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I" k <br /> v <br /> AQUATIC ECOSYSTEM ANALYSIS <br /> a FOR SELECTED,STREAMS ON THE <br /> WHITE RIVER NATIONAL FOREST <br /> s � <br /> 1990 <br /> .1 <br /> BACKGROUND AND METHODS <br /> In recent years, land managers on many of our forests and-BLM districts in the West have <br /> improved the stability and reliability of land management plans and decisions by sampling aquatic <br /> organisms, which act as natural monitors of management activities within the drainages on public lands. <br /> @� I. r .. <br /> �,_ During short-term exposure to watdr of poor quality or adverse changes in habitat,organisms that <br /> cannot tolerate the stress are destroyed and the aquatic macroinvertebrate community structure changes. <br /> :j Since aquatic organisms respond to their total environment, they can become an effective tool for <br /> detection of environmental changes. <br /> I <br /> Our analysis of aquatic ecosystems is based upon multiple factors, including: <br /> 1. Various macroinvertebrate data- Community dry-weight biomass/sample expressed in g/m2; <br /> number of individuals per taxa (resident populations); DAT diversity index, which combines a measure <br /> of dominance and number of taxa; habit, habitat, and feeding preferences of individual taxa or species; <br /> specific tolerances .of taxa; community composition; and BC1 (Biotic Condition Index), which indicates <br /> as a percentage how close an aquatic ecosystem is to i wn otential. <br /> 2. Physical parameter data, and <br /> 3. Water chemistry data. <br /> Effective use of the Biotic Condition Index (BCI) depends upon the availability of data on stream <br /> gradient, natural capability of instream substrate (may not be the composition present if in <br /> /ah-influenced <br /> -sedimentation is found at the sample station), total alkalinity, and sulfate in mg/l. <br /> Because of the way that macroinvertebrates occupy space within a stream, it generally takes at <br /> least three samples to represent the community accurately at a given station. One sample per station costs <br /> less but has little value for aquatic habitat assessment. One never knows if such single samples represent <br /> the best, the worst,or an average of possible conditions at the sampling site. Also as a side benefit, three <br /> 1 <br />