2:15 PM - 2:30 PM
[BCG04-03] Methane fluxes, methanogenic, and methanotrophic activities, and microbial compositions in mangrove forests of Taiwan
Keywords:mangrove forests, methane emission, methanogen, methanotroph, DNA stable isotope probing, next generation sequencing
Mangrove forests play a crucial role as a significant blue carbon sink, aiding in the mitigation of elevated global CO2 concentrations. However, the anaerobic soil conditions created by mangrove forests may also promote anaerobic soil respiration, leading to stimulated methane emissions. Coastal wetlands are generally thought to have low methane (CH4) emissions due to the presence of sulfate ions (SO42-), which facilitate sulfate-reducing bacteria and compete with methanogens. However, direct evidence for this occurrence in mangrove ecosystems is lacking.
This study conducted a comprehensive analysis of CH4 emissions, methanogenic and methanotrophic activities, and the compositions of active methanogens and methanotrophs using DNA stable isotope probing (DNA-SIP) in mangrove forests in northern Taiwan.
The results revealed an in situ CH4 emission of 0.16-65.6 μmol CH4 m-2 hr-1. However, in the 2-5 cm soil depth, the methanogenic potential was significantly higher at 200-2,175 μmol CH4 m-2 hr-1, surpassing the in situ CH4 fluxes. Furthermore, in the 0-2 cm soil depth, the methanotrophic potential was 200-1100 μmol CH4 m-2 hr-1. This finding suggested that the observed low CH4 efflux in mangrove soils may be attributed to the high methane oxidizing rates from methanotrophs, compensating for the elevated methane production rates from methanogens in the mangrove soils.
Additionally, DNA-SIP results identified Type Ia methanotrophs, such as Methylomonas, Methylobacter, and Methylosarcina, as the predominant active methanotrophs. These organisms have previously demonstrated high CH4 oxidizing potential. On the other hand, active methanogens, particularly Methanosarcina, were found to be prevalent. Methanosarcina can use methanol as one of the carbon sources and do not compete with sulfate-reducing bacteria, unlike other acetoclastic methanogens.
The findings suggest that CH4 dynamics are active in mangrove forests, and CH4 release may occur if the delicate balance between methanotrophs and methanogens is disturbed.
This study conducted a comprehensive analysis of CH4 emissions, methanogenic and methanotrophic activities, and the compositions of active methanogens and methanotrophs using DNA stable isotope probing (DNA-SIP) in mangrove forests in northern Taiwan.
The results revealed an in situ CH4 emission of 0.16-65.6 μmol CH4 m-2 hr-1. However, in the 2-5 cm soil depth, the methanogenic potential was significantly higher at 200-2,175 μmol CH4 m-2 hr-1, surpassing the in situ CH4 fluxes. Furthermore, in the 0-2 cm soil depth, the methanotrophic potential was 200-1100 μmol CH4 m-2 hr-1. This finding suggested that the observed low CH4 efflux in mangrove soils may be attributed to the high methane oxidizing rates from methanotrophs, compensating for the elevated methane production rates from methanogens in the mangrove soils.
Additionally, DNA-SIP results identified Type Ia methanotrophs, such as Methylomonas, Methylobacter, and Methylosarcina, as the predominant active methanotrophs. These organisms have previously demonstrated high CH4 oxidizing potential. On the other hand, active methanogens, particularly Methanosarcina, were found to be prevalent. Methanosarcina can use methanol as one of the carbon sources and do not compete with sulfate-reducing bacteria, unlike other acetoclastic methanogens.
The findings suggest that CH4 dynamics are active in mangrove forests, and CH4 release may occur if the delicate balance between methanotrophs and methanogens is disturbed.