Delayed Recovery of Benthic Macroinvertebrate Communities in Junction Creek, Sudbury, Ontario, after the Diversion of Acid Mine Drainage

Restoration of streams impacted by acid mine drainage (AMD) often require extensive and expensive engineering solutions, but the long-term effectiveness of these treatments in terms of improving downstream biological communities, is rarely tested. A rather novel treatment for the elimination of AMD at a site on Junction Creek in Sudbury Canada, involved damming and diversion of AMD deep underground, with subsequent limestone treatment of the waters outside the watershed. We used a rapid bioassessment technique to assess the recovery of benthic macroinvertebrate communities in response to this diversion. Biological summary metrics including taxa richness, EPT (sum of Ephemeroptera, Plecoptera, Tricoptera) richness, Simpson diversity, as well as multivariate descriptors of relative taxa abundance were used to compare the test site to nine reference sites. There was rapid recolonization of many families of benthic invertebrates but the site remained significantly impaired 8 years after the diversion, with a particular scarcity of large sensitive organisms. Multiple factors, including drought events, delayed or set back recovery. This study indicated that ecological risk managers need to consider both short-term and long term (e.g., watershed revegetation) strategies to promote ecosystem recovery in such situations.