Methane Emissions Vary by Rainfall in Wetland and are Mediated by Vegetation

Abstract

Investigating the effects of rainfall on methane emissions within wetlands, and the effect of the presence of vegetation. We measured methane flux using floating chambers with 3 replicates in two patches: Open Water (OPW) and Submerged Aquatic Vegetation (SAV), before and after storm events. Dissolved methane concentration was also investigated using Rhizons at two different depths (Shallow and Deep) with 3 replicates in OPW and SAV patches. We observed a trend that methane flux decreased after storms in the SAV patch, with an average difference of -114.18 ± 89.88 mg/m2/hr before and after, but the OPW patch’s mean and variance highly overlapped, seeming negligent with a mean difference of -4.28 ± 15.69 mg/m2/hr. For the dissolved methane, we found that the SAV patches generally increased in dissolved methane concentration, the Shallow depth average difference of 0.41 ± 0.23 𝛍mol/l before and after, while the deep had 41.34 ± 36.84 𝛍mol/l before and after. The dissolved methane in the OPW patches also highly overlapped, seeming negligent with a Shallow depth average difference of -0.45 ± 0.31 𝛍mol/l, and a Deep depth average difference of -4.89 ± 17.01 𝛍mol/l. A potential explanation for the negligent results from the OPW patch could be due to its fast methane recharge rate. While in the SAV patch, diffusive transport and pressurized gas flow can occur, releasing methane in the upper part of the water column. Increased photosynthesis after storm events could also lead to increased gas transport through plant tissue. This study shows that storm events can have important effects on wetland methane flux and complex interactions with vegetation.