Development of subcellular distribution methods to identify indirect or direct effects of metals on aquatic organisms

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In Canada, strict regulations control the composition of discharges from mining and smelting operations into aquatic environments. Mining companies are currently required to conduct environmental effects monitoring (EEM), which involves conducting biological studies in the aquatic environment to assess and monitor effects potentially caused by their effluent. Stantec Consulting Ltd. is engaged in the EEM studies required as part of the Metal Mining Effluent Regulations (MMER). Its investigations on various client mining sites, conducted downstream from the mine effluent and in reference areas unaffected by the effluent, have revealed that the aquatic communities in the receiving environment often differ from the communities present at the reference sites. Our proposed study is designed to provide a tool to determine if the observed effects are in fact due to waterborne/diet-borne metal exposure or rather to habitat differences. Reports in the scientific literature have demonstrated that exposure to metals in the environment may lead to metal accumulation and toxicity in fish and other aquatic species. Once metals enter living organisms, they can penetrate into their cells and cause deleterious effects. Alternately, the entering metals can be detoxified by binding to molecules designed to sequester them and prevent them from exerting their toxic effects. The first objective of this project is to investigate, with a better resolution than is currently available, to which intracellular ligands metals bind and to relate metal accumulation in specific fractions to toxicity. With this information in hand, the second objective is to develop a tool for environmental effects monitoring based on the subcellular metal partitioning technique that would provide a better estimate of risk of toxicity than the current approach of using total tissue metal accumulation in fish and other aquatic organisms. Finally, the project will also investigate the trophic transfer of metals through the aquatic food web. This research will contribute to advancing our understanding of the toxic modes of action of metals to aquatic organisms. It will also improve our capacity to monitor the risk for aquatic organisms of metal mining effluents.