Harmful blooms of the toxic dinoflagellate Ostreopsis cf. ovata have been a recurrent phenomenon along the Mediterranean rocky coasts in the last decades. Since their first records, there has been a widespread belief that the extension of this dinoflagellate well-known in tropical areas to higher latitudes was due to the global warming and the general rise of seawater temperature. Blooms of Ostreopsis cf. ovata along the Conero Riviera (northern Adriatic Sea) occur between the end of the summer and the beginning of the autumn since 2006. Ostreopsis cf. ovata abundance data collected from its first record to nowadays were analyzed to better define the interannual trend of this phenomenon and its possible linking to certain climate change predictors. A significant increasing trend in the magnitude of Ostreopsis phenomenon was observed up to year 2012, then a stabilization at relatively low values was observed. This trend does not follow the incessant increase in water temperature observed during the last three decades in Adriatic Sea, but rather recalls that of an invasive species, although the provenience of O. cf. ovata in the Mediterranean Sea is still unresolved. Even if the Ostreopsis bloom in this area seems to slightly lessen in the last decade, Ostreopsis abundances still reach values up to 103 cells cm-2 which could be harmful to human health.
Accoroni et al. (Fri,) studied this question.