Toxic response of two Mediterranean crustaceans species to oil dispersants

Many million metric tons of crude and refined oil enter the environment each year as a result of anthropogenic sources such as oil spills. Dispersant products are designed to reduce the damages on marine ecosystem when an oil spill occurs. In the framework of a recent project funded by the Italian Ministry of the Environment (TAXA project), toxicity bioassays on native Mediterranean marine organisms have been standardized to assess oil dispersant toxicity. Preliminarily, acute toxicity tests with two marine crustaceans belonging to different taxa, Tigriopus fulvus (Copepoda) and Balanus amphitrite (Cirripedia), have been carried out with two commercially available oil dispersants and using SDS (Sodium Dodecyl Sulfate) as reference toxic compound. Larval stages were obtained from laboratory reared adults and two end-points (immobilization and mortality) were investigated after 24 and 48 h of exposition to compounds. Bioassays were repeated three times with different batches, timing and operators to check the test repeatability. The values of acute toxicity (LC50) on larval stages (II stage nauplii B. Amphitrite and I-II stage nauplii T. fulvus) have been compared. From the comparison of median lethal concentration values (LC50) obtained with larvae of the two organisms considered in this study, it showed that T. fulvus and B. amphitrite have a similar sensitivity and they both could be relevant organisms to evaluate the toxic effects of oil dispersant commercial products in Mediterranean sea.