Dissolved organic carbon (DOC) in the global oceans is an important long-term carbon sink. Connections between molecular size, reactivity, and isotopic characteristics show that DOC exists on a continuum from biologically reactive to recalcitrant. The driving mechanisms behind the creation and persistence of recalcitrant DOC remain unknown. We show mean recalcitrant DOC (isolated via solid-phase extraction; SPE-DOC) δ¹³C values are 1.3 ± 0.6‰ lower than mean total DOC δ¹³C between depth ranges 0–200 m and 2–4 km on three GO-SHIP Repeat Hydrography cruises. Lowest observed δ¹³C values correlate with low ∆¹⁴C and proximity to deep ocean hydrothermal systems. These data support the hypothesis that reworking of DOC through the microbial carbon pump is a key driver of the ocean's long-term carbon sink. Mass-balance modeling shows deep-ocean DOC not captured by SPE is enriched in ¹³C, highlighting the need for continued research on non-retained DOC to predict mechanisms that drive ocean carbon storage.

中文翻译：

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全球难溶有机物微生物封存的稳定同位素 (δ13C) 证据

全球海洋中的溶解有机碳（DOC）是重要的长期碳汇。分子大小、反应性和同位素特征之间的联系表明，DOC 存在于从生物反应性到顽固性的连续体中。顽固 DOC 的产生和持续存在背后的驱动机制仍然未知。我们显示，在三个 GO- 深度范围 0–200 m 和 2–4 km 之间，平均顽固 DOC（通过固相萃取分离；SPE-DOC）δ ¹³ C值比平均总 DOC δ ¹³ C低 1.3 ± 0.6 ‰。船舶重复水文巡航。观测到的最低δ ¹³ C值与低 Δ ¹⁴ C和靠近深海热液系统相关。这些数据支持这样的假设：通过微生物碳泵对 DOC 进行再加工是海洋长期碳汇的关键驱动因素。质量平衡模型显示，未被 SPE 捕获的深海 DOC 在¹³ C中富集，这凸显了需要继续研究非保留的 DOC，以预测驱动海洋碳储存的机制。