Toxicity and toxin profile of the dinoflagellate Alexandrium tamiyavanichii and toxic mussels in Harima-Nada of Seto Inland sea, Japan

Abstract

From October to November 2004, the paralytic shellfish poison (PSP)-producing dinoflagellate Alexandrium tamiyavanichii was observed at Harima-Nada, Seto Inland Sea at a maximum cell density of 4,960 cells/L. The wild cells of the dinoflagellate collected from the same seawaters, and cultured cells derived from them showed toxicity scores of 6.25-15.4 × 10 -4 and 2.7-3.5 × 10-4 MU/cell, respectively, both of which were much higher than those of previously reported strains. PSP of the wild cells was mainly composed of gonyautoxin (GTX) 5 (40.6-52.4 mol%) and GTX4 (15.6-24.8 mol%), showing a unique composition that was greatly different from those of the previously reported strains, or of the cultured cells, whose main toxin component was GTX3 (average 37.6 mol%). The mussel Mytilus galloprovincialis collected from the same area in the same period accumulated a relatively high level of PSP (13-28 MU/g), suggesting a risk that A. tamiyavanichii may induce high-level PSP contamination of bivalves even at a cell density as low as around 5,000 cells/L.