Seasonality of CO ₂ , CH ₄ , and N ₂ O Fluxes Reveal Seagrass Ecosystems as CO ₂ and N ₂ O Sink Attenuating Carbon Climate Impacts

Seagrass meadows are pivotal in coastal carbon cycling and climate regulation, yet simultaneous measurements of CO 2 , CH 4 , and N 2 O fluxes, especially in tropical systems, remain scarce. Here, we present the first synchronized seasonal assessment of these three greenhouse gases (GHGs) fluxes across water‐atmosphere in a tropical seagrass meadow (Li'an Lagoon, China). The ecosystem acted as a source of CH 4 to the atmosphere but absorbed substantially more warming potential in the form of CO 2 and N 2 O, resulting in a net atmospheric carbon sink. Notably, N 2 O uptake offset 63%–243% of the warming potential from CH 4 emissions. At the global scale, tropical seagrass meadows exhibit higher median CH 4 emissions yet stronger N 2 O uptake compared to temperate systems, also constituting a net GHGs sink from the atmosphere, with N 2 O uptake contributing 38%–164% of this sink effect. These findings highlight the necessity of multi‐gas assessments to accurately evaluate the climate function of seagrass ecosystems worldwide.