Using macroinvertebrates to assess ecological integrity of streams remediated for acid mine drainage

Studies assessing stream restoration of acid mine drainage (AMD) usually use community metrics that emphasize only a few attributes of ecological integrity. We used a variety of measures to examine recovery of macroinvertebrate communities in a watershed receiving passive treatment for AMD. We measured density, richness, functional diversity (FD), taxonomic diversity (, a measure of taxonomic relatedness), and community taxonomic composition at 4 stream sites over an 11-year period: 1 reference not affected by AMD, 2 downstream of treatment systems, and 1 AMD-impacted site with no treatment. Our objectives were to determine if communities have responded to remediation, and examine whether FD and provided additional insights into ecology integrity. Richness, FD, and at the reference site were significantly higher than for other sites, but did not consistently differentiate treated and untreated sites. Additional information provided by FD and on attributes related to functional redundancy and taxonomic relatedness was self-evident given the simplicity of nonreference communities. Ordination of community composition incorporating knowledge of taxa autecologies indicated that treated sites were slightly less impacted than the untreated site, and trend analysis indicated slight improvement at 1 treated site. However, communities below treatment remained taxonomically distinct, with much lower densities than reference condition. Macroinvertebrate communities showed less recovery than was determined for benthic diatom communities at the same sites in a previous study. Several attributes of ecological integrity for different types of stream organisms should be incorporated into bioassessment of AMD restoration because they can vary in their response.