2026-03-06 ロードアイランド大学（URI)
This diagram is a representation of differential carbon (blue) and phosphorus (pink) cycling following enhanced surface productivity. (Diagram by Megan Sullivan and Judith Camps-Castellá)
＜関連情報＞
- https://www.uri.edu/news/2026/03/interaction-of-carbon-and-nutrient-cycles-overlooked-in-marine-carbon-dioxide-strategies/
- https://www.pnas.org/doi/10.1073/pnas.2514991123
地球規模の海洋における有機炭素とリンの循環の分離した時間スケール Decoupled timescales of organic carbon and phosphorus recycling in the global ocean
Megan R. Sullivan, François W. Primeau, Hojong Seo, +2 , and Adam C. Martiny
Proceedings of the National Academy of Sciences Published:February 17, 2026
DOI:https://doi.org/10.1073/pnas.2514991123
Significance
The ocean plays a critical role in regulating atmospheric carbon dioxide through the biological carbon pump, which transports organic carbon from surface waters to the deep ocean. However, the efficiency of this process is influenced by the cycling of other essential nutrients, such as phosphorus. This study demonstrates that carbon and phosphorus have distinct residence times in the ocean, challenging assumptions about how much carbon remains sequestered over climate-relevant timescales. Our results suggest that assessments of proposed marine carbon dioxide removal strategies, such as ocean iron fertilization, may be inaccurate if they fail to account for nutrient cycling.
Abstract
The ocean’s biological carbon pump exports atmospheric CO2 to the deep ocean, where it can remain sequestered for decades to centuries, and attempts to artificially enhance this natural carbon sink by fertilizing portions of the open ocean could help mitigate the impacts of excessive anthropogenic CO2 emissions. However, differences in the cycling rates of carbon and other nutrients may impact the long-term response to ocean fertilization. In this study, we use a steady-state global biogeochemical inverse model, optimized to match hydrographic observations, to examine how differential production, remineralization, and circulation-driven re-exposure timescales of organic carbon and phosphorus affect long-term carbon sequestration. We partition global organic matter production based on the time required for regenerated carbon and phosphorus to return to the ocean surface. We find that less than 15% of total organic carbon and 31% of total organic phosphorus production remains sequestered in the ocean interior for ≥ 1 y, with only 3.3% (1.8 Pg C y−1) and 8.3% (0.046 Pg P y−1), respectively, remaining for a century or longer. The C:P ratio of the sequestration flux declines with increasing residence time, from 255:1 for total production to 98:1 for material sequestered for 100+ years, indicating that carbon is recycled to the surface more rapidly than phosphorus. This decoupling between carbon and phosphorus sequestration timescales could result in a “productivity hangover,” where the slow recovery of surface phosphate leads to a long-term suppression of global productivity, reducing the net removal of atmospheric CO2.
