A standard ecotoxicological bioassay using early life stages of the marine fish

Fish tests must be developed for both regulatory and conservation reasons, as such testing forms an indispensable component of integrated toxicity testing strategy for the marine environment. To standardise a fish embryo test, the acute toxicity of metals and polycyclic aromatic hydrocarbons (PAHs) to early life stages (ELS) of turbot (Psetta maxima) was studied. Embryos were exposed to dilutions of cooper, cadmium, mercury, fluoranthene, phenanthrene, pyrene and naphthalene in darkness and under visible light. Hatching success, yolk sac alterations, pericardial edema, skeletal deformities and mortality were observed. The effective concentrations (EC50, EC10,) no observed effect concentration (NOEC) and the lowest observed effect concentration (LOEC) were determined at the end of the bioassays. Exposure to metals and PAHs in ecologically relevant concentrations, either in darkness or under artificial light, caused significant lethal and sublethal effects in turbot, such as alterations in yolk sac, pericardial edema and skeletal abnormalities. According to the 96 h EC50, the ranking of acute toxicity for metals was respectively: 47.4 (46.8–59.2) μg L−1 Cu; 51.5 (20.9–91.7) μg L−1 Cd, and 83.2 (62.3–125) μg L−1 Hg. For PAHs, acute toxicities were 5.2 (4.3–6) μg L−1 pyrene, 12.3 (6.4–12.7) μg L−1 fluoranthene, 52.2 (30.4–82.7) μg L−1 phenanthrene, and 142 (55–228) μg L−1 naphthalene. Pyrene was consistently the most toxic PAH. In addition, light exposures were performed and photo-enhanced toxicity was found only for fluoranthene and pyrene. Turbot embryos were found to be more tolerant to metals and PAHs than were hatched larvae. These results suggest that, considering the short duration of the ELS turbot test and its high sensitivity, it is suitable for use as a standard test for marine fish