Fungal biomass was detected in peat soils from throughout the Everglades based on the presence of ergosterol. Ergosterol concentrations in soils were not detectably affected by the dominant plant, Cladium jamaicense or Typha domingensis, or phosphorus content of soils. In situ decomposition of decaying leaves, measured by respiration, was high (maximum 484 μl O2 h−1 g−1 dry biomass). Approximately 30% of respiration was by bacteria, and the rest was by fungi and other eukaryotes. Respiration rates were essentially the same for decomposing leaves of both plant species, with higher rates early in the decomposition process. Respiration rates were relatively unaffected by the nutrient status of the site, except for eukaryotic respiration on Cladium, which was usually higher at a high nutrient site. Ergosterol concentration increased in decaying leaves through time and was unrelated to the nutrient level except for Cladium, where it was higher at the high nutrient site. Eukaryotic respiration was not correlated with ergosterol concentration in decomposing leaves of Typha, but was positively correlated with ergosterol for Cladium.