The fathead minnow (Pimephales promelas) is a freshwater fish with a wide distribution in lakes, streams, and ponds across North America, including Ontario. This species has been recognized as one of the most useful model organisms for freshwater toxicology monitoring, due to its tolerance of its range for aquatic conditions. Synthetic estrogens are excreted as a metabolic product in the urinary waste of women using oral contraceptives. Estrogens are not effectively filtered out by sewage treatment plants and are subsequently released into water effluents, affecting aquatic wildlife. In response to experimentally heightened estrogen concentrations, male and female fathead minnows have shown increases in vitellogenin protein, and females have displayed delayed ovarian development and increased numbers of underdeveloped ovarian follicles. Males also experienced lowered gonadosmatic indices, and some males had primary stage oocytes in their testes. As would be expected, synthetic estrogen additions influenced fathead minnow reproductive success, leading to a collapse of the experimental fish population. By taking a multi-disciplinary approach, this study looks to identify how synthetic estrogens are threatening local fish populations, and how this may eventually disrupt the freshwater food chain. Collaboration with The Canadian Association on Water Quality (Kingston), Ravensview Wastewater Treatment Plant, and the Catarqui Region Conservation Authority will provide a greater understanding of the hormonal content in Kingston’s wastewaters. Ultimately, this study will provide more insight on the level of risk faced by freshwater fish populations on a local scale, and propose a method to reduce estrogen deposition in freshwater environments.
Chronic toxicity of oil sands tailings pond sediments to early life stages of fathead minnow (Pimephales promelas)
