Fate and Fathead Minnow Embryotoxicity of Weathering Crude Oil in a Pilot‐Scale Spill Tank

For several years now, the Natural Resources Canada (NRCan) research facility at CanmetENERGY Devon has been performing experiments in a pilot-scale spill tank using 1,200 L of river water to examine the physical and chemical behaviours of various crude oil/water mixtures under varying water temperature regimes. As oil toxicity can be modulated by weathering of the petroleum products, this study aimed to assess changes in fish embryotoxicity to mixed sweet blend (MSW) crude oil as it weathered at air and water temperatures of 14°C and 15°C respectively for 28 days. The physicochemical behaviour of the oil was also monitored. Water samples were taken from the spill tank five times during the 28-day experiment at days 1, 6, 14, 21, and 28 and were used to perform toxicity exposures using fathead minnow embryos (Pimephales promelas). For each water sampling day, newly fertilized embryos were exposed to a serial dilution of the spill tank water, non-contaminated river water (used in the spill tank), and a reconstituted water laboratory control. Embryos were raised until hatching. While mortality was not significantly altered by the oil contamination over the time period, malformation occurrence and severity showed concentration-dependent responses to all contaminated water collected. Data suggest that days 14, 21, and 28 were the most toxic time periods for the fish embryos, which corresponded to increasing concentrations of unidentified oxidized organic compounds detected by Q-TOF. This study highlights a novel area for oil research, which could help to better understand the toxicity associated with oil weathering for aquatic species. This article is protected by copyright. All rights reserved.