A comparison between oyster (Crassostrea gigas) and sea urchin (Paracentrotus lividus) larval bioassays for toxicological studies

The respective sensitivity of oyster (Crassostrea gigas) and sea urchin (Paracentrotus lividus) embryos and larvae to salinity, and to various micropollutants (four heavy metals, three pesticides) and to two polluted sediments were compared with a simplified bioassay method. C. gigas embryos and larvae were more sensitive to copper; the sensitivity of both species to tributyltin (TBT) was practically the same; P. lividus was more sensitive to lead and mercury. The only pesticide found to be toxic was a herbicide, Dinoterbe, to which oyster larvae were more sensitive than sea urchin plutei. Of the two sediments tested, the first one had effects on P. lividus embryogenesis only; C. gigas embryos and larvae were more affected by the second sediment which was originated from a harbour and was polluted by heavy-metals. The choice of species for biomonitoring may be based on biological considerations, such as the availability of mature adults for obtaining gametes, or on the salinity of the studied area; the oyster bioassay seems to be more suitable for coastal and estuarine brackish waters, because of the broader salinity tolerance of estuarine bivalve larvae as compared to sea urchin larvae.