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AQUATIC ECOSYSTEM ANALYSIS <br /> FOR SELECTED STREAMS ON THE <br /> WHITE RIVER NATIONAL FOREST <br /> 1989 <br /> BACKGROUND AND METHODS <br /> In recent years land managers on many of our forests and BLM <br /> districts in the west have improved the stability and reliability of land <br /> management plans and decisions by sampling aquatic organisms which act as <br /> natural monitors of management activities within the drainages on public <br /> lands. <br /> During short-term exposure to water of poor quality or adverse <br /> changes in habitat, organisms that cannot tolerate the stress are <br /> destroyed and the aquatic macro invertebrate community structure changes. <br /> Since aquatic organisms respond to their total environment, they can <br /> become an effective tool for detection of environmental changes. <br /> Our analysis of aquatic ecosystems is based upon multiple factors <br /> including: <br /> 1. Various macroinvertebrate data - Community dry-weight <br /> biomass/sample expressed in gm/m2; number of individuals per taxa <br /> (resident populations?) ; DAT Diversity Index, which combines a measure of <br /> dominance and number of taxa; habit, habitat and feeding preferences of <br /> individual taxa or species ; specific tolerances of taxa; community <br /> composition; and BCI (Biotic Condition Index) , which indicates as a <br /> percentage how close an aquatic ecosystem is to its own potential. <br /> 2. Physical parameter data and <br /> 3. Water chemistry data <br /> Effective use of the Biotic Condition Index (BCI) depends upon the <br /> availability of data on stream gradient, natural capability of instream <br /> substrate (may not be the composition present if man-influenced <br /> sedimentation is found at the sample station) , total alkalinity, and <br /> sulfate in mg/l. <br /> Because of the way that macro invertebrates occupy space within a <br /> stream, it generally takes at least three samples to represent the <br /> 1 <br />