Ostreopsis cf. ovata an emerging threat to human health in the Mediterranean basin: LC-HRMS-based approach for monitoring and risks mitigation strategies

The benthic marine dinoflagellate Ostreopsis cf. ovata, once confined to tropical and subtropical regions, since the end of 1990s has been wide spreading in temperate areas including the Mediterranean basin, with harmful algal blooms (HABs) increasing along Italian coastlines. Particularly, in the summer 2005 a massive proliferation of O. ovata along the Ligurian coasts of Genoa induced a toxic outbreak of alarming proportions with negative impact on marine environment and humans. During that toxic event, people who had spent time on or close to beaches, apparently just breathing marine aerosols, manifested a severe respiratory syndrome with symptoms including fever, respiratory distress, conjunctivitis with, in some cases, needs of hospitalization. The chemical agents responsible for toxicity were identified by liquid chromatography coupled to mass spectrometry (LC-MS) and LC-high-resolution MS (LC-HRMS) studies conducted by MarBioTox research group and were named ovatoxins (OVTXs)¹, structural congeners of palytoxin (PLTX), one of the most potent non-protein marine toxins known to date. Since 2005, MarBioTox group has kept on investigating the Ostreospis phenomena that become recurrent during summer-autumn in the Mediterranean area being responsible for numerous human poisonings following inhalation of toxic aerosols, and skin contact, posing serious concerns to human health also related to a possible ingestion of contaminated seafood. Consequently, the European Food Safety Authority (EFSA) in 2009, announced the need to optimize efficient analytical methods for OVTXs and PLTXs detection. Currently, LC-HRMS is the best analytical strategy to detect OVTXs in different matrices (algae, seawater, seafood) and, over the time, it allowed to bring to light different toxin profiles for Mediterranean strains of O. cf. ovata mostly dominated by OVTX-a followed by OVTX-b, OVTX-d and -e isomers, OVTX-c and isobaric PLTX.²

The Italian Ministry of Health solicited the introduction of surveys actions to manage risks associated to O. cf. ovata blooms, defining a three-phase monitoring plan: routine, alert and emergency phases, identified by thresholds of cells concentrations in the water. In the alert phase (cell density 10,000-30,000 cell/L) an assessment of the extension of the affected area and health surveillance are required, while the emergency phase (cell density >30,000 cells/L) represents the favoring conditions for aerosol and spray formation and chemical analysis of toxins in water is requested.³ As a result, new and timely early monitoring methods of alert had to be found. Solid Phase Adsorption Toxin Tracking technology represents a viable and sustainable method that can passively adsorb toxins produced by harmful microalgae and dissolved in water.⁴ This method offers several advantages over current monitoring techniques: it provides reliable, sensitive, and time-integrated sampling of various aquatic toxins and also has the potential to provide an early warning system for the presence of toxic microalgae and the possible bioaccumulation of these toxins in food.

¹ P. Ciminiello, C. Dell’Aversano, E. Fattorusso, M. Forino, L. Tartaglione, C. Grillo, N. Melchiorre, J. Am. Soc. Spectrom., 2008, 19, 1, 111–120

² L. Tartaglione, E. Dello Iacovo, A. Mazzeo, S. Casabianca, P. Ciminiello, A. Penna, C. Dell’Aversano, Environ. Sci. Technol., 2017, 51, 13920−13928

³ E. Funari, M. Manganelli, E. Testai, Harmful Algae, 50, 2015, 45–56

⁴ M. McCarthy, F. N.A.M. van Pelt, V. Bane, J. O'Halloran, A. Furey, (2014), Toxicon, 89, 77-86