资源环境科技发展态势分析平台

Although methanogenesis is considered a strictly anaerobic process, oxygen‐replete surface open‐ocean waters are usually supersaturated with methane (CH₄), a phenomenon termed the oceanic methane paradox. Here we report that abiotic methane photoproduction from chromophoric dissolved organic matter (CDOM) significantly contributes to this paradox. Methane photoproduction was observed during solar‐simulated irradiations of various waters collected along the land‐ocean continuum. Methane photoproduction rates decreased seaward, whereas its relative production efficiency and the methane‐to‐carbon‐monoxide (CO) photoproduction ratio (ΔCH₄/ΔCO) both followed a reversed trend. Remote‐sensing modeling incorporating a ΔCH₄/ΔCO–CDOM absorption relationship yielded an annual methane photoproduction of 118 Gg for the global open ocean, accounting for 20‐60% of the open‐ocean methane efflux and being of comparable magnitude to the upper‐ocean methane microbial‐oxidation sink. The photodegradation of CDOM thus plays an important role in maintaining supersaturated methane concentrations in the oxygenated upper ocean and in sustaining oceanic methane emissions to the atmosphere.