The Toxic Effects of Oil Sands Contaminants on Developing Amphibians
The Canadian oil sands contain a viscous form of crude oil known as bitumen. This research aimed to understand how contaminants from the oil sands industry can impact the growth and development of juvenile native amphibians. The extraction of bitumen contributes to the atmospheric deposition of metals and polycyclic aromatic compounds (PACs) to snowpack which may be released to aquatic ecosystems upon snowmelt. Furthermore, due to increases in Canadian bitumen production and demand, transport via pipeline has amplified across North America, increasing the probability of bitumen spills in freshwater ecosystems. Using a common native species, the wood frog (Lithobates sylvatica), the developmental effects of contaminated snowmelt (Chapter 2) and a simulated diluted bitumen spill (Chapter 3) were tested in two semi-natural mesocosm-based experiments. Wood frog embryos were exposed to six snowmelt samples collected from the Athabasca oil sands at different distances from industrial operations for a period of 25 days. In addition, free-swimming wood frog tadpoles were exposed to lake water contaminated with seven environmentally relevant concentrations of diluted bitumen for a period of 21 days. Wood frog embryos exposed to contaminated snowmelt sampled from within a 50 km radius of mining operations accumulated PACs, displayed the altered expression of metamorphosis associated genes, experienced reduced development, impaired growth, an increased frequency of malformations, altered behaviour and delayed effects on growth and development after the end of the exposure. Wood frog tadpoles exposed to lake water contaminated with diluted bitumen had no measured change in thyroid hormone tissue concentrations (T3 and T4) and cytochrome P450 activity or expression. In addition, diluted bitumen contaminated lake water had no effect on the growth, development, or survival of tadpoles during the exposure period. Overall, contaminated snowmelt may impair the normal growth and development of wood frogs inhabiting wetlands near oil sands mining operations. However, the dissolved fraction of contaminants following a diluted bitumen spill may not impact the normal growth and development of wood frogs, provided the spill is rapidly and effectively remediated.