Globally, water bodies adjacent to mangroves are considered significant sources of atmospheric CO₂. We directly measured the partial pressure of CO₂ in water [pCO₂(water)] and related biogeochemical parameters with high temporal resolution, covering both diel and tidal cycles, in the mangrove-surrounding waters around the northern Bay of Bengal during the post-monsoon season. Mean pCO₂(water) was marginally oversaturated in two creeks (470 ± 162 µatm, mean ± SD) and undersaturated in the adjoining estuarine stations (387 ± 58 µatm) compared to atmospheric pCO₂, and was considerably lower than the global average. We further estimated the pCO₂(water) and buffering capacity of all possible sources of the mangrove-surrounding waters and concluded that their character as a CO₂ sink or weak source is due to the predominance of marine water from the Bay of Bengal with low pCO₂ and high buffering capacity. Marine water with high buffering capacity suppresses the effect of pCO₂ increase within the mangrove system and lowers the CO₂ evasion even in creek stations. The δ¹³C of dissolved inorganic carbon (DIC) in the mangrove-surrounding waters indicated that the DIC sources were a mixture of mangrove plants, pore-water, and groundwater, in addition to marine water. Finally, we showed that the CO₂ evasion rate from the estuaries of the Sundarbans is much lower than the recently estimated world average. Our results demonstrate that mangrove areas having such low emissions should be considered when up-scaling the global mangrove carbon budget from regional observations.

在全球范围内，与红树林相邻的水体被认为是大气中CO _2的重要来源。我们直接测量了孟加拉北部海湾周围红树林周围水域中水中CO ₂的分压[ p CO ₂（水）]和相关的生物地球化学参数，具有较高的时间分辨率，涵盖了迪尔和潮汐周期。 -季风季节。与大气中的p CO ₂相比，平均p CO ₂（水）在两条小溪中略微过饱和（470±162 µatm，均值±SD），而在相邻的河口站（387±58 µatm）中不饱和，并且大大低于全球平均水平。我们进一步估计了红树林周围水域所有可能来源的p CO ₂（水）和缓冲能力，并得出结论，它们作为CO ₂汇或弱源的特征是由于孟加拉湾的海水占主导地位。低p CO ₂和高缓冲能力。具有高缓冲能力的海水抑制了红树林系统中p CO ₂增加的影响，甚至在小溪站中也降低了CO _2的逸出量。该δ ¹³围绕红树林的水中溶解的无机碳（DIC）的C表明，除海水外，DIC来源还包括红树林植物，孔隙水和地下水的混合物。最后，我们证明了从Sundarbans河口的CO ₂逃逸率远低于最近估计的世界平均水平。我们的结果表明，从区域观测结果扩大全球红树林碳预算时，应考虑排放量如此低的红树林地区。