Can natural variability trigger effects on fish and fish habitat as defined in Environment Canada's metal mining environmental effects monitoring program?
The Metal Mining Effluent Regulations (MMER) took effect in 2002 and require most metal mining operations in Canada to complete Environmental Effects Monitoring (EEM) programs. An “effect” under the MMER EEM program is considered any positive or negative statistically significant difference in fish population, fish usability, or benthic invertebrate community EEM‐defined endpoints. Two consecutive studies with the same statistically significant differences trigger more intensive monitoring, including the characterization of extent and magnitude and investigation of cause. Standard EEM study designs do not require multiple reference areas or pre‐exposure sampling, thus results and conclusions about mine effects are highly contingent upon the selection of a near perfect reference area and are at risk of falsely labelling natural variation as mine related “effects.” A case study was completed to characterize the natural variability in EEM‐defined endpoints during pre‐exposure/baseline conditions. This involved completing a typical EEM study in future reference and exposure lakes surrounding a proposed uranium mine in northern Saskatchewan, Canada. Moon Lake was sampled as the future exposure area as it is currently proposed to receive effluent from the uranium mine. Two reference areas were utilized: Slush Lake for both the fish population and benthic invertebrate community surveys and Lake C as a second reference area for the benthic invertebrate community survey. Moon Lake, Slush Lake, and Lake C are located in the same drainage basin in close proximity to one another. All three lakes contained similar water quality, fish communities, aquatic habitat, and a sediment composition largely comprised of fine‐textured particles. The fish population survey consisted of a non‐lethal northern pike (Esox lucius) and a lethal yellow perch (Perca flavescens) survey. A comparison of the five benthic invertebrate community effect endpoints, four non‐lethal northern pike population effect endpoints, and 10 lethal yellow perch effect endpoints resulted in the observation of several statistically significant differences at the future exposure area relative to the reference area(s). When the data from two reference areas assessed for the benthic invertebrate community survey were pooled, no significant differences in effect endpoints were observed. These results demonstrate weaknesses in the definition of an “effect” used by the MMER EEM program and in the use of a single reference area. Determination of the ecological significance of statistical differences identified as part of EEM programs conducted during the operational period should consider pre‐existing (background) natural variability between reference and exposure areas. Integr Environ Assess Manag © 2012 SETAC