TOXICITY OF CRUDE-OIL TO THE MAYFLY, HEXAGENIA-BILINEATA (EPHEMEROPTERA, EPHEMERIDAE)

Effects of crude oil on survival and behavior of the mayfly Hexagenia bilineata were evaluated in laboratory studies. Mayfly nymphs were exp osed to the water soluble and oil residue fractions of crude oil. Mayf ly survival was not reduced by a 96-h exposure to either the water sol uble fraction or the oil residue mixed with sediment. However, signifi cant mortality did result from a 21-day exposure to oil residue mixed with sediment at concentrations as low as 500 mu g g(-1). Survival was also reduced after a 21-day exposure to oil-contaminated sediments (1 905 mu g g(-1)) collected 6 weeks after a crude oil spill in the Chari ton River, Missouri. In a behavioral test measuring habitat exclusion, organisms did noir avoid contact with sediment containing oil residue (50-800 mu g g(-1)). Collectively, results from these studies indicat e that exposure to oil residue in sediment will reduce survival of H. bilineata in the laboratory and may reduce survival in the environment for 6 weeks or more after an oil spill.