Toxicity assessment of Amphidinium carterae, Coolia cfr. monotis and Ostreopsis cfr. ovata (Dinophyta) isolated from the northern Ionian Sea (Mediterranean Sea)

► Distribution and toxicity of harmful microalgae of Ionian Sea have been assessed. ► Among these species, Ostreopsis cells exerted a toxic effect on sea urchin embryos. ► Algal cell lysate of each microalga inhibited the in vitro sea urchin development. ► Ostreopsis affected processes such as DNA replication and gene expression. ► Monitoring these microalgae is essential for their effects on marine recruitment.