One of the key challenges in understanding the role of hadal trenches in the marine organic carbon (OC) cycle is the need to distinguish OC sources, assess accumulation rates, and identify controlling processes. To address this, sediment core samples from the southern Mariana Trench were analyzed for their contents and carbon isotopes (C and C) of both total OC (TOC) and saturated long-chain fatty acid (-LCFA). Our findings indicate that sedimentary OC in the southern Mariana Trench is primarily derived from marine sources, as indicated by TOC-δC values ranging from −19.9‰ to −17.0‰ and the ratios of TOC to total nitrogen (TOC/TN) of 5.5–8.4. The C ages of TOC and -LCFA ranged from 7159 to 22,662 yr and 8713 to 22,819 yr, respectively, with both showing gradual down-core increasing trends. This allows for a conservative estimation of sedimentation rate of 17.5–18.7 cm kyr in the southern Mariana Trench, leading to a sedimentary OC accumulation rate of 529–942 g C m kyr, which is 1–2 orders of magnitude higher than that observed in the abyssal plain. We propose that the continuous lateral downslope transport played a significant role in focusing pre-aged OC into the southern Mariana Trench. Therefore, hadal trenches are likely to accumulate substantial amounts of sedimentary OC in the deep ocean.

中文翻译：

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末次冰消期以来马里亚纳海沟南部预老化有机碳的持续沉积


了解深渊海沟在海洋有机碳 (OC) 循环中的作用的关键挑战之一是需要区分 OC 来源、评估积累速率并确定控制过程。为了解决这个问题，对来自马里亚纳海沟南部的沉积物岩心样本进行了总有机碳 (TOC) 和饱和长链脂肪酸 (-LCFA) 的含量和碳同位素（C 和 C）分析。我们的研究结果表明，马里亚纳海沟南部的沉积OC主要来自海洋，TOC-δ13C值范围为-19.9‰至-17.0‰，TOC与总氮的比率（TOC/TN）为5.5– 8.4. TOC和-LCFA的C年龄分别为7159年至22,662年和8713年至22,819年，均呈现逐渐向岩心增加的趋势。这允许保守估计马里亚纳海沟南部的沉积速率为 17.5–18.7 cm kyr，导致沉积 OC 积累速率为 529–942 g C m kyr，比观测到的高 1–2 个数量级。深渊平原。我们认为，连续的横向下坡输送在将预老化的 OC 集中到马里亚纳海沟南部方面发挥了重要作用。因此，超深渊海沟很可能在深海中积累大量的沉积有机碳。