Toxicological characterisation of the aqueous soluble phase of the Prestige fuel-oil using the sea-urchin embryo bioassay

The soluble components of fuel oil are generally assumed to be the fraction that is toxic for organisms living in the water column. We have used a liquid phase bioassay with embryos of sea urchin to assess the toxicity of the water-soluble fraction (elutriate) of the fuel oil spilled when the tanker Prestige sank on 13 November 2002. Two methodologies to obtain elutriates were carried out in order to compare the effect of the extraction method on the measured toxicity. Analyses of Σ16PAHs (naphthalene, acenaphtylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, Indeno(1,2,3-c-d)pyrene, benzo(a)pyrene, dibenz(a,h)anthracene and benzo(ghi)perylene) and four metals (copper, cadmium, lead and zinc) were conducted and linked to the biological response. The effective concentration that provoked a delay in the successful embryogenesis of 50% of population (EC 50 ) was 2.3% of fuel oil. No differences in final toxicity between the two elutriation treatments were found, although the rotated extraction seemed to be more effective than magnetic stirring in transferring contaminants from the fuel oil to the water. Toxicity was mainly associated with the low-weight PAHs (2–4 benzene rings).