Abstract
The spatial distribution of the benthic invertebrate fauna of Konaiano Creek, a small, aseasonal, tropical mountain rainforest stream on Bougainville Island, Papua New Guinea, was studied for one year. Although the benthic fauna exhibited no pattern of temporal change, with all species undergoing continuous recruitment and growth, there was a clear pattern of spatial distribution with distinct, but intergrading communities in the waterfalls, riffles, runs and pools. Current speed and substrate particle size decrease progressively from the waterfalls (bedrock and boulders), to the riffles (boulders and cobbles), runs (cobbles and gravel) and pools (gravel and sand). The waterfalls and riffles exhibited the greatest density of fauna (mean abundance >13,000 animals/m2) and riffles had the greatest species richness, but equitability was highest in the runs and pools. All but two of 18 species examined showed significant preferences for particular habitats. The distribution of detritus within the stream and, to a lesser extent, the occurrence of spates, as well as flow regime, influenced the abundance of many of the less common taxa.