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 shortterm and long term (e.g., watershed revegetation) strategies to promote ecosystem recovery in such situations.
Using a reference-condition comparison, recovery of benthic invertebrate communities from acidification was assessed in three lakes in Killarney Wilderness Park approximately 40-60 km from the massive metal smelters in Sudbury, Canada. Test site analyses (TSAs) were used to compare the park lakes to 20 reference lakes near Dorset Ontario, 200 km to the east. An extension of a previous survey (1997-2001) of two sensitive mayfly species (Stenonema femoratum and Stenacron interpunctatum) was conducted in one of the lakes. TSA results indicate that the three Killarney lakes remain significantly different from reference condition due primarily to higher abundances of a few acid-tolerant families and the presence of some less abundant sensitive families. Colonization rates differ greatly between the two mayfly species presumably because of competition for available habitat. Overall, this study suggests that early colonizers will gain an advantage to out-compete subsequent arrivals, and these competitive interactions will delay the return of communities to reference condition.
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