Wood frogs (Lithobates sylvaticus) and their wetland breeding habitats are being intensively monitored in the oil sands region to assess the effects of environmental change on these valued ecosystem components. Spatial and temporal patterns of contaminants in the wetland breeding habitats and the wood frogs, and wetland physico-chemical characteristics are being examined to evaluate wetland health in the oil sands region. Wood frogs are studied because they are abundant across the study region and their life cycle includes aquatic and terrestrial stages. Parameters being examined include general water chemistry, amphibian population biology, and levels of total mercury (THg) and other metals and organic contaminants such as polycyclic aromatic hydrocarbons (PAHs) and naphthenic acids in breeding pond water and amphibian tissues. Levels of PAHs were measured in water, tissue, and semipermeable membrane devices (SPMDs). THg in water ranged from 0.34 to 21.3 ng/L, did not exceed CCME safe limits for the protection of aquatic life at any of the 21 study sites, and did not vary significantly within or across years. THg was significantly lower in recently metamorphosed wood frogs compared to adults or tadpoles. Across all sites, THg in tissues ranged from below detection limits to 0.41 µg/g dw. Linear mixed models indicated that variations in the concentration of THg in water and frog tissues were not related to distance from upgraders, while preliminary data suggests that PAHs, particularly alkylated PAHs, accumulated to a greater extent in SPMDs located within the vicinity of upgraders (<25 km).
Bruce Pauli‘s research on the effects of environmental pollution have the overarching goal of establishing techniques that can be used to evaluate and assess environmental change. His research focuses on aquatic ecosystems using amphibian species as sentinel organisms. This research has included efforts to standardize toxicity tests with native amphibian species, to examine determinants of disease in native amphibians, and attempts to further understand cumulative effects and the response of wild amphibian populations to multiple stressors. Bruce Pauli is currently a Research Manager and Chief, Ecosystem Health Research Section within the Ecotoxicology and Wildlife Health Division of Environment Canada.