Assessing contamination baselines and contextualizing diluted bitumen effects in marine birds on Canada's Pacific Coast

Pacific Canada has a rich avifauna, however pipeline and port expansions, together with a growing human population will increase the quantity of petroleum used and potentially released into the marine environment. Birds are vulnerable to spilled oil, but research has not been synthesized since 1993. I reviewed the individual-level effects of crude oil and refined fuel exposure in avifauna with peer-reviewed articles to provide a critical synthesis of the state of the science and identify data gaps. One major gap was an absence of toxicity data for unconventional crude petroleum, such as oil sands bitumen that dominates Canadian production and will be delivered to the Port of Vancouver in increasing volumes. Breeding birds that become oiled may contaminate the shells of their eggs, and conventional crude oil can cause embryotoxicity at small quantities. To generate needed toxicity data in a sensitive early life stage, I conducted an egg oiling experiment with a major oil sands product, diluted bitumen (dilbit). Results indicated no detectable adverse physiological effects, although xenobiotic biotransformation gene expression and polycyclic aromatic compound (PAC) residue in the embryo confirmed that dilbit penetrates the eggshell and is absorbed by the embryo. Birds rapidly metabolize PACs in petroleum, and to date, oil pollution biomonitoring with invertebrates suitable for such contaminants has little overlap with marine wildlife hotspots. I surveyed oil pollution by measuring PACs and metals in bivalve mussels at bird breeding colonies. PACs were generally lower at remote sites than Vancouver Harbour, with the exception of Triangle Island, a Marine National Wildlife Area. However, the PAC data indicates that pollution sources are likely dominated by combustion rather than spilled petroleum. Measuring contaminant concentrations in tissue to infer whether effects are occurring in wildlife suffers from uncertainty. I studied relationships between whole embryo contaminant concentrations and mRNA transcript expression of toxicologically relevant genes in embryonic liver tissue from a Pacific Ocean seabird. I found several biologically plausible associations between contaminant concentrations and the expression of different genes, particularly for mercury. Accordingly, eggs routinely collected for biomonitoring programs could be used to relate chemical exposure to effects in free-living birds.