Two-decade study on toxic outbreaks in the mediterranean sea

Across the Mediterranean basin, toxic outbreaks due to harmful algal blooms have been spreading with an ever increasing incidence over the past decades. Such toxic events have been particularly monitored and studied across the Northern Adriatic Sea, where mollusk consumers have experienced recurring sanitary problems, and shellfish farmers suffered heavy economic losses. Our study, carried out over the past 20 years, has afforded significant insights into the problem of marine biotoxins infesting the Adriatic Sea, that shows a pretty unique, complex, and continuously changing toxin profile. In the late ‘80s we afforded the first experimental evidence over the occurrence of a marine biotoxin in the Adriatic Sea, by isolating and characterizing okadaic acid (OA). Since then through the mid ‘90s, OA and some of its analogues have been the main Adriatic marine biotoxins. From 1995 on yessotoxin (YTX) and its analogues have played a dominant role in Adriatic mussel poisoning, while OA has slowly subsided until virtually disappearing around the turn of the new millennium. A number of new YTX analogues have been isolated from Adriatic mussels and chemically characterized by our research group.1 In particular, around the beginning of the 3rd millennium, desulfocarboxyYTXs have proven the most abundant toxic compounds detected in Adriatic mollusks. Because of the strong difference in harmfulness between OA (a potent tumor promoter) and YTXs (with no significant oral toxicity), the EU set up a new protocol for separating these toxins in two distinct layers. However, detection of the new desulfocarboxyYTXs, co-extracted in the same layer as OA, requires an urgent revision of the official protocol. In addition, over the last years spirolides have become the main Adriatic toxins posing serious health risks to seafood consumers. To make the picture even more complex, also domoic acid has recently entered the Adriatic toxin profile. Even though detected so far at concentrations lying below its regulatory limit, this latter toxin must be attentively monitored as it could any time be rising at alarming levels. Besides all of the above hazards, over the past years another most dangerous threat has been impending over the Mediterranean Sea: the spreading of the tropical alga O. ovata, responsible of a human intoxication characterized by respiratory distress and conjunctivitis. Our investigation on Mediterranean O. ovata has brought to light the presence of a new palytoxin-like compound, we named ovatoxin-a, alongside minor amounts of a putative palytoxin; both toxins can be considered responsible for human intoxications.