Cyclic 100-ka (glacial-interglacial) migration of subseafloor redox zonation on the Peruvian shelf
Cyclic 100-ka (glacial-interglacial) migration of subseafloor redox zonation on the Peruvian shelf
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DOI：
10.1073/pnas.1305981110
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发表时间：
2013-11-05
影响因子：
11.1
通讯作者：
Jorgensen, Bo Barker
中科院分区：
文献类型：
--
作者：
Contreras, Sergio;Meister, Patrick;Jorgensen, Bo Barker
海底下微生物生命与海洋和大气条件之间的关系还知之甚少。我们研究了过去海底下微生物活动的成岩印记和脂肪生物标志物，以评估其对秘鲁陆架上钻探的沉积区段(海洋钻探计划第201条，第1229点)冰川-间冰期循环的反应。多层不同的成岩重晶石和白云石，即通常在硫酸盐-甲烷转变(SMT)时形成的矿物，比目前SMT在海底约30米以下的埋藏深度要浅得多。这些浅层与C-13耗尽的古醇的峰位共生，古醇是厌氧甲烷氧化古生代的分子化石。目前，溶解硫酸盐的非稳态分布也表明，SMT对表层陆架沉积物有机碳通量的变化高度敏感，这可能导致SMT的浅化。反应-输运模型证实了我们的假设，即浅层SMT是对间冰期有机碳通量高、冰期有机碳通量低的周期性沉积物沉积的响应。在相对较短的地质时间尺度上，如冰川-间冰期，较长的扩散距离预计会抑制深埋微生物群落对沉积物沉积和其他海洋学驱动因素变化的反应。然而，我们的研究展示了秘鲁边缘的动态沉积物生物地球化学如何响应冰川间冰期的变化，以及这些变化是如何被保存在地质记录中的。需要考虑到海底以下生物地球化学分区的这种变化，以评估海底以下生物圈在全球元素和氧化还原循环中的作用。
The coupling of subseafloor microbial life to oceanographic and atmospheric conditions is poorly understood. We examined diagenetic imprints and lipid biomarkers of past subseafloor microbial activity to evaluate its response to glacial-interglacial cycles in a sedimentary section drilled on the Peruvian shelf (Ocean Drilling Program Leg 201, Site 1229). Multiple and distinct layers of diagenetic barite and dolomite, i. e., minerals that typically form at the sulfate-methane transition (SMT), occur at much shallower burial depth than the present SMT around 30 meters below seafloor. These shallow layers co-occur with peaks of C-13-depleted archaeol, a molecular fossil of anaerobic methane-oxidizing Archaea. Presentday, non-steady state distributions of dissolved sulfate also suggest that the SMT is highly sensitive to variations in organic carbon flux to the surface shelf sediments that may lead to shoaling of the SMT. Reaction-transport modeling substantiates our hypothesis that shallow SMTs occur in response to cyclic sediment deposition with a high organic carbon flux during interglacials and a low organic carbon flux during glacial stages. Long diffusion distances expectedly dampen the response of deeply buried microbial communities to changes in sediment deposition and other oceanographic drivers over relatively short geological time scales, e. g., glacial-interglacial periods. However, our study demonstrates how dynamically sediment biogeochemistry of the Peru Margin has responded to glacialinterglacial change and how these changes are now preserved in the geological record. Such changes in subsurface biogeochemical zonation need to be taken into account to assess the role of the subseafloor biosphere in global element and redox cycling.