Coastal wetlands can serve as natural laboratories for assessing the future impacts of sea-level rise and the intricacies of the effect of sulfate (SO42-) on emissions of greenhouse gases, such as methane (CH4) and carbon dioxide. In the case of previously drained and freshened wetlands, we can observe how freshwater terrestrial microbial communities react and adapt to intrusion of SO42- rich saline waters. We conducted a 3-month anoxic incubation experiment with soil extracted from a peatland on the German Baltic coast which was rewetted with brackish water in late 2019 to examine how microbial communities at the site had adapted to the new conditions after two years. Soil slurries were incubated at a moderate temperature of 15 °C at two different salinities (reflecting surface water and average peat soil water salinity) and sampled at 8 timepoints. At each timepoint 5 replicates of each treatment were destructively harvested and sampled for concentrations of CH4, dissolved inorganic carbon (DIC), total aqueous organic carbon, SO42-, ammonium, and other major ions, pH values, qPCR analysis, and δ13DIC and δ13CH4 values.