Invertebrate metal accumulation and toxicity from sediments affected by the Mount Polley mine disaster

On August 4, 2014, a tailings dam failed at the Mount Polley copper and gold mine near Likely, British Columbia, Canada, releasing approximately 25 M m[Formula: see text] of contaminated water and solid tailings material into Polley and Quesnel lakes. Water, sediment, freshwater scuds (Hyalella azteca), and mayfly larvae (Ephemeroptera) were collected during the summer of 2018 from Polley Lake, affected and unaffected sites in Quesnel Lake, and both mine-contaminated and clean far-field sites as references. Analytical results indicated that invertebrates from sites affected by the tailings breach had elevated metal concentrations relative to those from non-affected or reference sites. We conducted a controlled laboratory exposure to determine if laboratory-reared Hyalella azteca metal concentrations were related to field-collected water or sediments from the same sites as the field study. Half of the replicates prevented amphipods from directly contacting sediments (water-only exposure), while the other half allowed them direct access (sediment and water exposure). Whole-body Cu concentration was highest in Hyalella exposed to substrate from the most contaminated sites as well as in treatments where they were allowed direct access to sediments. Hyalella having direct access to metal-contaminated sediments showed reduced survival and growth relative to those in reference or control treatments. These results suggest that metals from the fine sediments associated with the Mount Polley mine disaster are bioavailable and potentially toxic to epibenthic invertebrates, even several years after the initial breach.