Toxicity of orimulsion‐400® to early life stages of atlantic herring (Clupea harengus) and mummichog (Fundulus heteroclitus)

The toxicity of Orimulsion-400® (PDVSA-BITOR), an emulsion of 70% bitumen in 30% water, was tested during the embryonic development of Atlantic herring (Clupea harengus) and mummichog (Fundulus heteroclitus) in duplicate experiments. Air injection and different salinities were included in the herring assays to examine their effects on Orimulsion-400 toxicity. Water-accommodated fractions (WAFs) of no. 6 fuel oil were tested in the mummichog assays to compare Orimulsion-400 toxicity with that of a heavy fuel oil. Concentrations of Orimulsion-400 as low as 0.001% (v/v) were harmful to both species. In herring, the more sensitive of the two species, this concentration produced 100% abnormal larvae. Similar abnormalities, including pericardial edema and spinal deformities, the same signs of toxicity caused by heavy fuel oils and polycyclic aromatic hydrocarbons (PAHs), were produced in both herring and mummichog. Fish exposed to Orimulsion-400 also suffered from increased mortality, reduced heart rates, premature hatch, and reduced lengths compared to control fish. Orimulsion-400 was approximately 300-fold more toxic than the WAFs of no. 6 fuel oil. Salinity had few clear effects on Orimulsion-400 toxicity, but aeration of test solutions greatly reduced toxicity by causing bitumen to coalesce and float. Aeration also removed toxic chemicals such as PAHs. The present study suggests that in the event of a spill, Orimulsion-400 could impair fish recruitment, but that strong wave action would reduce toxicity by accelerating the removal of emulsified bitumen from the water column.