a species of diatom
Usually Pyrodinium bahamense var compressum a causative organism for paralytic shellfish poisoning. Other species includes Alexandrium sp., Chatonella marina, Prorocentrum minimum, Pseudo-nitzschia sp. and Cochlodinium polykrikoides.
Domoic acid poisoning, the term used when referring to marine mammals and seabirds that are poisoned, is called amnesic shellfish poisoning (ASP) when humans are involved. Domoic acid is produced naturally by at least 15 species of the pennate diatom genus Pseudo-nitzschia, found around the world. This toxic phytoplankton (a type of microscopic algae) is filtered from the seawater by molluscan shellfish (mussels, oysters, clams, etc.) during their normal feeding. The domoic acid concentrated in this way can then be transferred to consumers, including humans, if the toxic shellfish are eaten. Governments monitor for the presence of domoic acid and prevent the harvesting and sale of any toxic shellfish. No cases of ASP have occurred since the original episode in 1987.