Spatial and temporal distribution of shredders in leaf-limited intermittent streams

Lotic invertebrate distribution patterns are governed by factors acting at scales ranging from regional or catchment-wide processes to characteristics of individual local patches (MALMQVIST 2002). Benthic assemblages in intermittent streams are subject to further constraints through the recurrent dry phase oftheir habitats (BouLTON & LAKE 1990). As macroinvertebrates are involved in various processes in stream ecosystems (WALLACE & WEBSTER 1996), their distribution patterns may affect ecosystem functions. Decomposition of organic matter is a crucial ecosystem process, recycling nutrients and supporting detrital based food webs. The significance of fragmentation of coarse organic matter by the functional feeding group shredders is well recognized (ANDERSON & SEDELL 1979, WALLACE & WEBSTER 1996, GRACA 200 l). The aim of this study was to investigate the spatial and temporal distribution of shredders in 3 intermittent streams. We hypothesized that shredder diversity and abundance would be highest at sites with (l) a shorter duration of summer drought, and (2) forest riparian vegetation; and that (3) recovery of shredders after summer drought would be slower at sites with longer dry phase.