Sulfide oxidation appeared to represent the majority of the SOD in shrimp ponds in Texas by the end of the growing season, where it accounted for about 84% of the total SOD (Suplee and Cotner, 1996). Alongi et al. (1999) estimated that the contribution to carbon oxidation was 41–60% through O2 respiration, 7–22% from Mn reduction, 5– 25% from iron reduction and 13–26% from sulfate reduction in shrimp pond sediments.