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Mid-Continent Resources'Stream Impairment Study 14 <br /> seemed to reflect a preponderance towards sediment tolerant species. In the spring, Station 1 <br /> showed effects from possible environmental factors that delayed production in the benthic <br /> community and resulted in lower numbers of animals than at the other stations. <br /> During low flow periods, faunal dynamics at some locations may be less controlled by <br /> natural factors as by influences from the mine drainages. Dilution was effective at eliminating <br /> toxicity of the mine drainage at Station 4 in the spring. However, in the fall, water collected at this <br /> station was toxic to Ceriodaphnia. At station 5, the water was not toxic to the ceriodaphs during <br /> either period, showing the effects of dilution from Dutch Creek on the mine drainage. Effects from <br /> the drainage on community structure could be seen during the fall in the benthic communities at <br /> Station 5. This was probably due to the fact that much of the flow at Station 5 during the fall was <br /> due to the contribution from the mine discharge. This was reflected in conductivity, hardness, <br /> alkalinity, sulfate, and temperature values that were only slightly lower than the values measured at <br /> Station 4. <br /> The Ceriodaphnia toxicity at Stations 2, 3, and 4 was likely the result of high alkalinity and <br /> sulfate levels. Chemical analyses detected no significant levels of either organic or inorganic <br /> contaminants at any of the sites in the basin. This would eliminate trace metals or hydrocarbon <br /> contaminants as possible sources of toxicity. Sediments consisting of coal fines and algal blooms of <br /> filamentous Cyanophytes were also common at these sites. <br /> Dominant taxa at these sites were highly tolerant species. Dipterans, especially midges of <br /> the Chironomidae family which characterized the site, display a wide range of tolerances to natural <br /> and anthropogenic stresses. These organisms are more resistant than most EPT taxa which can <br /> disappear during periods of stress. <br /> The alkalinity and sulfate levels had decreased by the time the mine drainage mixed with <br /> Dutch Creek at Station 5. This was reflected in a precipitate that formed along the banks of the <br /> drainage channel. The effects on benthic communities at Station 5 could be the result of several <br /> factors including sedimentation, high sulfate levels, and the formation of a calcium sulfate substrate <br /> which leads to a concretion-like effect in the sediments. This latter factor would contribute to a <br /> lower availability of acceptable habitat for benthic animals. The concretion was less evident during <br /> the spring which may mean that high flows either erode the material or have a higher capacity to <br /> absorb the high sulfate levels. <br /> The significance of the impacts from the mine drainage are difficult to assess. A significantly <br /> higher benthic biomass was present in the mine discharge channel, albeit composed primarily of stress <br /> tolerant species. Station 5, just below the discharge, had a benthic composition more closely <br /> resembling that of the other sampling stations, but overall numbers were reduced. It is not known <br /> whether this was due to a toxic effect from the discharge or from the effects of habitat impairment <br /> due to the precipitation of the calcium sulfate. Since no toxicity was measured with Ceriodaphiria, <br /> The SeaCrest Group <br />