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The mangrove CO2 pump: Tidally driven pore‐water exchange
Limnology and Oceanography ( IF 4.5 ) Pub Date : 2021-01-21 , DOI: 10.1002/lno.11704
Xiaogang Chen 1, 2, 3 , Isaac R. Santos 1, 4 , Mitchell Call 1, 5 , Gloria M. S. Reithmaier 6 , Damien Maher 5, 6 , Ceylena Holloway 1 , Praktan D. Wadnerkar 1 , Paula Gómez‐Álvarez 5 , Christian J. Sanders 1 , Ling Li 2
Affiliation  

Atmospheric carbon dioxide (CO2) is fixed by mangrove vegetation and stored in its biomass and sediments. Part of the sediment carbon can be exported to coastal waters via tidally driven pore‐water exchange. Here, we quantify pore water‐derived dissolved CO2 export using in situ, high‐resolution observations of 222Rn and CO2 over a spring‐neap tidal cycle in a mangrove‐fringed estuary (Coffs Creek, Australia). 222Rn‐derived pore‐water exchange rates were 11.5–34.9 cm d−1 (23.0 ± 6.7) over 30 tidal cycles. Pore‐water exchange released CO2 from intertidal sediment at rates of 61–213 (136 ± 43) mmol m−2 d−1. This is equivalent to ~ 94% of the total CO2 input into the estuary and approximately two times of the water‐atmosphere CO2 emission. These observations reveal that tidal pumping is a major regulator of both mangrove pore‐water exchange and associated dissolved CO2 export to the ocean. Combining our estimates with literature data, a first‐order global pore water‐derived dissolved CO2 export from mangroves was estimated to be 83 ± 50 Tg C yr−1. This is higher than an earlier estimates of global mangrove CO2 emissions to the atmosphere (34.1 ± 5.4 Tg C yr−1) and carbon burial in sediments (18.4–34.4 Tg C yr−1), implying that pore water‐derived CO2 escapes to the atmosphere within and beyond mangrove waters. Overall, CO2‐rich pore water seems to be a widespread, important pathway of CO2 into mangrove‐dominated estuaries and should be considered in mangrove carbon assessments in the context of global climate change and blue carbon.

中文翻译:

红树林二氧化碳泵:潮汐驱动的孔隙水交换

大气二氧化碳(CO 2)由红树林植被固定并存储在其生物量和沉积物中。一部分沉积碳可以通过潮汐驱动的孔隙水交换输出到沿海水域。在这里,我们使用红树林边缘河口(春季,春季)潮汐周期中原位高分辨率观察到的222 Rn和CO 2,量化了孔隙水衍生的溶解的CO 2排放量(澳大利亚,科夫斯克里克)。在30个潮汐周期中,来自Rn的222种孔隙水交换速率为11.5-34.9 cm d -1(23.0±6.7)。孔隙水交换以61–213(136±43)mmol m -2 d -1的速率从潮间带沉积物中释放出CO 2。这相当于河口输入的CO 2总量的〜94%,约为水-大气CO 2排放量的两倍。这些观察结果表明,潮汐泵送是红树林孔隙水交换和相关的向海洋排放的溶解的CO 2的主要调节器。将我们的估计值与文献数据相结合,从红树林中导出的一阶全球毛孔水源溶解性CO 2出口估计为83±50 Tg C yr -1。这高于先前对全球红树林向大气中的CO 2排放量(34.1±5.4 Tg C yr -1)和沉积物中碳埋藏(18.4–34.4 Tg C yr -1)的早期估计。),这意味着来自毛孔水的CO 2会逸出到红树林水域之内和之外的大气中。总体而言,富含CO 2的孔隙水似乎是CO 2进入以红树林为主的河口的一种广泛而重要的途径,应在全球气候变化和蓝碳的背景下进行红树林碳评估时予以考虑。
更新日期:2021-01-21
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