Abstract

Alexandrium catenella (Whedon & Kofoid) Balech, a dinoflagellate known as a potential producer of Paralytic Shellfish Poisoning (PSP), is reported for the first time from a new geographical area of the Mediterranean Sea (Sardinia, Italy). Till now, the distribution of A. catenella over the Mediterranean had been limited to Spain and possibly France together with recent, associated events of PSP-toxicity in shellfish. Specimens of A. catenella detected in summer 1999 in Sardinia (Gulf of Olbia) exhibited cell size and pattern of thecal plates comparable with those described from other localities, being mostly observed in two to four-celled chains. Despite the existence in literature of some descriptions of this species as a coldwater organism, in Sardinia the environmental scenario during the occurrence of A. catenella was typical of the warm season (water temperature: 26 °C), consistent with recent observations from the Catalan coast. The finding of A. catenella in the Gulf of Olbia (Tyrrhenian Sea) – a restricted, eutrophic area holding a commercial harbour and an intensive activity of mussel farming – suggests a possible introduction of this species through either the ballast waters discharged from foreign ships or the importtrade of shellfish from other countries. The lack of any previous evidence of this dinoflagellate in stations of the gulf monitored on a routine basis since 1992 further supports the non-indigenous character of A. catenella in the affected Tyrrhenian area and its transport from other localities via the above-mentioned means of dispersal. The potential for future bloom events, spreading over new Italian areas and possible constraints to the sustainable development of coastal areas must be considered.

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