Methane production and sulfate reduction in two Appalachian peatlands

Abstract

Anaerobic carbon mineralization was evaluated over a 1-year period in two Sphagnum-dominated peatlands, Big Run Bog, West Virginia, and Buckle's Bog, Maryland. In the top 35 cm of peat, mean rates of methane production, anaerobic carbon dioxide production, and sulfate reduction at Big Run Bog were 63,406 and 146 μmol L^-1 d^-1, respectively, and at Buckle's Bog were 18, 486 and 104 μmol L^-1 d^-1. Annual anaerobic carbon mineralization to methane and carbon dioxide at Big Run Bog and Buckle's Bog was 52.8 and 57.2 mol m^-2, respectively. Rates of methane production were similar to rates reported for other freshwater peatlands, but methane production accounted for only 11.7 and 2.8%, respectively, of the total anaerobic carbon mineralization at these two sites. Carbon dioxide production, resulting substantially from sulfate reduction, dominated anaerobic carbon mineralization. Considerable sulfate reduction despite low instantaneous dissolved sulfate concentrations (typically < 300 μmol L^-1 of substrate) was apparently fueled by oxidation and rapid turnover of the reduced inorganic sulfur pool.

The coincidence of high sulfate inputs to the Big Run Bog and Buckle's Bog watersheds through acid precipitation with the unexpected importance of sulfate reduction leads us to suggest a new hypothesis: peatlands not receiving high sulfate loading should exhibit low rates of anaerobic decomposition, and a predominance of methane production over sulfate reduction; however, if such peatlands become subjected to high rates of sulfur deposition, sulfate reduction may be enhanced as an anaerobic mineralization pathway with attendant effects on carbon balance and peat accumulation.