Assessment of sediment contamination by spermiotoxicity and embryotoxicitybioassays with sea urchins (Paracentrotus lividus) and oysters (Crassostrea gigas)

Gametes (sperm) and fertilized eggs (embryos) of the Mediterranean sea urch in, Paracentrotus lividus, and the Japanese oyster, Crassostrea gigas, were used to investigate the toxicity of two marine sediments, one polluted by polycyclic aromatic hydrocarbons (PAH) and the other by heavy metals. The s ediment samples were freeze-dried for storage, and three different treatmen ts were used for analysis: whole sediment, unfiltered elutriate, and filter ed elutriate. The two sediments were toxic to sea urchin spermatozoa but no t to oyster spermatozoa, and embryotoxicity was almost always the more sens itive endpoint for toxicity assessment. As a rule, whole sediment was more toxic than the elutriates by nearly two orders of magnitude. With respect t o embryotoxicity, the whole sediments and the elutriates of the PAH-contami nated sediment were more toxic to oyster embryos, whereas the elutriates of the sediment polluted by heavy metals had stronger effects on sea urchin e mbryos. The results confirm that bioassays with Japanese oyster embryos pro vide a more sensitive appraisal of toxicity in the marine environment than bioassays with other developmental stages. As a whole. Mediterranean sea ur chins and Japanese oysters were similar in overall sensitivity and are ther efore both equally suited as bioassay organisms, but tests with oysters are more reproducible because of the better performance of the controls.