Potassium cyanide (KCN), a highly water soluble and bioaccumulative cyanide salt, is examined to determine the toxic effects by using two green algae (Dunaliella viridis, Nannochloropsis oculata) and genetically different two sea urchin (Paracentrotus lividus, Arbacia lixula) species. To determine the toxic effects on the early developmental stages of sea urchin embryos, 72-hour embryotoxicity studies were conducted. Potassium cyanide toxicity at cellular level was also investigated and 6-hour embryos of both sea urchin species were used to determine genotoxic effects of KCN. Since plutei naturally feed on microalgae, two species of plankton were used to reveal phytotoxic effects of KCN. KCN was found to be embryo- geno- and phytotoxic. EC₅₀'s for P. lividus and A. lixula were found 7.96 and 6.52 μM. IC₅₀'s for N. oculata for 48 h and 72 h were found 23.66 and 80.45 μM. IC₅₀'s for D. viridis for 48 h and 72 h were found 14.31 and 23.36 μM.

The widespread use of rare earth elements (REEs) in a number of technological applications raises unanswered questions related to REE-associated adverse effects. We have previously reported on the multiple impact of some REEs on the early life stages of the sea urchin Paracentrotus lividus. The present investigation was to evaluate REE toxicity to early life stages in two unrelated sea urchin species, Sphaerechinus granularis and Arbacia lixula. The comparative toxicities were tested of seven REEs, namely yttrium, lanthanum, cerium, neodymium, samarium, europium and gadolinium as chloride salts at concentrations ranging from 10⁻⁷ to 10⁻⁴ M. The evaluated endpoints included developmental defects and cytogenetic anomalies in REE-exposed embryos/larvae, and decreased fertilization success and offspring damage following sperm exposure. The results showed different toxicity patterns for individual REEs that varied according to test species and to treatment protocol, thus showing toxicity scaling for the different REEs. Further, the observed effects were compared with those reported for P. lividus either following embryo or sperm exposures. S. granularis showed a significantly higher sensitivity both compared to A. lixula and to P. lividus. This study provides clear-cut evidence for distinct toxicity patterns among a series of REEs. The differences in species sensitivity at micromolar REE levels may warrant investigations on species susceptibility to impacts along polluted coasts.