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<br />DATA ANALYSIS <br /> <br />Interpretation of the health and integrity of the aquatic ecosystem was based <br />on a number of aquatic macro invertebrate indices and life history characteristics <br />of individual taxa and physical habitat and water chemistry data (if collected). <br />The indices used were those recommended for use by the u.s. Environmental <br />Protection Agency (82) and others (43, 44, 45, 50,53, 79). These indices should <br />be compared to those calculated for other sites, either impacted or non-impacted, <br />and be used to document changes over time at the same site. Abundance data is <br />shown as the number per square meter (#/m^2) for quantitative samples and the <br />number per sample for qualitative samples. <br /> <br />Community summary statistics <br /> <br />Richness and enumeration measures <br />Taxa richness - Richness is a component and estimate of community structure and <br />stream health based on the number of distinct taxa. Taxa richness normally <br />decreases with decreasing water quality (50). In some situations organic <br />enrichment resulta in an increase in the number of taxa, including EPT taxa (82). <br /> <br />Abundance - The abundance of aquatic macroinvertebrates is an indicator of habitat <br />availability, suitability and fish food abundance. It may be reduced or increased <br />depending on the type of pollution. <br /> <br />EPT - A summary of the taxa richness within the insect orders Ephemeroptera, <br />Plecoptera, and Trichoptera (EPT). These orders are considered to be sensitive <br />to pollution. EPT generally increases with increasing water quality (53). <br /> <br />Family level measures - All families are separated and counted. The number and <br />diversity of families normally decreases with decreasing water quality (50). <br /> <br />Diversitv measures <br />Ecological diversity is a measure of community structure defined by the <br />relationship between the number of distinct taxa (S) and their relative <br />abundances (n). Washington (83) reviewed the use of diversity indices in aquatic <br />ecosystems and suggested the use of Simpson's D, however, Shannon's index is widely <br />used and dbar has been used by the EPA (85) and the USFS (84). <br /> <br />Margalef's <br />of species <br />today (83) <br />was used. <br /> <br />index - Based on the presumed linear relationship between the number <br />and the logarithm of the number of individuals. It is seldom used <br />and is included for comparison to historical data where this index <br />It is calculated as S-l/ln(n). <br /> <br />Menhinick's index - This index is correlated <br />used in aquatic ecology (83) and is included <br />historical data where this index was used. <br /> <br />to sample size and is not widely <br />primarily for comparison to <br />It is calculated as S/SQRT(n). <br /> <br />Shannon's H - Shannon's H' (47) is widely used in community ecology. It is a <br />measure of the average degree of uncertainty in predicting what species an <br />individual chosen at random from a collection of species and individuals will <br />belong. This average uncertainty increases as the number of species increases <br />and as the distribution of individuals among taxa becomes even. The higher the <br />number the greater the diversity. However, small cold streams have naturally low <br />diversity and for this reason some have criticized the use of H'. <br /> <br />Dbar - Dbar has been used by the EPA (85) and the USFS (84). Values range from <br />o to 3.32 log N. It was calculated based on the machine formula presented by <br /> <br />Lloyd et al. (86). <br />