Long‐term carbon sequestration by the ocean's recalcitrant dissolved organic carbon (RDOC) pool regulates global climate. Algae and bacteria interactively underpin RDOC formation. However, on the long‐term scales, the influence of their persistent interactions close to in situ state on ocean RDOC dynamics and accumulation remains unclear, limiting our understanding of the oceanic RDOC pool formation and future trends under global change. We show that a Synechococcus‐bacteria interaction model system viable over 720 days gradually accumulated high DOC concentrations up to 84 mg L−1. Concurrently, the DOC inertness increased with the RDOC ratio reaching > 50%. The identified Synechococcus‐bacteria‐driven RDOC molecules shared similarity with over half of those from pelagic ocean DOC. Importantly, we provide direct genetic and metabolite evidence that alongside the continuous transformation of algal carbon by bacteria to generate RDOC, Synechococcus itself also directly synthesized and released RDOC molecules, representing a neglected RDOC source with ~0.2–1 Gt y−1 in the ocean. However, we found that although ocean warming (+4°C) can promote algal and bacterial growth and DOC release, it destabilizes and reduces RDOC reservoirs, jeopardizing the ocean's carbon sequestration capacity. This study unveils the previously underestimated yet significant role of algae and long‐term algae‐bacteria interactions in ocean carbon sequestration and its vulnerability to ocean warming.

中文翻译：

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被忽视的持续藻类-细菌相互作用在海洋顽固碳封存及其对海洋变暖的响应中的重要作用


海洋顽固的溶解有机碳 （RDOC） 库的长期碳封存调节着全球气候。藻类和细菌相互作用地支持 RDOC 的形成。然而，从长期尺度上讲，它们接近原位状态的持续相互作用对海洋 RDOC 动力学和积累的影响仍不清楚，这限制了我们对海洋 RDOC 池形成和全球变化下未来趋势的理解。我们表明，在 720 天内存活的聚球藻-细菌相互作用模型系统逐渐积累了高达 84 mg L-1 的高 DOC 浓度。同时，DOC 惰性增加，RDOC 比率达到 > 50%。已鉴定的聚球菌驱动的 RDOC 分子与来自远洋海洋 DOC 的一半以上的分子具有相似性。重要的是，我们提供了直接的遗传和代谢物证据，证明除了细菌不断转化藻类碳以产生 RDOC 外，聚球菌本身也直接合成和释放 RDOC 分子，代表一种被忽视的 RDOC 来源，在海洋中具有 ~0.2-1 Gt y-1。然而，我们发现，尽管海洋变暖 （+4°C） 可以促进藻类和细菌的生长以及 DOC 的释放，但它会破坏和减少 RDOC 储层，从而危及海洋的碳封存能力。这项研究揭示了以前被低估的藻类和长期藻类-细菌相互作用在海洋碳封存中的重要作用及其对海洋变暖的脆弱性。