Effects of acid mine drainage on a Southwestern Pennsylvania stream

Physicochemical parameters and benthic macroinvertebrate community structure were studied in a small valley stream in southwestern Pennsylvania. Sampling stations were located upstream and downstream of coal mine drainage input. Due to an alkaline discharge and significant downstream alkalinity the pH below the mine effluent remained between 5.8 and 7.0 throughout the course of this 18 mo study. The major factor affecting the benthic community seemed to be ferric hydroxide deposition. Certain taxa (Plecoptera and Ephemeroptera) were abundant at station sites above the mine discharge, while only those taxa tolerant of polluted conditions, such as Chironomidae and Tubifex, were prevalent at the downstream station sites. An analysis of benthic populations through changes in total numbers, species diversity, and species indicator organisms graphically demonstrated environmental stress within this aquatic ecosystem.