Occurrence of harmful algal species and shellfish toxicity in Sardinia (Italy)

Sardinia (Italy, north-western Mediterranean) is a commercially important producer of edible bivalve molluscs. Since the early 2000s, it was subjected to recurring cases of mussel farm closures due to toxic algal poison. Here, we present the studies on toxin concentrations and the associated potentially toxic phytoplankton distribution and abundances carried out by a regular monitoring programme in Sardinian shellfish areas, from January to May 2015. DSP toxins were detected in several bivalve molluscs samples, while PSP and ASP toxins were present just once, without exceeding the legal limits. Potentially toxic algal species have been constantly present. Pseudo-nitzschia species were often present during the entire study often with high abundances, while Dinophysis species reached high densities sporadically. Among PSP phytoplankton, only Alexandrium minutum Halim was found. The data obtained in this study showed an increase in the DSP toxicity in mussels in Sardinia. No clear relation between the occurrence of toxins in shellfish and the presence of toxic algal species was found, although a slight correlation between DSP toxins and Dinophysis species could be supported.