Abstract: The isopod Oniscus asellus was used to examine the direct and indirect effects of macrofaunal feeding on sulfur constituents of leaf litter, and to examine the effects of macrofauna on the nutrient dynamics of the organic (Oie and Oa) horizons. The consumption of leaf litter by the isopod simultaneously exhibited mineralization of carbon-bonded sulfur and immobilization of sulfate. Microbial decomposition of the fecal material showed a decrease in sulfate and increases in carbon-bonded sulfur and ester sulfate (relative to total sulfur). Simulated leachates of soils inhabited by isopods showed higher losses of Oie horizon K and Oa horizon Ca, Mg, and sulfate and lesser losses of Oie horizon Ca and Oa horizon dissolved carbon-bonded sulfur than those soils without isopods. No sulfur constituent changes (except for leached sulfate and dissolved carbon-bonded sulfur) were found in either horizon soil with or without isopods. The direct enhancement of the decomposition rates by macrofauna is believed to be a major factor affecting changes in the nutrient dynamics.