Abstract
Blooms of more than 20 000 cells per litre of Dinophysis acuminata Claparède & Lachmann — a common dinoflagellate for at least the last decennium in the Dutch coastal area — were within three weeks related to cases of diarrhetic mussel poisoning in the Dutch Waddensea in 1976, 1979, and 1981. D. acuminata appeared to have produced a dinophysis toxin, which infested mussels for consumption.