Effects of Tidal Scenarios on the Methane Emission Dynamics in the Subtropical Tidal Marshes of the Min River Estuary in Southeast China

In order to accurately estimate the effects of tidal scenarios on the CH(4) emission from tidal wetlands, we examined the CH(4) effluxes, dissolved CH(4) concentrations, and environmental factors (including in situ pH, Eh and electrical conductivity, porewater SO(4)(2−), NO(3)(−), and NH(4)(+)) during inundation and air-exposure periods in high- and low-tide seasons in the Min River Estuary in southeast China. By applying static and floating chambers, our results showed that the CH(4) effluxes during the inundation periods were relatively constant and generally lower than those during the air-exposed periods in both seasons. When compared, the CH(4) effluxes during the air-exposed periods were significantly higher in the high-tide season than those in the low-tide season. In contrast, CH(4) effluxes during the inundation periods were significantly lower in the high-tide season than those in the low-tide season. During the inundation periods, dissolved CH(4) concentrations were inversely proportional to in situ Eh. Under air-exposed conditions, CH(4) effluxes were proportional to in situ pH in both seasons, while the dissolved CH(4) concentrations were negatively correlated with the porewater SO(4)(2−) concentrations in both seasons. Our results highlighted that CH(4) effluxes were more dynamic between inundation and air-exposure periods compared to low- and high-tide seasons.