Alexandrium fundyense is a dinoflagellate. It produces toxins that induce paralytic shellfish poisoning (PSP), and is a common cause of red tide. A. fundyense regularly forms massive blooms along the northeastern coasts of the United States and Canada (;, resulting in enormous economic losses and public health concerns. Enzyme electrophoretic data and RNA genetic analysis show Alexandrium fundyense and A. tamarense to be closely related, while mating compatibilities even suggest them to be varieties of a single heterothallic species.