Year of Publication: 2014
Abstract:
The oil sands landscape in northern Alberta is interspersed with large tailings ponds that hold wastewater from bitumen mining and extraction processes. Recent monitoring results indicate that annually many thousands of birds, mostly migrating waterfowl, land on the ponds associated with this industry, but very few appear to die because of that contact. Mortalities are typically associated with bitumen exposure, which coats bird feathers to prevent flight, flotation, and thermoregulation. The recent awareness that many birds land creates an urgent need to understand the sublethal effects of contact with other pond constituents such as naphthenic acids, polycyclic aromatic hydrocarbons, and metals. In this thesis, I reviewed the toxicological effects on birds of exposure to oil sands process-affected water and inferred potential toxicities of untested effects using a broader literature. There are few descriptions in the peer-reviewed literature of these effects, but some studies suggest that exposure to it causes reproductive disorders, alterations in endocrine and immune function, and changes in growth, metabolism, and population structure. To address the paucity of studies on waterfowl, I conducted a field experiment to emulate the repeated, short-term exposures to process-affected water that migrating water birds might experience in the oil sands. Pekin ducks (Anas platyrhynchos domestica) were exposed to recycled process-affected water without visible bitumen. Each exposure consisted of placing an individual bird in a plastic tub containing approximately 15 L of either process-affected water or tap water (controls) for 6–8 hours. Birds were exposed three times as juveniles and six times as adults. I assessed toxicity by evaluating body mass and a suite of biochemical, endocrinological, and hematological analytes as well as metal residues in the birds. Results provided little evidence of toxicity. Relative to controls, juvenile birds exposed to process-affected water had higher potassium, and lower bicarbonate and cholesterol following the final exposure period, and juvenile males had a higher thyroid hormone ratio (T3/T4). Adult birds exposed to process-affected water had higher levels of vanadium and lower gamma-glutamyl transferase, and, following the final exposure period, higher bicarbonate. Adult female treated birds had higher bile acid, globulin, and molybdenum levels, whereas adult males exhibited higher levels of corticosterone. However, even for the analytes that differed significantly, means were within standard reference intervals for birds, suggesting the absence of significant biological or toxicological effects. While it is premature to assume that ponds containing recycled water are not toxic to birds, the literature review combined with my own field experiment suggest that these ponds are substantially less dangerous than ponds containing bitumen and fresh tailings. More work will be needed to determine the generality of these results. However, for ponds that are not acutely lethal to birds and do not elicit chronic or sublethal effects, current deterrent efforts might be relaxed. This change would permit higher deterrent intensity at the more toxic ponds. This scenario contrasts with the current practices, which apply similar deterrent efforts across all types of process-affected ponds, potentially reducing, via habituation, bird protection from the constituents – bitumen and fresh tailings – that are most likely to cause mortality.
