Book excerpt: Four sample sites from within the Otter Run Watershed (Lycoming County, Pennsylvania) were examined to obtain both qualitative data (taxonomic richness) and quantitative data (numbers of invertebrates) on aquatic insect communities in areas affected by acid mine drainage (AMD) and subsequent chemical amelioration. All the sites had similar pH values, but the site most affected by AMD had the lowest taxonomic richness, diversity, and population sizes.