Influence of synthetic and biogenic surfactants on the toxicity of water-soluble fractions of hydrocarbons in sea water determined with the bioluminescence inhibition test

The influence of increasing amounts of surfactants on the toxicity of hydrocarbons was determined using the bioluminescence inhibition test (Microtox test). Three biogenic and three synthetic surfactants were tested against the water-soluble fractions (WSF) of crude and weathered Ekofisk oil, phenol, and naphthalene. Surfactant concentrations below 100 mg litre(-1) lowered the toxicity of the WSF, indicating an antagonistic interaction reducing the toxicities of surfactants and hydrocarbons. At concentrations greater than 100 mg litre(-1) the toxicity rose again and was higher than the untreated WSF. The point of reversal seemed to be the critical micelle concentration, at which the formation of oil/water emulsions is possible.