Influence of Acid Mine Drainage, and Its Remediation, on Lakewater Quality and Benthic Invertebrate Communities

Abstract

The abandoned Aldermac Mine in Québec, Canada, has been a source of acid mine drainage to Lake Arnoux since 1946. Restoration of the site was undertaken in 2008 and completed in 2010. We compared lakewater chemistry and benthic invertebrate communities in the spring of 2010, prior to complete restoration, and in spring 2011, when acid mine drainage was no longer entering the lake. Between these years, lakewater pH increased by about one unit and the concentrations of many trace metals declined substantially. In 2010, benthic taxonomic richness increased significantly with distance from the source of contamination, whereas after restoration, there was no longer a clear trend. Communities in highly contaminated stations tended to be dominated by burrowing taxa such as larvae of Chironomus (Chironomidae) and Oligochaeta, whereas less contaminated stations had taxonomic and functional communities that were more diverse. In the year following recovery, some new taxa appeared (Trichoptera, Odonata, and the Ceratopogonidae Bezzia), whereas the populations of an acid-tolerant Chironomus species declined. However, only larger individuals exhibited a significant response to pH and metal contamination.

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