Coastal vegetated habitats like seagrass meadows can mitigate anthropogenic carbon emissions by sequestering CO₂ as “blue carbon” (BC). Already, some coastal ecosystems are actively managed to enhance BC storage, with associated BC stocks included in national greenhouse gas inventories. However, the extent to which BC burial fluxes are enhanced or counteracted by other carbon fluxes, especially air‐water CO₂ flux (FCO₂) remains poorly understood. In this study, we synthesized all available direct FCO₂ measurements over seagrass meadows made using atmospheric Eddy Covariance, across a globally representative range of ecotypes. Of the four sites with seasonal data coverage, two were net CO₂ sources, with average FCO₂ equivalent to 44%–115% of the global average BC burial rate. At the remaining sites, net CO₂ uptake was 101%–888% of average BC burial. A wavelet coherence analysis demonstrated that FCO₂ was most strongly related to physical factors like temperature, wind, and tides. In particular, tidal forcing was a key driver of global‐scale patterns in FCO₂, likely due to a combination of lateral carbon exchange, bottom‐driven turbulence, and pore‐water pumping. Lastly, sea‐surface drag coefficients were always greater than the prediction for the open ocean, supporting a universal enhancement of gas‐transfer in shallow coastal waters. Our study points to the need for a more comprehensive approach to BC assessments, considering not only organic carbon storage, but also air‐water CO₂ exchange, and its complex biogeochemical and physical drivers.

中文翻译：

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大气涡动协方差揭示了海草草甸上空气-水CO2交换的全球趋势

通过将CO ₂封存为“蓝碳”（BC），沿海植被带动的栖息地（如海草草甸）可以减轻人为的碳排放。已经对一些沿海生态系统进行了积极管理，以提高卑诗省的储存能力，并将相关的卑诗省存量纳入国家温室气体清单中。但是，人们对BC埋藏通量在多大程度上被其他碳通量（特别是空气-水CO ₂通量（FCO ₂））增强或抵消的程度了解甚少。在这项研究中，我们对全球代表性生态类型范围内使用大气涡度协方差进行的海草草甸上所有可用的直接FCO ₂测量值进行了合成。在四个具有季节性数据覆盖范围的站点中，两个站点的净CO _2为来源，平均FCO ₂相当于全球平均卑诗省埋葬率的44％–115％。在其余地点，净CO ₂吸收量为平均BC埋葬量的101％–888％。小波相干分析表明，FCO ₂与诸如温度，风和潮汐等物理因素关系最密切。特别是，潮汐强迫是FCO ₂中全球尺度模式的关键驱动力，这可能是由于侧向碳交换，底部驱动的湍流和孔隙水泵的结合所致。最后，海面阻力系数始终大于对开阔海洋的预测，支持普遍提高浅海沿岸的气体转移。我们的研究指出，不仅需要考虑有机碳存储，还应考虑空气-水CO ₂交换，以及其复杂的生物地球化学和物理驱动因素，需要一种更全面的BC评估方法。