Assessing accumulation and biliary excretion of naphthenic acids in yellow perch exposed to oil sands-affected waters

Naphthenic acids are known to be the most prevalent group of organic compounds in oil sands tailings-associated waters. Yellow perch (Perca flavescens) were exposed for four months to oil sands-influenced waters in two experimental systems located on an oil sands lease 30km north of Fort McMurray Alberta: the Demonstration Pond, containing oil sands tailings capped with natural surface water, and the South Bison Pond, integrating lean oil sands. Yellow perch were also sampled from three lakes: Mildred Lake that receives water from the Athabasca River, Sucker Lake, at the edge of oil sands extraction activity, and Kimowin Lake, a distant reference site. Naphthenic acids were measured in perch muscle tissue using gas chromatography-mass spectrometry (GC-MS). Bile metabolites were measured by GC-MS techniques and by high performance liquid chromatography (HPLC) with fluorescence detection at phenanthrene wavelengths. A method was developed using liquid chromatography-high resolution mass spectrometry (LC-HRMS) to evaluate naphthenic acids in bile. Tissue analysis did not show a pattern of naphthenic acids accumulation in muscle tissue consistent with known concentrations in exposed waters. Bile fluorescence and LC-HRMS methods were capable of statistically distinguishing samples originating from oil sands-influenced waters versus reference lakes. Although the GC-MS and HPLC fluorescence methods were correlated, there were no significant correlations of these methods and the LC-HRMS method. In yellow perch, naphthenic acids from oil sands sources do not concentrate in tissue at a measurable amount and are excreted through a biliary route. LC-HRMS was shown to be a highly sensitive, selective and promising technique as an indicator of exposure of biota to oil sands-derived naphthenic acids.