THE STREAM ENVIRONMENT 181 



greatly modified macroinvertebrate species composition (Appala- 

 ciiian Regional Commission, 1969; Roback and Richardson, 1969; 

 Dills and Rogers, 1974; Herricks and Cairns, 1974). 



Herricks and Cairns (1974) studied macroinvertebrate communi- 

 ties at locations above and below acid mine drainage in Pennsylvania 

 streams (Table 1). Control stations v^^ere dominated by ephemerop- 

 terans, plecopterans, and odonates; dipterans (mainly chironomids) 

 and Hydropsyche were the common organisms at a station receiving 

 acid mine drainage. 



In an Alabama stream an isopod (Lirceus) comprised 43% of the 

 benthos at unpolluted stations, whereas acid stations were dominated 

 by chironomids, ceratopogonids and megalopterans (Dills and 

 Rogers, 1974). Reduced density and diversity were reported for 

 polluted stations (Table 1). 



These eastern studies contrast sharply with our study of Trout 

 Creek. Despite the fact that coal strip mining began about 30 years 

 ago and is presently being conducted along the creek, macroinverte- 

 brate communities adjacent to and below the mine spoils indicated 

 no discernible detrimental effect from mining activities. The number 

 of taxa was similar above, adjacent to, and below the mine. Standing 

 crop increased rather than decreased downstream, and taxonomic 

 composition was remarkably similar throughout the stream section 

 studied. Shannon— Weaver index values gave no indication of a 

 stressed macroinvertebrate community at any of the sites on Trout 

 Creek. 



Chemical Conditions and Macroinvertebrates 



Wentz (1974), referring to the effects of mine drainage on the 

 water quality of streams in Colorado, indicated that "approximately 

 450 miles (724 kilometers) of streams in 25 different areas are 

 adversely affected by metal-mine drainage. Coal-mine drainage is not 

 a problem, apparently because of the low sulfur content of Colorado 

 coal." 



Table 2 compares the water quality of Trout Creek with criteria 

 for acid mine drainage. In streams in western energy-development 

 areas, acidity is typically undetectable, and pH values generally range 

 from 6.5 to 8.5, with over 85% of all pH values falling between 7.0 

 and 8.0 (Skogerboe, 1976). Stream waters are well buffered, and 

 major inputs of acid or base would be required to shift the pH one or 

 more units. The chemoautotrophic bacteria, which greatly speed the 

 production of sulfuric acid and ferric hydroxide, are effective only at 

 low pH, whereas bacteria that oxidize ferrous iron at higher pH are 

 relatively unimportant in acid formation (Wentz, 1974). 



