engleski

Current problems and future research requirements for toxic algae in the central Adriatic

In response to favorable changes in their environment, certain algal species undergo a rapid population increase and may form visible patches on the surface reffered as the "red tide". These blooms may be either toxic or noxious, that is either producing specific toxins or causing anoxia through the decay process. Exeptional blooms of toxic phytoplankton species and their association with shellfish toxicity as the result of toxin accumulation in shellfish meat has been known for long time. Due to process of strong urbanization of coastal areas, inadeqate industrialization, tourism, intensive aqaculture and other anthropogenic influences provoking severe eutrophication, there is an increasing frequency, intensity, duration, and geographic spreading of outbreaks. Concern about toxic algal blooms has arisen in recent years becouse of their impact on public health, and on the economics of shellfish aqaculture. Poisoning by metabolites from marine algae has been classified into paralytic (PSP), neurotoxic (NSP) amnesic (ASP), and diarrheic (DSP) shellfish poisoning. The most important compounds of the DSP complex are okadaic acid (OA) and an increasing number of its derivatives named dinophysis toxins (DTX). Threath to public health has been aggravated by a recent discovey that OA is a highly selective inhibitor of protein phosphatases and a potent tumor promoting agent. Since phytoplankton toxins represents a serious threat to human health, as well to fish and shellfish farming, monitoring programs have been established in many countries. Investigation of the toxin structure, their biological function, and the biosynthetic pathway are also currently in progress. Kaštela bay is semienclosed bay, heavily polluted by land sources, both of domestic and industrial origin. Red tide events have been observed there regulary every summer since 1980, when it first occured in the Vranjic basin, the most threatened part of the Bay. Despite the presence of toxic algae (Gonyaulax polyedra and Alexandrium minutum) no toxic blooms has been recorded up to 1993, when the mouse bioassay analysis showed the presence of DSP toxins, thought in low concentration. Investigations have been carried out every summer since 1993, using the biological (mouse bioassay) and chemical (HPLC) methods. Preliminary studies in the Central Adriatic confirmed the presence of toxin producing species, thus implying the necessity of further investigations of the still unresolved questions. Due to lack of adequate equipment, we are not in the position to perform all necessary investigations, however we wish to highlight the existence of growing problem concerning the potential development of shellfish toxicity.

toxic algae; shellfish toxicity; okadaic acid; Central Adriatic; Phytoplankton toxins; DSP; PSP

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