The toxic effects of oil sands contaminants on fish
Ecotoxicology , Fish , Sublethal effects , Behaviour , Field study , Mesocosms
Extracting bitumen from the Canadian oil sands is a water-intensive process that produces large volumes of oil sands process-affected water (OSPW). The recycling of OSPW for bitumen extraction causes it to become highly contaminated with salts, metals, residual bitumen, and dissolved organic compounds called naphthenic acid fraction components (NAFCs). Currently, large volumes of OSPW are being stored in temporary settling basins called tailings ponds. As OSPW is known to be toxic to a variety of organisms, there is increasing concern about accidental breaching and leaking of OSPW from tailings ponds into the environment. To mitigate these risks, there are plans for controlled releases of treated OSPW into surrounding environments. More information on the sub-lethal effects of OSPW, and particularly NAFCs derived from OSPW, is needed to inform regulations that will protect wildlife and human populations living downstream of the oil sands region. Our studies evaluated whether exposure to NAFCs extracted from OSPW has lethal and sub-lethal effects on fish. Our first study exposed fathead minnow (Pimephales promelas) embryos to environmentally relevant concentrations of NAFCs (2 - 54 mg/L) for 7 days, then raised surviving larvae in outdoor mesocosms of clean lake water for 1 month. We found that embryonic exposure to NAFCs resulted in decreased embryo survival and impaired development, with persistent adverse effects on larval fish survival and behaviour after one month of rearing in lake water. Our second study exposed juvenile yellow perch (Perca flavescens) to environmentally relevant concentrations of NAFCs for 7 days and monitored the fish for changes in behaviour before and after NAFC addition. We found that juvenile exposure to NAFCs (15 mg/L) impaired fish survival, fish equilibrium while swimming, and antipredator behaviour in fish. Our findings show that NAFCs have both lethal and sub-lethal effects on fish development and behaviour that could affect their survival and performance following exposure. These findings are pertinent for developing evidence-informed decisions regarding planned OSPW releases in the Canadian oil sands region.