EGU25-14176, updated on 16 Jul 2025
https://doi.org/10.5194/egusphere-egu25-14176
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Effect of tidal cycles on greenhouse gas emissions from mangroves
Masako Dannoura1, Sumonta Kumar Paul1, Rifat Rahaman Hredoy1, Rempei Suwa2, Minori Tokito1, and Daniel Epron1
Masako Dannoura et al.
  • 1Kyoto University, Graduate School of Agriculture, Division of Forest and Biomaterial Science, Kyoto, Japan (dannoura.masako.4w@kyoto-u.ac.jp)
  • 2Forestry Division, Japan International Research Center for Agricultural Sciences, Ibaraki, Japan

Mangrove forest is one of the most carbon storing tropical forests. Thus, understanding the dynamics of greenhouse gas such as CO2 and CH4 are important to predict the future. CO2 is produced by plant respiration, dissolved in water and transported upwards with transpiration. Active respiration in mangrove roots occurs because salt from seawater must be excluded before water enters the xylem. Therefore, tidal fluctuation can affect the exchange of CO2 between tree surface and the atmosphere. CH4 is produced in anaerobic conditions in the sediment and is not readily soluble in water. However, it can diffuse through aerenchyma and pores in root and stem tissues, particularly during the day when the water potential becomes low and tissue air porosity increases. Because CH4 has a global warming potential that is 25 times more powerful than CO2 over 100 years, CH4 emissions have the potential to offset a part of the CO2 initially removed from the atmosphere by photosynthesis and buried as blue carbon in the sediment. Thus, both CO2 and CH4 fluxes should be considered in the carbon budget of mangrove ecosystems. The aim of this study was to determine how tidal and diurnal cycles affect CO2 and CH4 emissions from mangrove roots and stems, both physiologically and physically, for a more accurate understanding of gas exchange processes in mangrove forests.
The research was conducted on Bruguiera gymnorrhiza and Rhizophora stylosa on the bank of the Miyara River in Ishigaki island. Chambers were placed at three heights along the stems (approximately 0.2, 1.0, and 1.5 m above the sediment) and on different root types to measure CO2 and CH4 fluxes during day and night and low and high tide in June, August and November 2024.
CO2 efflux from the trunk showed no difference with height. In contrast, CH4 efflux was highest at the base of the trunks. At low tide, CH4 emissions from the roots were much higher than those from the trunk. Both CO2 and CH4 efflux from the trunk surface was lower at night than during the day, and there was no difference between high and low tide. Large variations in CH4 efflux was observed from the same position at different times. Continuous measurements are needed to better characterize these temporal variations. Characterizing the spatial distribution of roots is also a future challenge.

How to cite: Dannoura, M., Paul, S. K., Hredoy, R. R., Suwa, R., Tokito, M., and Epron, D.: Effect of tidal cycles on greenhouse gas emissions from mangroves, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14176, https://doi.org/10.5194/egusphere-egu25-14176, 2025.