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COAL CREEK <br /> Four stations were sampled on this stream in April and June, 1989. <br /> When sampled in April , the aquatic macro invertebrate community at the <br /> upper Station (1) indicated that there was good water quality and some <br /> good instream substrate in the reach sampled. There were some indications <br /> of sediment and organic nutrients in this ecosystem. Cleanwater species <br /> present included the mayflies Pgggrils and hithrggeui, a stonefly, <br /> PQdmQ&", and a dipteran, ricarg. The observed number of shredders <br /> in the community is generally found where riparian habitat is in good to <br /> excellent condition. The diversity and resident population numbers for the <br /> taxa indicated there was good stability in this stream reach. <br /> At Stations 2, 3, and 4, there were indications of instability, and <br /> although Station 2 still had 23 taxa in the community, none )f them had <br /> resident population numbers, and conditions appeared to become more <br /> degraded in the downstream direction. The number of taxa in the community <br /> was reduced from 23 to eighteen at Station 3 and to twelve at Station 4, <br /> with none of the taxa having resident population numbers. There appeared <br /> to be a non—selective impact, possibly from chemicals used in the coal <br /> mining operation. <br /> The macro invertebrate biomass was reduced by 75% at the lower three <br /> stations compared to that found at the upper station, and the DAT <br /> Diversity Index values ranged from 13.7 to 5.6 from the upper to the lower <br /> station, respectively, indicated the severity of impacts in a downstream <br /> direction. Ordinarily, with most of the perturbations that occur in <br /> aquatic ecosystems, the more tolerant taxa flourish and can compete best <br /> under certain conditions while others diminish or disappear. In this case, <br /> it appeared that there was a non—selective impact, because all of the <br /> species were severely reduced in number. <br /> When sampled in June, it appeared that even the upper station had <br /> impacts from some type of perturbation. There were indications of sediment <br /> and organic nutrients in this ecosystem. Cleanwater species present <br /> indicated there was still fairly good water quality, but only two of the <br /> taxa had resident population numbers, ana those were some of the most <br /> tolerant species. Chironomids and Baetid mayflies were able to compete <br /> best under the existing conditions. This was true at each of the stations. <br /> Those two species dominated the communities, and other species had very <br /> few organisms in their populations. The observed low numbers of shredders <br /> in each of the communities are generally found where riparian habitat is <br /> in poor condition or where instream habitat quality is not suitable for <br /> those species. <br /> 30 <br />