RESUMEN
Our aim was to quantify impairment to invertebrate predator populations, particularly to Acroneuria sp. (Plecoptera, Perlidae), downstream of an acid mine drainage-impacted tributary to the North Fork of the Powell River, southwestern Virginia. Predatory insects comprised 9.0 +/- 1.3% of the total abundance at the three stations upstream of the impacted tributary, but were significantly reduced (p = 0.0039) downstream (3.9 +/- 0.6%). Acroneuria sp. populations followed the same trend, with the upstream average (2.3 and 2.8%) being significantly higher (p < 0.05) than the downstream averages (0.2 and 0%) during 1999 and 2000, respectively. Using correlation analysis, we evaluated the relationship between the percent abundance of Acroneuria sp. throughout this reach and metal concentrations in water, sediment, and biological tissues (invertebrate predators and primary consumers). Water column aluminum (Al) concentration was the only parameter that was significantly correlated with percent Acroneuria sp. abundance, with correlation coefficients of -0.845 and -0.873 during 1999 and 2000, respectively. While this correlation exists, it may not indicate a causal relationship, and experiments should be conducted to determine the long-term toxicity of various Al species to perlid stoneflies.