Assessing exposure of small-bodied fish to experimental crude oil spills in contained shoreline environments using biliary polycyclic aromatic compound metabolites

Abstract

Knowledge gaps pertaining to the remediation of freshwater lakes impacted by oil spills have persisted despite recent record highs for oil production and transportation across vulnerable regions in North America. The multiyear Freshwater Oil Spill Remediation Study (FOReSt), conducted at the IISD-Experimental Lakes Area in Canada, is focusing on the efficacy of minimally invasive methods for remediating oil spills in freshwater boreal lakes. In this thesis, the impacts and remediation of diluted bitumen (dilbit) and conventional heavy crude oil (CHV) spills were investigated (year 1), as were a variety of different remediation methods for spills of dilbit on different shoreline substrates (year 2). Two common small-bodied fish, fathead minnows (Promephales promelas) and finescale dace (Chrosomus neogaeus), were used to assess exposure to petrogenic polycyclic aromatic compounds (PACs) in model enclosed shoreline ecosystems impacted by spills and remediated using minimally invasive techniques. Short-term exposure to PACs, the most toxicologically relevant compounds in oil, was assessed in fish using biliary metabolite concentrations. In year one, finescale dace and fathead minnows residing in oil treated enclosures each had biliary pyrene metabolite concentrations that were positively correlated with pyrene concentrations in the water of the enclosures. Three months after the initial spills, fish in the enclosure receiving dilbit were significantly more exposed to PACs than fish in reference enclosures that did not receive oil. In year two, both finescale dace and fathead minnows residing in oil-treated exposures, regardless of shoreline substrate, showed increased exposure to PACs compared to fish in reference enclosures and the pristine lake environment two and a half months after the spills. No significant differences in exposure were observed among the remediation treatments. Biliary PAC metabolite concentrations were positively predicted by parent PAC concentrations in periphyton. PACs in periphyton two and a half months after oil introduction were positively correlated with PACs in the enclosures one week after spills, suggesting fish also had increased exposure to periphyton-bound alkyl-PACs. This thesis validates the use of small-bodied fish in assessing PAC exposure following freshwater oil spills and demonstrates the difficulties in estimating exposure using environmental concentrations in natural systems.