Abstract
Acute lethal toxicity tests were conducted with young-of-the-year Mysis oculata exposed to oil-in-water dispersions (OWDs) and water-soluble fractions (WSFs) of Norman Wells crude oil. Median lethal concentrations (96-hour LC50s) are among the lowest reported for arctic marine crustaceans, ranging from 0.49-0.62 mgll for WSFs and 4.51-7.57 mgll for OWDs. Sublethal behavioral effects occurred at concentrations as low as 0.3 mg/l for WSFs and 1.5 mgll for OWDs. Adverse effects were caused primarily by the chemical toxicity of water-soluble hydrocarbons since there were no apparent physical effects due to dispersed oil droplets. OWDs were more toxic to mysids in sealed containers than in open ones. Median effective concentrations (96-hours EC50s) causing gross behavioral disturbances, moribundity and ‘ecological death’ suggest that high molecular weight volatile hydrocarbons found in OWDs are more toxic to mysids than low molecular weight volatiles present in WSFs. Due to its sensitivity, vulnerability, availability in nearshore waters, and ease of maintenance under laboratory conditions, M. oculata is recommended as a test organism for arctic marine toxicity testing and environmental monitoring.
