean Drilling Program (IODP) Expedition 323 at water depths of 1008 to 3172 m. They are situated in the high productivity "Green Belt" region, with organic carbon burial rates typical of the high-productivity upwelling domains on western continental margins. The three sites show strong geochemical similarities. The downward sequence of microbially mediated processes in the sediment encompasses (1) organoclastic sulfate reduction, (2) anaerobic oxidation of methane (AOM) coupled to sulfate reduction, and (3) methanogenesis. The sediment contains two distinct zones of diagenetic carbonate formation, located at the sulfate–methane transition zone (SMTZ) and between 300 and 400 mbsf. The SMTZ at the three sites is located between 6 and 9 mbsf. The upward methane fluxes into the SMTZ are similar to fluxes in SMTZs underlying high-productivity surface waters off Chile and Namibia. Our Bering Sea results show that intense organic carbon mineralization drives high ammonium and dissolved inorganic carbon (DIC) production rates (> 4.2 mmol m⁻³3 y⁻¹) in the uppermost 10 mbsf and strongly imprints on the stable carbon isotope composition of DIC, driving it to a minimum value of − 27‰ (VPDB) at the SMTZ. Pore-water calcium and magnesium profiles demonstrate formation of diagenetic Mg-rich calcite in the SMTZ. Below the SMTZ, methanogenesis results in ¹³C-enrichment of pore-water DIC, with a maximum value of + 11.9‰. The imprint of methanogenesis on the DIC carbon isotope composition is evident down to a depth of 150 mbsf. Below this depth, slow or absent microbially mediated carbon mineralization leaves DIC isotope composition unaffected. Ongoing carbonate formation between 300 and 400 mbsf strongly influences pore-water DIC and magnesium concentration profiles. The linked succession of organic carbon mineralization and carbonate dissolution and precipitation patterns that we observe in the Bering Sea Slope sediment may be representative of passive continental margin settings in high-productivity areas of the world's ocean.
KW - Bering Sea
KW - Deep subseafloor sediment
KW - Integrated Ocean Drilling Program
KW - Microbially mediated diagenetic processes
KW - Organic carbon mineralization
KW - Diagenetic carbonate formation
U2 - 10.1016/j.chemgeo.2011.03.002
DO - 10.1016/j.chemgeo.2011.03.002
M3 - Article
SN - 0009-2541
VL - 284
SP - 251
EP - 261
JO - Chemical Geology
JF - Chemical Geology
IS - 3-4
ER -