The Effects of Disturbance Time Interval on Algal Biomass in a Small Idaho Stream

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An experiment was designed to test the potential effect that disturbance frequency may have on benthic algal accumulation in a stream ecosystem. The stream was divided into segments. After measuring algal biomass in each segment, the stream substrate was left undisturbed, or physically disturbed once or twice per month. The highest levels of algal biomass were found in the segments that had the short between-disturbance intervals. Intervals may have been short enough to allow r-selected algal species to re-colonize, flourish and maximize biomass potential. Possible explanations for these results may be an increase in nutrient availability by the removal of senescent or competitor algal cells and the change to a disturbance-resistant community, or a release from invertebrate grazing as disturbance frequency increased.

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