HR: 1330h
AN: B33C-06    [Abstracts]
TI: Effects of Periodic Substrate Scouring on Scraper-Algae Interactions in a Small Idaho Stream.
AU: * Koetsier, P
EM: pkoet@boisestate.edu
AF: Dept of Biology, Boise State University, 1910 University Dr., Boise, ID 83725 United States
AB: Our objective was to examine how a stream benthic community would organize under periodic scouring events occurring at two different time intervals. We conducted our study in a small, 2nd ordered, mountain stream. We divided a series of stream segments into 3 treatment sections: 1) substrate was manually scoured twice a month, 2) the substrate was scoured once a month, and 3) the substrate was left undisturbed (control). We sampled algal biomass, benthic invertebrates and measured physiochemical variables (DO, water temperature, conductivity, pH, discharge) once every two weeks from June 1 to August 31. We found that scraping invertebrates (primarily Baetis, Cinygmula, Epeorus, Glossosoma) decreased with increased scouring, while algal biomass was positively related to scouring frequency. The algae recovered quickly between scouring intervals, the scraping invertebrates did not. By keeping scraper numbers low, scouring dampened grazing activity on the algae resulting in an increase in its biomass. Scouring may also have removed senescent algae, allowing metabolically active cells more access to nutrient, sunlight, etc.
DE: 9810 New fields (not classifiable under other headings)
SC: Biogeosciences [B]
MN: 2005 Joint Assembly