Methylmercury in fish: understanding effects and identifying approaches to decrease exposure

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During the past 200 years, humans have contaminated the surface of the Earth with mercury. When mercury reaches surface water (oceans, lakes, rivers), it can be transformed to methylmercury, which accumulates to high concentrations in fish and causes toxicity. Consumption of contaminated fish is the major way humans are exposed to methylmercury and it is detrimental to health. All provinces and territories in Canada, except Nunavut, have fish consumption advisories due to methylmercury. The first objective of this research will be to study the environmental processes that influence the transformation, or "methylation", of mercury to methylmercury. In British Columbia, we will study what determines how much mercury in the air is eventually available for methylation in lakes. In Quebec, we will study how the delivery of sulfate (acid rain) to lakes influences methylation. In Nunavut, we will study how the warming of lakes may actually cause some methylmercury to be transformed back to inorganic mercury. Ultimately, we wish to understand these processes well enough to be able to recommend management practices to reduce methylmercury concentrations in fish to the point that restrictions on consumption can be lifted. The second objective of this research will be to study the effects of methylmercury on the fish themselves. Fish are valuable resources, not only for humans but also intrinsically for ecosystems, and it wasn't known until fairly recently that methylmercury causes toxicity in fish, too. We will study how methylmercury affects the reproduction, growth, and survival of important fish species (walleyes, northern pike) in lakes of Quebec. This information will be useful for the proper regulation of sport and commercial fisheries that are contaminated with methylmercury.