Stream aufwuchs accumulation: Disturbance frequency and stress resistance and resilience.

This study explored the influence of copper disturbance frequency in model stream ecosystems on: stream Aufwuchs biomass accumulation, Aufwuchs stress resistance and resilience, diatom diversity, and species composition. Duplicate experiments were conducted in which four streams were subjected to four different copper dosing regimes (frequencies): continuously, once daily, every third day, and no dose. After ten days of the initial dosing regimes, each stream received an additional copper twenty-four-hour disturbance. Resistance and resilience to the additional disturbance were greater in streams dosed with copper either continuously or once daily. In contrast, diatom species number, diatom diversity, and accumulations of extractible adenosine triphosphate and chlorophyll a were greater in streams dosed either every thrid day or not at all. In addition, stress resistance was inversely related to community age.