Using freshwater animals to understand trace element exposure in nature

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As a world leader in the mining and refining of metals such as copper and nickel, the onus is on Canada to also be a world leader in understanding and mitigating the environmental impacts of these contaminants. To explain and predict metal accumulation by aquatic animals one needs to consider the various forms in which metals occur in water, sediment and food as well as the behaviour of the organisms involved (feeding, burrowing, etc.). By measuring the way in which metals are distributed in animal cells, one can also predict the likelihood that these contaminants will cause toxic effects and be transferred to higher trophic levels. To understand and model such processes, my students and I consider: i) the geochemical forms (species) in which trace elements exist in water and sediment, ii) the burrowing and feeding behaviours of animals; iii) the distribution of trace elements in animal cells. We study trace elements such as cadmium, nickel and selenium that are likely to be present at high concentrations in Canadian ecosystems influenced by mining and fossil-fuel extraction. Previously, we demonstrated that in highly-acidic metal-impacted lakes, cadmium and nickel concentrations can be very high in lakewater but low in insects, whereas our recent measurements suggest that the opposite is the case for selenium. We plan to determine why this is the case. We will also measure the impacts of acidic, metal-contaminated, water flowing from abandoned mine sites by measuring spatial and temporal changes in metal concentrations in sentinel organisms, as well as the structure of aquatic communities living along the contamination gradient. In this regard, we will explain why closely related animals sharing the same habitat can differ so widely in their metal concentrations, as well as explaining how sentinel species survive at highly-contaminated sites. Overall, these research activities will allow us to refine the tools needed by environmental risk assessors to better understand, predict and mitigate the effects of trace elements, as well as permit the training of students who will be eminently qualified to take their places as a part of the next generation of environmental researchers.