Grant: Strategic Projects - Group

Selenium (Se) is a priority pollutant in Canadian aquatic environments. It is an essential trace nutrient but represents an extreme toxicological hazard due to the very narrow range between essentiality and toxicity, especially in fish. Unlike other trace elements, exposure to and uptake of Se in aquatic systems occurs predominantly through the diet. It is transformed from inorganic to organic forms by microorganisms and can accumulate to toxic levels in higher trophic taxa. The complexity in the trophic transfer of Se in aquatic ecosystems has created much uncertainty and debate regarding its environmental risk assessment. Although federal monitoring regulations recently added Se to the list of substances to be monitored by industry in effluent and receiving aquatic environments, there remain significant research gaps that hamper objective assessment of its potential hazard to aquatic wildlife under site-specific conditions. Understanding of the key factors influencing Se cycling in Canadian aquatic environments will be critical for accurately assessing the toxicological risks to aquatic species, and thus, provide industries and regulators with better and more efficient tools to protect ecosystems without overly penalizing industries that release Se. The overall goal of this project is to develop an advanced, state-of-the-art risk assessment approach for Se in support of the Canadian resource industry's predictive modeling requirements. Using laboratory and field approaches key processes that govern the transformation and assimilation of Se, and its transfer along representative aquatic food chains will be researched. Also, the relative sensitivity of early life stages of native fish species that directly ingest this food base (i.e., biofilm), their sensitivity to Se resulting from maternal transfer of Se, and the associated underlying mechanisms of toxicity will be investigated. Based on these results we will develop an improved and field validated model for accurate and objective prediction of the exposure to dietary Se and its effects on native fish species. This will enable prediction of aquatic ecosystem responses of regulatory relevance based on mechanistic toxicity information across diverse fish species (adverse outcome pathways).