Abstracts Geography

Early life stage development and biomarkers of polycyclic aromatic compound exposure in lake trout fry from a lake used to conduct model oil spills

by Cody Jackson

In the summers of 2018 and 2019, controlled and contained spills of diluted bitumen (dilbit) were introduced into enclosures installed in Lake 260 at the IISD-Experimental Lakes Area (IISD-ELA). These additions were performed to examine the fate and behavior of oil in freshwater systems and to compare the efficacy of selected cleanup techniques. The potential for impacts to early development of lake trout arising from exposure to residual oil was examined by comparing the health of early life stages of lake trout (Salvelinus namaycush) obtained from the lake where oil studies were conducted to those from three reference lakes. Eggs were collected from fish in the four study lakes (n = 3-7) and reared in both an in-situ and laboratory environment. Eggs that were reared in-situ were assessed for hatching success, with no significant differences being observed between lakes. In the laboratory, fish were reared until swim-up and a subsample of fry from each lake were evaluated for deformities, with no increase in deformity rates observed in the study lake, compared to fry originating from the reference lakes. Fertilization success, egg mortality, time to 50% hatch, hatching success and growth rates were also similar among lakes. We also evaluated PAC accumulation in unfertilized eggs as well as molecular and biochemical markers of PAC exposure in swim-up fry. Polycyclic aromatic compounds were detected in freshly spawned eggs, however concentrations were lowest in samples originating from Lake 260, indicating that the PACs were unlikely to be related to the dilbit additions to enclosures. Cytochrome P4501A (cyp1a) induction, as well as total glutathione concentrations and the ratio of its oxidized and reduced forms were measured in whole swim-up fry and levels were found to be similar between the study lakes. Results from this study indicate that the efficacy of containment and contingency measures from the 2018 and 2019 model oil spill studies at the IISD-ELA were effective. This research contributes to the growing body of literature examining the lower threshold of PAC toxicity in early life stage salmonids and highlights maternal transfer of PACs as a potential route of exposure in these fishes.