New Ostreopsis species record along Cyprus coast: toxic effect and preliminary characterization of chemical-molecular aspects

The genus Ostreopsis E.J. Schmidt includes harmful benthic species that have been reported worldwide in both tropical and temperate regions. To date, genetic studies stated that Mediterranean Sea hosts two genotypes corresponding to the morphotypes of O. cf. ovata and O. cf. siamensis; moreover, a new genotype of Ostreopsis sp. was found along Greece and Cyprus coasts. Nowadays, reliable data on harmful algal bloom and cases of poisoning associated in the eastern Mediterranean basin are still scarce. This study describes, for the first time, toxic effects and chemical-molecular aspects of the Cypriot genotype of Ostreopsis sp. (C1036-2013). Ecotoxicological bioassays were performed exposing A. salina nauplii to the following treatments of Ostreopsis sp.: untreated culture, filtered and resuspended cells in fresh medium, resuspended and sonicated cells in fresh medium, growth medium devoid of algal cells by 6 μm (mucilage remains in the treatment) and 0.22 μm mesh size filtration. Our results show higher toxic effects (mortality and immobility) with the untreated Ostreopsis sp. culture (LC 50-48h = 45 cells/ml, EC 50-48h = 7 cells/ml). As regard lethal effects, the Cypriot strain seems to be less toxic than the most widespread species O. cf. ovata (LC 50-48h < 4 cells/ml), though further studies are needed to better understand the toxicity of this new genotype. Additionally, preliminary data on its toxic profile reports presence of new palytoxin-like compounds and the lack of palytoxin and all ovatoxins so far known, confirming the possibility of being considered a different species