Fluxes of dissolved organic carbon (DOC) from continental shelves to the ocean may play a critical role in marine carbon cycling and budget. However, these fluxes have been poorly constrained because complicated biogeochemical reactions of riverine, atmospheric, and marine organic carbon occur in continental shelf-waters. We used multiple tracers of DOC such as stable- and radiocarbon isotope ratios of DOC, fluorescent properties of dissolved organic matter (FDOM), and ²²⁸Ra as a water age tracer to investigate the sources and fluxes of DOC in the northwest Pacific continental margin of the East China Sea and the Yellow Sea. Here, we show that there are significant additional (excess) supplies of DOC in the central Yellow Sea relative to the Changjiang (Yangtze River) source, based on these tracers. The marine δ¹³C signature (−21.1 ± 1.1‰) and the radiocarbon age (2000 ± 400 yr) of DOC suggest that the additional DOC (Δ¹⁴DOC = −44‰) is supplied from a combination of newly produced DOC and the degradation of particulate as well as sedimentary organic matter. The flux of this additional DOC produced in the continental shelf of the East China Sea to the open ocean is estimated to be ~1.9 ± 0.8 Tg C yr⁻¹, which is comparable to that from the Changjiang discharge. Our study implies that the fluxes of continental shelf-borne DOC may be important globally and should be considered in estimating global DOC budgets in the marine environment.

从大陆架到海洋的溶解有机碳 (DOC) 通量可能在海洋碳循环和预算中发挥关键作用。然而，由于河流、大气和海洋有机碳的复杂生物地球化学反应发生在大陆架水域，这些通量受到的限制很差。我们使用了多种 DOC 示踪剂，例如 DOC 的稳定同位素和放射性碳同位素比、溶解有机物 (FDOM) 的荧光特性和²²⁸Ra作为水年龄示踪剂研究东海和黄海西北太平洋大陆边缘DOC的来源和通量。在这里，我们表明，基于这些示踪剂，黄海中部相对于长江（长江）源地存在大量额外（过量）的 DOC 供应。DOC的海洋 δ ¹³ C 特征 (-21.1 ± 1.1‰) 和放射性碳年龄 (2000 ± 400 年) 表明额外的 DOC (Δ ¹⁴ DOC = -44‰) 是由新产生的 DOC 和颗粒物和沉积有机物的降解。东海大陆架产生的这种额外的 DOC 到公海的通量估计为 ~1.9 ± 0.8 Tg C yr ^-1，这与长江排放量相当。我们的研究表明大陆架上的 DOC 通量可能在全球范围内很重要，在估算海洋环境中的全球 DOC 预算时应予以考虑。