Research Summaries > Impacts Domain |
DixonAll Canadian water quality guidelines for metals are based on single metals, despite the fact that aquatic organisms are invariably exposed to mixtures of metals. The approach most often used for environmental risk assessment at specific sites suspected of metal contamination is to assess the metals present individually. A unified approach that addresses the interactions of metals, for both uptake and impact, is one of the most pressing needs in metals' toxicology. This research will examine the interactions of waterborne and sediment derived metal mixtures to the aquatic invertebrate Hyalella azteca to develop relationships between water chemistry, toxicity and tissue residues. Development of relationships between sediment, waterborne and tissue metal concentrations should allow a solid estimate of bioavailability. Overall the work will allow metal speciation and uptake (pharmacokinetic) models to be linked for more meaningful and defensible metals risk assessment. Return to 2002 Domain Research Projects
Wood (top of page)Laboratory-based studies are being employed to understand and model the chronic impacts of Cd, Zn, and Cu on the health of fish in the wild exposed to these metals in the water, in the diet, and in combination. Particular emphasis is placed on the modifying effects of acclimation water chemistry (hardness, pH, metal levels, etc.), on the influence of diet quantity and quality (particularly ionic content), on lab-to-field validation of the results, and on endpoints useful for Biotic Ligand Modeling (e.g. tissue specific bioaccumulation, subcellular partitioning, physiological indicators of toxicity). In this context, we are first extending the current acute BLM's for waterborne Cu, Cd and Zn to the yellow perch (YP, Perca flavescens), a species endemic to the metal-impacted lakes of Rouyn-Noranda, Sudbury, and other sensitive areas on the Canadian Shield. The goal here is to bring our level of knowledge on the YP up to that on the rainbow trout (RBT, Oncorhynchus mykiss), the model species on which most patho-physiological and BLM development work has been performed to date. We are also examining the influence of acclimation and exposure history on the BLM characteristics, a key step in the development of chronic BLMs. Simultaneously, we are experimentally analyzing the complex interactions of dietary quantity and quality (calcium, NaC1, energy content) on the response of RBT to chronic metal exposures, in both the water and the diet. This issue is of great relevance in understanding trophic and bioenergetic responses in the field, as well as in the development of gastrointestinal BLMs, but has not been considered in previous studies. The results will contribute to both environmental regulatory strategies and market protection for metals, and strengthen our global and regional risk assessment framework for metals in the environment. Return to 2002 Domain Research Projects
Campbell (top of page)This field-based project is designed to test the prediction that relations between metal body burdens in indigenous fish and metal-induced effects at the organism and population levels will be improved if the metal body burdens are expressed not as total metal, but rather in terms of the metal's partitioning within particular target tissues. The key hypothesis to be tested is that there exists a mechanistic link between the intracellular speciation of the metals and the manifestation of deleterious effects at the organism and population levels. The overall objectives are thus (i) to determine whether metal <spillover> (Cd, Cu, Zn) consistently occurs in feral fish under conditions of chronic exposure to high ambient metal concentrations, (ii) to compare the following linkages: [A] chronic metal exposure metallothionein induction intracellular metal spillover endocrine/physiological impairment population-level effects, versus [B] chronic metal exposure impoverished benthic community bioenergetic effects population-level effects. Different life stages of yellow perch (Perca flavescens) have been chosen as trial biosentinel organisms. In Years 1 and 2 the main study area was centered around Rouyn-Noranda, in Northwestern Quebec; in Year 3 we initiated exploratory studies on lakes in the Sudbury area, and in Year 4 we will pursue this comparison of contamination, physiological and growth indices in the two areas. Return to 2002 Domain Research Projects
Chan (top of page)Our research seeks to determine where, and under what physico-chemical conditions, fish-eating wild birds in Canada are at risk for mercury (Hg) exposure sufficiently high to produce negative impacts on their health or reproductive success. Our field studies focus on environments affected by non-ferrous mining/smelting activities, and/or the presence of underlying geology high in Hg. Controlled dietary dosing studies are also being undertaken, to investigate the genotoxic and immunotoxic effects of methyl Hg exposure in birds, and to assess potential genetic and immunologic markers of elevated methyl Hg exposure in fish-eating wild birds. Another major focus of our research is to elucidate the metabolic interactions between Hg and Se, especially the biochemical role of Se in the demethylation of methyl Hg in tissues and eggs of Hg-exposed birds, and the nature of cellular Hg/Se/protein complexes. The proposed research will increase our ability to accurately predict the risks of Hg exposure in wildlife inhabiting different aquatic environments. Return to 2002 Domain Research Projects
Couture (top of page)Both field and laboratory studies will be carried out to examine the effects of environmental metal contamination on population structure and metabolic performance of wild yellow perch (YP; Perca flavescens) from the Sudbury area. Effects examined will include direct toxic effects as assessed by indicators of metabolic performance and oxidative damage , and their relationships to tissue metal concentrations and dietary metal uptake. Condition and metabolic performance in YP will also be related to indirect effects of food web disturbances investigated by C3 in the same lakes. Our study design will allow several laboratory-based models to be tested in wild populations of YP, and will extend work currently supported by MITE on YP populations inhabiting industrially contaminated lakes near Rouyn-Noranda, QC. Several lakes in the Sudbury area, which together provide a wide gradient of metal contamination including reference sites, will be sampled in spring and at the end of summer. Fish surveys will provide yellow perch population status and forage fish diversity. YP surveys will also include assessment of recruitment, reproductive fitness in adults, longevity, and condition. Gut contents, as a surrogate for YP diet, will be analyzed in terms of quantity (as a proportion of gut and fish weights) and quality (including ionic (Ca, Na) and metal (Cd, Cu, Ni and Zn) composition). These data will be used to identify relationships between environmental contamination—including diet—and tissue metal concentrations, aerobic and anaerobic capacities, tissue oxidative damage, growth, and condition. This field-based research is strongly linked to current MITE-RN aquatic effects research conducted by projects C2 and C3. By field validating laboratory-derived models, and by providing comparative data for Rouyn-Noranda studies, this project will improve the ecological risk assessment relevance of MITE-RN research activities. Ultimately, data from this study will strengthen the current ERA paradigm and improve environmental regulations that attempt to protect wild fish in metal-contaminated systems. |