Coupled organic and inorganic carbon cycling in the deep subseafloor sediment of the northeastern Bering Sea Slope (IODP Exp. 323)
Coupled organic and inorganic carbon cycling in the deep subseafloor sediment of the northeastern Bering Sea Slope (IODP Exp. 323)
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DOI：
10.1016/j.chemgeo.2011.03.002
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发表时间：
2011-05
期刊：
影响因子：
3.9
通讯作者：
L. Wehrmann;N. Risgaard-Petersen;H. Schrum;Emily A. Walsh;Y. Huh;M. Ikehara;C. Pierre;S. D’Hondt;T. Ferdelman;A. Ravelo;Kozo Takahashi;C. Zarikian
中科院分区：
文献类型：
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作者：
L. Wehrmann;N. Risgaard-Petersen;H. Schrum;Emily A. Walsh;Y. Huh;M. Ikehara;C. Pierre;S. D’Hondt;T. Ferdelman;A. Ravelo;Kozo Takahashi;C. Zarikian
我们研究了微生物介导的成岩过程中驱动的碳矿化在东北白令海斜坡海底沉积物的深度为745米以下的海底（mbsf）。U1343、U1344和U1345是在综合大洋钻探计划（IODP）第323次考察期间钻探的，水深为1008至3172米。它们位于高生产力的“绿色带”区域，其有机碳埋藏率是西部大陆边缘高生产力上升流区的典型特征。这三个地点显示出很强的地球化学相似性。沉积物中微生物介导的过程的向下顺序包括（1）有机硫酸盐还原，（2）甲烷的厌氧氧化（AOM）与硫酸盐还原偶联，和（3）甲烷生成。沉积物包含两个不同的成岩碳酸盐形成区，位于硫酸盐-甲烷过渡区（SMTZ）和300和400 mbsf之间。三个站点的SMTZ位于6至9 mbsf之间。向上进入SMTZ的甲烷通量与智利和纳米比亚近海高产表层沃茨下SMTZ的甲烷通量相似。我们的白令海研究结果表明，强烈的有机碳矿化作用驱动了最高10 mbsf的高铵和溶解无机碳（DIC）生产率（> 4.2 mmol m− 3 y − 1），并强烈影响了DIC的稳定碳同位素组成，使其在SMTZ达到− 27‰（VPDB）的最低值。孔隙水的钙和镁的配置文件表明形成的成岩富镁方解石的SMTZ。在SMTZ以下，甲烷生成导致孔隙水DIC的13 C富集，最大值为+ 11.9‰。甲烷生成对DIC碳同位素组成的影响在150 mbsf的深度是明显的。在此深度以下，缓慢或缺乏微生物介导的碳矿化使DIC同位素组成不受影响。正在进行的碳酸盐形成之间的300和400 mbsf强烈影响孔隙水DIC和镁浓度的配置文件。我们在白令海陆坡沉积物中观察到的有机碳矿化和碳酸盐溶解和降水模式的连锁演替可能是世界海洋高生产力地区被动大陆边缘环境的代表。
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− 3y− 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 in13C-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.