Variability of toxin profile and content of Ostreopsis cf. ovata from the Mediterranean Sea

Blooms of Ostreopsis spp. once confined to tropical and subtropical areas have recently spread to more temperate regions such as the Mediterranean and the Southern-Atlantic coasts of Europe. In the last decade, O. confronta (cf.) ovata has become increasingly frequent with massive blooms with consequent relevant negative impacts on benthic communities and on human health through skin contact and toxic aerosols. Following the Mediterranean Ostreopsis-related outbreaks we developed a liquid chromatography-high resolution mass spectrometry (HRMS) method to be employed in the investigation of both field and cultured algal samples of O. cf. ovata. Our studies characterized O. cf. ovata as the producer of minute amounts of a putative palytoxin, one of the most potent marine toxins so far known, and of much higher amounts of several palytoxin congeners, that we named ovatoxins. Ovatoxin-a has been recently isolated and structurally elucidated, while ovatoxin-b, -c, -d, -e, and -f have not been isolated yet. Our recent research has been focused on characterization of toxin profiles of O. cf. ovata of different geographical origin that resulted to be quite different both qualitatively and quantivatively. We analyzed by LC-HRMS over 40 cultured strains of Ostreopsis cf. ovata collected along the Italian and the French Mediterranean coasts identifying basically 4 kinds of toxin profiles. In most of the strains ovatoxin-a dominates toxin profiles accounting for more than 50% of the total toxin content. But about 20% of the strains were found to produce only ovatoxin-a, d/e and putative palytoxin. Unique toxin profiles were found in a strain from Ancona (Marche, Italy) in which ovatoxin-f was the dominant toxin and a strain from Villefranche sur Mer (France) that did not produce ovatoxin-a, but just ovatoxin-b and c. These data trigger some questions on the reasons why toxin profiles and toxin content are so different as well as on toxins that need to be determined in monitoring programs of O. cf. ovata toxins in environmental and seafood sample.