Mangrove soils are highly enriched in organic carbon. Tidal pumping drives seawater and oxygen into mangrove soils during flood tide and releases carbon-rich porewater during ebb tides. Here, we resolve semi-diurnal (flood/ebb tides), diel (day/night) and weekly (neap/spring tides) drivers of porewater-derived CO fluxes in two mangroves and update global estimates of CO emissions building on earlier observations from other sites. Tidal pumping controlled CO variability within the two mangrove creeks. The highest values of CO (2,585–6,856 µatm) and Rn (2,315–6,159 dpm m) and lowest values of pH (6.8–7.1) and dissolved oxygen (1.7–3.7 mg L) at low tides were due to enhanced porewater export. Rn and CO in mangrove porewater were 4–15 and 38–41 times greater than surface waters, respectively. CO increased by 50 ± 30 % from high to low tide, 9 ± 22 % from day to night and 57 ± 5 % from neap to spring tide with clear changes in hourly, diel, and weekly time scales. Combining our new estimates with literature data, global porewater-derived (16 sites) and water-atmosphere (52 sites) CO fluxes in mangroves would upscale to 45 ± 12 and 41 ± 10 Tg C y, respectively. These fluxes represent 25 % of net primary production and are twice as high as the sediment carbon burial rates in global mangroves. Overall, our local observations and global compilation suggest that porewater-derived CO exchange is a major but often unaccounted source of CO in mangroves. The porewater-derived CO can be emitted to the atmosphere or laterally exported to the ocean and should be included in carbon budgets to solve global imbalances.

中文翻译：

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潮汐驱动的孔隙水交换和昼夜循环在局部和全球范围内控制红树林的二氧化碳通量


红树林土壤富含有机碳。潮汐泵在涨潮时将海水和氧气驱入红树林土壤，并在落潮时释放富含碳的孔隙水。在这里，我们解决了两个红树林中孔隙水衍生的二氧化碳通量的半日（涨潮/落潮）、昼夜（白天/夜间）和每周（小潮/春潮）驱动因素，并根据早期观测更新了全球二氧化碳排放估计其他网站。潮汐抽水控制了两条红树林小溪内的二氧化碳变化。低潮时 CO (2,585–6,856 µatm) 和 Rn (2,315–6,159 dpm m) 的最高值以及 pH 值 (6.8–7.1) 和溶解氧 (1.7–3.7 mg L) 的最低值是由于孔隙水输出增强。红树林孔隙水中的 Rn 和 CO 分别比地表水高 4-15 倍和 38-41 倍。从高潮到低潮，CO 增加了 50 ± 30%，从白天到夜间增加了 9 ± 22%，从小潮到大潮增加了 57 ± 5%，每小时、每昼夜和每周的时间尺度都有明显的变化。将我们的新估计与文献数据相结合，红树林中全球孔隙水来源（16 个地点）和水-大气（52 个地点）的 CO 通量将分别提升至 45 ± 12 和 41 ± 10 Tg C y。这些通量占净初级生产力的 25%，是全球红树林沉积物碳埋藏率的两倍。总体而言，我们的当地观察和全球汇编表明，孔隙水产生的二氧化碳交换是红树林中二氧化碳的主要但往往未被考虑的来源。孔隙水产生的二氧化碳可以排放到大气中或横向排放到海洋，应纳入碳预算以解决全球失衡问题。