Simultaneous inhibition of CH4 efflux and stimulation of sulphate reduction in peat subject to simulated acid rain

Acid rain sulphate (SO42−) deposition is a known suppressant of methane (CH4) emission from wetlands. However, the hypothesised mechanism responsible for this important biogeochemical interaction, competitive exclusion of methanogens by dissimilatory SO42− reducing bacteria (SRB), lacks supporting evidence. Here, we present data from an acid rain simulation experiment in the Moidach More peat bog of NE Scotland that strengthens this hypothesis. We report a tenfold increase in estimated SO42− reduction during periods when measured CH4 emission rates were suppressed relative to controls receiving only one-tenth the SO42− of treated plots, but no treatment effect on potential methane oxidation. This tenfold increase in estimated SO42− reduction indicates the presence of a more active population of SRB in plots where CH4 emissions were reduced by over 30%.