Theme Summary
Aquatic ecosystems are recognized to be sensitive to metal inputs, whether the metals enter via the atmosphere, as wet or dry deposition, or from the terrestrial catchment via diffuse surface runoff or point source effluents in the form of dissolved and particulate loadings. Because of this inherent sensitivity, environmental regulators and managers have tended to focus on the aquatic environment when assessing the environmental risks associated with metal extraction, refining, and use. However, all aquatic ecosystems are not equally sensitive to metal inputs. Methods used for regional or site-specific ecological risk assessments must take into account the characteristics of the receiving waters (e.g., pH, salinity, hardness, alkalinity, concentrations of organic matter and reduced sulphur species). Aquatic ecosystems also differ in their sensitivity to metal inputs for biological reasons, i.e. because of differences in their resident aquatic communities.
Research conducted under the Aquatic theme will focus on protecting the health of freshwater ecosystems, as their continued productivity is critical to recreational use of water, its direct consumption, and as a source of food. The goal of this theme is to provide a sound scientific basis for protecting the environment from metal contamination without unduly restricting human economic activities. Metals and metalloids being measured under this theme’s research program are: Cd, Co, Cu, Hg, Ni, Pb, Tl, Se and U.
The Aquatic Ecosystem theme contributions to the E & HHRA framework are:
A1: Provide important tools to industrial environmental managers, government regulators, and environmental scientists that will maximize the predictive power of metal toxicity models.
A2: Improve our ability to predict the effects of metals and metal mixtures.
A3: Develop tools to reduce the uncertainties associated with measuring the long-term impacts of mine effluents on a site-specific basis.
A4: Determine if current water quality criteria for the protection of aquatic life, based on water-only studies, are sufficiently protective of aquatic ecosystems where organisms obtain metals not just from water, but also from food and sediments; provide data for setting sediment quality guidelines.
At: Address the question of whether metal burdens attained from waterborne and diet-borne metals have similar effects on the consuming organism in order to explain and predict trends in metal concentrations and effects along food webs.
A6: Determine the concentrations and speciation of Se in the aquatic environment, specifically in Western Canada where mining activities and irrigation could contribute to Se loading, and relate these data to bioavailability.
A7: Identify sources of Se contamination to determine if Se burdens in waterfowl (in combination with other pollutants) are causing impaired reproduction and/or survival, and predict if this contamination could influence regional or continental populations.
Theme leaders are: Peter Campbell (INRS-ETE), and Uwe Borgmann (NWRI, Environment Canada). Research summaries and researcher contact information for the seven projects conducted under this theme may be viewed on the MITHE-SN web site here.
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