The toxic effects of oil sands contaminants on fish
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Date
Authors
Reynolds, Jessie
Keyword
Ecotoxicology , Fish , Sublethal effects , Behaviour , Field study , Mesocosms
Abstract
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.