Research conducted in New Zealand compared the composition of the biofilm colonizing wood to that colonizing rocks and leaves in streams. Additionally, wood biofilms were compared in naturally acidic and circumneutral streams to determine the effect of stream water pH on biofilm development. Similar biofilms developed on wood veneer, natural twigs, and beech leaves, but fungi did not colonize stones where diatoms were the predominant colonizer. Comparing wood incubated on the stream bed surface to wood buried beneath the stream bed, fungal hyphae dominated the biofilm but actinomycetes and bacteria were also present. An assay of microbial activity (14C glucose uptake) indicated that surface biofilms were more active than biofilms on buried wood. There was no relationship between 14C glucose uptake and stream pH indicating that acidity did not affect wood biofilm activity in these streams.

The processes governing wood biofilms in the presence and absence of leaf litter in 2 small mountain streams at Coweeta Hydrologic Laboratory in the southern Appalachians of the United States were also examined. Microbial respiration, fungal biomass, extracellular enzyme activity, and the effect of nutrient addition were used as descriptors of wood biofilms. Exclusion of leaf litter from a headwater stream enhanced extracellular enzyme activity, and fungal biomass was 7 times higher than that in the reference stream. Relative activities of selected extracellular enzyme activities suggested that the biofilm in the reference stream was nutrient-limited. Nutrient-releasing substrates placed beneath wood veneers indicated co-limitation of nitrogen and phosphorus on biofilms in the reference stream,and nutrient limitation may have been responsible for low microbial respiration, fungal biomass, and extracellular enzyme activity on wood in the reference stream. Our results indicate that competition for nutrients by microbial biofilms may play a regulatory role in detrital processing in these streams.

Laboratory feeding studies using TALLAPERLA sp., a common macroinvertebrate shredder, were conducted to explore the suitability of wood biofilms as a food resource for shredders. There were no differences in TALLAPERLA growth rates on wood and leaves, and TALLAPERLA grew equally well on wood incubated for 1 or 2 months. TALLAPERLA nymphs were not food-limited and fungal production was able to compensate for invertebrate grazing. In the absence of leaf litter, stream shredders such as TALLAPERLA can survive and grow on the microbial biofilm on wood.