Hypoxia has become a serious threat to the sustainability of marine ecosystems globally. As one of the leading components of eutrophication, river-delivered organic matter (ROM) regulates estuarine/coastal dissolved oxygen condition and contributes to hypoxia formation both directly via remineralization and indirectly via the nutrients released during remineralization. However, the impacts of ROM on the coastal environment have long been underestimated because the indirect contribution has been overlooked and left largely unknown. This study used the Changjiang River, the second-largest ROM source in the world, as a prototype. A coupled physical-biogeochemical model was used to explore the indirect contribution of Changjiang ROM to marginal sea deoxygenation and hypoxia formation. Here I show that ROM remineralization contributed 5.4% directly and 7.3% indirectly to the total oxygen consumption in the off-estuary hypoxic zone. The indirect contribution persistently sustained in a large part of the northwest Pacific marginal seas. Strict mitigation is required to manage the ecosystem impacts of deoxygenation. The findings of this study also indicate that river discharge, freshwater turbidity, and interactions between freshwater and shelf circulation are fundamental factors that regulate the contributions of ROM to hypoxia formation and shelf deoxygenation.

缺氧已成为全球海洋生态系统可持续性的严重威胁。作为富营养化的主要成分之一，河流输送的有机物 (ROM) 调节河口/沿海溶解氧条件，并通过再矿化直接和通过再矿化过程中释放的营养物质间接促进缺氧形成。然而，ROM 对沿海环境的影响长期以来一直被低估，因为间接贡献被忽视并且在很大程度上未知。本研究以世界第二大ROM源长江为原型。采用物理-生物地球化学耦合模型探索长江ROM对边缘海脱氧和缺氧形成的间接贡献。在这里，我表明 ROM 再矿化贡献了 5。4% 直接和 7.3% 间接对河口缺氧区的总耗氧量。间接贡献在西北太平洋边缘海的大部分地区持续存在。需要严格的缓解措施来管理脱氧对生态系统的影响。这项研究的结果还表明，河流流量、淡水浊度以及淡水和陆架循环之间的相互作用是调节 ROM 对缺氧形成和陆架脱氧的贡献的基本因素。