Characterizing the effects of chronic conventional heavy crude oil exposure on the growth, development, and behaviour of larval wood frog (Lithobates sylvaticus)

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Date
2025-01-03
Authors
Scott, Adam
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In recent years, the need for data on the effects of oil spills on freshwater environments has become increasingly important in Canada. This thesis will address some of these gaps by focusing on the ecological impact of oil spills on amphibians, specifically wood frog (Lithobates sylvaticus) tadpoles, within the context of two major research studies: the Freshwater Oil Spill Remediation Study (FOReSt) and the Floating Wetland Treatments to Enhance Remediation (FloWTER) study which took place at the International Institute for Sustainable Development Experimental Lakes Area (IISD-ELA) in Northwestern Ontario. The FOReSt study aimed to assess the effectiveness of non-invasive oil spill remediation techniques in shoreline habitats, while the FloWTER study investigated the potential use of symbiotic plant-microbe systems via engineered floating wetlands for the degradation of oil-derived hydrocarbons. FOReSt simulated an oil spill event and industry-standard remediation response (shoreline rinsing), characterizing the fate and bioaccumulation of oil components in tadpoles exposed to weathered conventional heavy crude oil (CHV) in shoreline enclosures. Results indicated significant bioaccumulation of total polycyclic aromatic compounds (tPACs) in tadpole tissue, though no measurable effects on growth, development, or survival were observed. Qualitative histological analysis of hepatic tissues found no significant differences between treatment and control groups, suggesting that tadpoles did not experience adverse health impacts under the conditions of the study. The amphibian component within the mesocosm tanks explored the chronic exposure of wood frog tadpoles to a water-accommodated fraction of CHV in combination with floating wetland treatments. Behavioural assays and histological evaluations were conducted to determine the impact of these oil spill response techniques on tadpole health and behaviour. The results showed no significant differences in bioaccumulation, growth, development, or behavioural metrics, such as total distance travelled, or time spent near conspecifics. These findings suggest that the amphibian early life stages studied were resilient to the oil spill scenarios tested under the conditions and remediation methods applied. Further research is needed to fully understand the long-term impacts of oil spills on amphibian populations and freshwater ecosystems.

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Oil, Amphibians, Freshwater, Wood Frog
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