Sulfur Cycling in a Cedar-Dominated, Freshwater Wetland

Rates of reduced sulfur production and quantification of S pools in anoxic peat of a New Jersey cedar swamp were determined over a 9-month period. Short-term anoxic incubations with $^35 SO_4^2-$ as a tracer produced not only labeled reduced inorganic S (RIS) compounds (e.g. $H_2S$, FeS, and $FeS_2$), but also labeled reduced orgnaic S, C-bonded sulfur (CBS), compounds. The rate of production of CBS compounds averaged 59% of the production of RIS compounds. Peat S pools for the top 10 cm were dominated by CBS (74% of total s), with RIS and ester sulfates each averaging only $\thicksim 13%$ of the total S. In the top 10 cm of peat, rates of reduced S production were very high relative to pool sizes, indicating that recycling of S in the peat is quite rapid. The high degree of recycling made detection of reduced S accumulation in the peat is quite rapid. The high degree of recycling made detection of reduced S accumulation in the peat impossible over the 9-month sampling period. Our data support an important role for $SO_4^2-$ reduction, however, in the retention of S in the cedar swamp of McDonalds Branch.