Abstract Microbial degradation of organic carbon in marine sediments is a key driver of global element cycles on multiple time scales. However, it is not known to what depth microorganisms alter organic carbon in marine sediments or how microbial rates of organic carbon processing change with depth, and thus time since burial, on a global scale. To better understand the connection between the dynamic carbon cycle and life’s limits in the deep subsurface, we have combined a number of global data sets with a reaction transport model (RTM) describing first, organic carbon degradation in marine sediments deposited throughout the Quaternary Period and second, a bioenergetic model for microbial activity. The RTM is applied globally, recognizing three distinct depositional environments – continental shelf, margin and abyssal zones. The results include the masses of particulate organic carbon, POC, stored in three sediment-depth layers: bioturbated Holocene (1.7 × 1017 g C), non-bioturbated Holocene (2.5 × 1018 g C) and Pleistocene (1.4 × 1020 g C) sediments. The global depth-integrated rates of POC degradation have been determined to be 1.3 × 1015, 1.3 × 1014 and 3.0 × 1014 g C yr−1 for the same three layers, respectively. A number of maps depicting the distribution of POC, as well as the fraction that has been degraded have also been generated. Using POC degradation as a proxy for microbial catabolic activity, total heterotrophic processing of POC throughout the Quaternary is estimated to be between 10−11 and 10−6 g C cm−3 yr−1, depending on the time since deposition and location. Bioenergetic modeling reveals that laboratory-determined microbial maintenance powers are poor predictors of sediment biomass concentration, but that cell concentrations in marine sediments can be accurately predicted by combining bioenergetic models with the rates of POC degradation determined in this study. Our model can be used to quantitatively describe both the carbon cycle and microbial activity on a global scale for marine sediments less than 2.59 million years old.

中文翻译：

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整个第四纪全球范围内海洋沉积物中的有机碳和微生物活动

摘要 海洋沉积物中有机碳的微生物降解是多个时间尺度上全球元素循环的关键驱动因素。然而，在全球范围内，微生物改变海洋沉积物中有机碳的深度或有机碳加工的微生物速率如何随深度变化，以及自埋藏以来的时间如何变化，目前尚不清楚。为了更好地理解动态碳循环与深层地下生命极限之间的联系，我们将大量全球数据集与反应输运模型 (RTM) 结合起来，首先描述了整个第四纪沉积的海洋沉积物中的有机碳降解和第二，微生物活动的生物能模型。RTM 在全球范围内应用，识别三种不同的沉积环境——大陆架、边缘和深海带。结果包括储存在三个沉积深度层中的颗粒有机碳质量 POC：生物扰动的全新世 (1.7 × 1017 g C)、非生物扰动的全新世 (2.5 × 1018 g C) 和更新世 (1.4 × 1020 g C)沉积物。对于相同的三层，POC 降解的全局深度积分率已确定为 1.3 × 1015、1.3 × 1014 和 3.0 × 1014 g C yr-1。还生成了许多描绘 POC 分布的地图，以及已退化的部分。使用 POC 降解作为微生物分解代谢活动的代理，整个第四纪 POC 的总异养处理估计在 10-11 和 10-6 g C cm-3 yr-1 之间，这取决于自沉积以来的时间和位置。生物能模型表明，实验室确定的微生物维持能力不能很好地预测沉积物生物量浓度，但通过将生物能模型与本研究中确定的 POC 降解率相结合，可以准确预测海洋沉积物中的细胞浓度。我们的模型可用于定量描述不到 259 万年历史的海洋沉积物在全球范围内的碳循环和微生物活动。