Multiple stressors in watersheds

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Watersheds are exposed to a variety of contaminants, as well as both natural and anthropogenic stressors that can interact to cause adverse effects in fish and other organisms. Contaminants also normally enter watersheds as complex mixtures, with differing composition and properties that greatly influence their environmental fate, bioavailability and toxicity (ecotoxicology). Our current lack of understanding of these interactions creates considerable uncertainty when assessing environmental risk of various human activities, especially when multiple stressors are considered across watersheds. The current research program is working toward a better understanding of contaminant effects and interactions in watersheds, and the development of predictive cumulative effects frameworks that consider multiple stressors in the context of natural variability. In our past studies it has been shown that municipal wastewaters contain a large variety of chemicals that have the potential to alter physiology, metabolism and endocrine function in fish. In the Grand River watershed, wild rainbow darter (Etheostoma caeruleum) exposed to wastewater discharges caused changes across all levels of biological organization (molecular to populations). Unfortunately making linkages between specific contaminants in the environment and effects in wild fish is hampered by our poor understanding of how these diverse chemicals interact during early development to cause adverse outcomes in fish. This proposal is focused on applying controlled lab exposures of rainbow darter (eggs to adult) to specific chemicals suspected of causing effects in fish though different mechanisms (ethynylestradiol, triclosan, metformin) and contrasted to wastewater effluents (complex mixture). It will test the ability of these chemicals individually and as a mixture to cause (possibly potentiate) a variety of key changes in physiology and reproduction, including gene expression, gonad development (including intersex), sex steroid production, and behaviour. We will compliment this research with the development of a fate and effects model utilizing a decade of chemical exposure and effects data on fish in the Grand River, and the responses to recent changes in effluent quality. Finally we will initiate studies of the environmental risk of the emerging threat of novel functionalized nanoparticles (nanomedicines) that are also expected to be released into wastewater systems in the near future. The research will therefore continue to advance our understanding of important mechanisms and processes currently limiting the ability of national and international agencies to assess and manage the uncertainty and risk of this diversity of contaminants being released into our watersheds.