Influence of Salinity on Copper Toxicity in Paracentrotus lividus and Arbacia lixula Embryos

The sea urchins Paracentrotus lividus and Arbacia lixula have a key role in benthic dynamics and they are often used to assess the toxicity of environmental contaminants. The aim of this research was to investigate the influence of salinity on copper toxicity on P. lividus and A. lixula embryos, evaluating the impact of future ocean salinity variations and estimating an optimum range for embryos. For this purpose, sea urchin embryos were exposed to different copper concentrations under varying salinity regimes, estimating the toxic effects with the percentage of abnormal embryos and the Integrative Toxicity Index (ITI). Results revealed acceptable levels of anomalies in a salinity range of 33–36‰ for A. lixula and 33–39‰ for P. lividus. The effect concentrations (EC50) of copper reveals increasing toxicity at increasing salinity for both sea urchin species, but between 33–36‰ (A. lixula) and 36–39‰ (P. lividus) the toxicity appear inversely related with salinity. This study illustrates the difficulty in relating a biological response to bioavailability, because the uptake and the sensitivity to copper across salinities is influenced by differences in osmoregulation, enhancing our knowledge about optimal salinity ranges and the potential impact of climate change on sea urchin embryo development.