FUNGAL BIOMASS AND LEAF-LITTER PROCESSING IN STREAMS OF DIFFERENT WATER CHEMISTRY

Leaf litter processing rates and fungal biomass on leaf detritus were compared in four streams of different water chemistry. The streams drained catchments underlain by different bedrock types and varied in mean pH from 4.3 to 7.5 and in mean alkalinity from 0.0 to 35.8 mg CaCO3 1(-1). Processing rates were fastest in WS3 and WS4, which had a pH of 6.0; slowest in SFR, which had a pH of 4.3; and intermediate in HSR which had a pH of 7.5. Fungal biomass as measured by the fungal sterol, ergosterol, was similar in WS3, WS4, and HSR but was much lower in SFR. These results suggest that reduced processing rates in SFR were associated in part with reduced fungal biomass on the leaves, whereas reduced processing rates in HSR were not related to differences in fungal biomass on the leaves.