Pseudo-nitzschia is a new genus of pennate diatom derived from the genus Nitzschia due to its chain-forming colony. This diatom is capable of producing neurotoxin domoic acid (DA) which responsible for amnesic shellfish poisoning (ASP). First case of ASP was reported in Prince Edward Island Canada in 1987 involving 3 human fatalities. Symptoms of DA intoxication include nausea, seizure and loss of short-term memory. Currently there are more than 30 species of Pseudo-nitzschia, with almost half of them are toxic. Some species confined to temperate of tropical water while some are cosmopolites. They inhabit mostly in estuarine area and the open sea.