Tidally driven porewater exchange and diel cycles control CO2 fluxes in mangroves on local and global scales

Alex Cabral; Yvonne Y. Y. Yau; Gloria M. S. Reithmaier; Luiz C. Cotovicz Jr; Joao Barreira; Goeran Brostroem; Barbara Viana; Alessandra L. Fonseca; Isaac R. Santos

doi:10.1016/j.gca.2024.04.020

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Tidally driven porewater exchange and diel cycles control CO2 fluxes in mangroves on local and global scales

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Tidally driven porewater exchange and diel cycles control CO2 fluxes in mangroves on local and global scales

Alex Cabral, Yvonne Y. Y. Yau, Gloria M. S. Reithmaier, Luiz C. Cotovicz Jr, Joao Barreira, Goeran Brostroem, Barbara Viana, Alessandra L. Fonseca and Isaac R. Santos

Geochimica et cosmochimica acta, Vol.374, pp.121-135

01/06/2024

DOI: https://doi.org/10.1016/j.gca.2024.04.020

Appears in Recent Faculty of Science and Engineering Publications

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Abstract

222Rn

Radon mass-balance

Greenhouse gases

Blue carbon

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 2 fluxes in two mangroves and update global estimates of CO 2 emissions building on earlier observations from other sites. Tidal pumping controlled p CO 2 variability within the two mangrove creeks. The highest values of p CO 2 (2,585 - 6,856 mu atm) and 222 Rn (2,315 - 6,159 dpm m -3 ) and lowest values of pH (6.8 - 7.1) and dissolved oxygen (1.7 - 3.7 mg L -1 ) at low tides were due to enhanced porewater export. 222 Rn and p CO 2 in mangrove porewater were 4 - 15 and 38 - 41 times greater than surface waters, respectively. p CO 2 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 wateratmosphere (52 sites) CO 2 fluxes in mangroves would upscale to 45 +/- 12 and 41 +/- 10 Tg C y -1 , 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 2 exchange is a major but often unaccounted source of CO 2 in mangroves. The porewater-derived CO 2 can be emitted to the atmosphere or laterally exported to the ocean and should be included in carbon budgets to solve global imbalances.

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Title: Tidally driven porewater exchange and diel cycles control CO2 fluxes in mangroves on local and global scales
Creators: Alex Cabral - University of Gothenburg
Yvonne Y. Y. Yau - University of Gothenburg
Gloria M. S. Reithmaier - University of Gothenburg
Luiz C. Cotovicz Jr - Leibniz Institute of Plant Genetics and Crop Plant Research
Joao Barreira - Universidade Federal Fluminense
Goeran Brostroem - University of Gothenburg
Barbara Viana - Universidade Federal de Santa Catarina
Alessandra L. Fonseca - Universidade Federal de Santa Catarina
Isaac R. Santos - University of Gothenburg
Publication Details: Geochimica et cosmochimica acta, Vol.374, pp.121-135
Publisher: Elsevier
Number of pages: 15
Grant note: 2019-03930; 2020-00457 / Swedish Research Council
Identifiers: 991013204072502368
Academic Unit: Faculty of Science and Engineering
Language: English
Resource Type: Journal article

Tidally driven porewater exchange and diel cycles control CO2 fluxes in mangroves on local and global scales

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