Wednesday, August 8, 2007 - 10:30 AMCOS 74-8: Methodologies for characterizing aquatic health can be used to monitor recovery in watersheds affected by mines
Aïda M. Farag, United States Geological Survey and Susan E. Finger, United States Geological Survey.
Mining activities can have physical (e.g. sedimentation) and chemical impacts on aquatic resources. Therefore, robust methods are needed to determine the impacts of physical versus chemical stressors. Population level effects (measured by survival), effects on biomass/density, and effects at the level of the individual (physiological endpoints) should be used in combination to assess the aquatic health in watersheds. This multifaceted approach can be used to monitor the success of recovery or remediation efforts, and redirect those efforts should they prove inappropriate. We have refined techniques for this approach in the Clark Fork River, Montana, Coeur d’Alène River, Idaho , Prichard Creek, Idaho, and the Boulder River, Montana watersheds in the western United States . Efforts in the Boulder River watershed provide one example of a successful integrated approach to characterizing aquatic health. Pathways of exposure were assessed by determining trace-element concentrations in water, sediment, biofilm, benthic macroinvertebrates, and fish tissues. Instream cage experiments at sites that had no resident trout indicated that elevated concentrations of cadmium, copper, and zinc were associated with increased mortality as well as hypertrophy (swelling), degeneration (dying), and necrosis of epithelial cells in gills of hatchery trout. In sites further downstream, the health of resident trout was impaired. A decrease in the number of trout per acre indicated population-level effects. Increased metallothionein, increased products of lipid peroxidation, and elevated concentrations of trace elements in fish tissues indicated individual-level effects. These data provide a comprehensive approach to documenting impacts; developing restoration goals; and documenting the success of remediation efforts.