Microcystin producing cyanobacterial communities in Amvrakikos Gulf (Mediterranean Sea, NW Greece) and toxin accumulation in mussels (Mytilus galloprovincialis)

► Mytilus galloprovincialis mussels from Amvrakikos Gulf found to be severely contaminated with hepatotoxin microcystin. ► The cyanobacterial community found to be dominated by the cosmopolitan species Synechococcus - Synechocystis. ► A potential microcystin synthetase (mcyS) gene fragment was cloned. ► This is the first report of the presence of microcystins in the Mediterranean Sea.