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Mid-Continent Resources'Stream Impairment Study 11 <br /> During high flow, the macroinvertebrate community at Station 1 reflected moderately <br /> tolerant and sediment tolerant animals such as Baetis and Chironomidae. During this time clean water <br /> species were found, however they were only present in small numbers. During the fall, the number <br /> of families increased by four from the spring. The EPT taxa, valued for increasing species diversity <br /> and their ability to reflect stress on an ecosystem through presence or absence, increased by five <br /> species. <br /> Sites 2 and 3 produced low species diversity during the high flow period and their BCI values <br /> of 15.5% and 16.3% respectively indicated poor stream ecosystem health. At low flow, species <br /> diversity increased at both sites with the addition of Ameletus oregotrerrsis, a moderately tolerant <br /> species, and Dipterans. Low flow BCI values also indicated that this system was in poor health. <br /> Site 4 showed signs of improvement in diversity from sites 2 and 3 during the spring with <br /> a Shannon-Weaver index of 2.50. The number of families increased four times from site 3. There <br /> was also a decrease in Chironomid populations and an increase in EPT taxa. In the fall, both the <br /> species diversity and the BCI dropped. The EPT taxa fell from 8 species to only one. There was a <br /> corresponding increase in Chironomidae populations. Lower dilution rates in the fall and calcium <br /> sulfate deposition may have been responsible for this decline. <br /> Site 5 reacted similarly to site 4 in seasonal patterns. In the spring, site 5 scored better than <br /> sitel in EPT taxa (9), Shannon-Weaver diversity (3.02) and a BCI value of 94.3% (the highest <br /> found). Clean water species such as Epeorus and Rhithrogeira were present but the dominant species <br /> were sediment tolerant Chironomids and Baetids. Low flow diversity decreased to 2.51, a reflection <br /> of the loss of 7 EPT taxa. There was an increase in Chironomids, Simulium, and Linurophora <br /> which are sediment tolerant species. Calcium sulfate precipitation may have caused a loss of habitat <br /> thereby affecting the presence of clean water species. <br /> Site 6 appeared to be the most constant site sampled during both flow regimes for species <br /> diversity and BCI values. BCI values implied excellent ecosystem health. Spring flows were <br /> conducive to the presence of Baetis bicaudalus. The Chironomids and Cirryg»rrila sp. which were <br /> present indicated heavy sediment loads during high flow. At low flow, community structure shifted <br /> as the Chironomids were reduced by 11% and the Plecoptera Taenionerrra sp. became the dominant <br /> species. <br /> At high flow, site 7 had a moderate species diversity of 2.85 and the BCI reflected excellent <br /> stream health at 94.0%. Baetis bicaudatus, Cinygmula sp. and the family Chironomidae were <br /> dominant as at site 6. During low flow, the BCI index at site 7 decreased 77.8% and indicated <br /> possible impacts not observed in the spring. Chironomidae populations increased by 18% and the loss <br /> of two EPT taxa reflected the drop in species diversity. <br /> Habitat Characterizatioirs. Habitat data are summarized in Appendix 5. In June, Site 1 <br /> ONMENUMW <br /> The SeaCrest Group <br />