Species of the planktonic diatom genus Pseudo-nitzschia of the Pacific coasts of Mexico

Species of the diatom genus Pseudo-nitzschia are common in the marine phytoplankton world-wide. Some species of this genus have been proved to be source of domoic acid (DA), a powerful toxin causing Amnesic Shellfish Poisoning (ASP) in humans and probably mass mortality in sea birds and mammals. Net plankton samples obtained during several cruises and seasons from the Pacific coasts of Mexico: western coasts of Baja California, Gulf of California, coasts of the tropical Pacific of Mexico (including the Gulf of Tehuantepec), were analyzed to study the species of the diatom genus Pseudo-nitzschia. Four species ( P. australis, a presumed toxic species, P. fraudulenta, P. lineola, P. pungens) and one former species of the genus, Nitzschia americana were recorded and studied by light and electron microscopy. The most common species was P. pungens, widely distributed along the Pacific coasts of Mexico. All other species appeared occasionally and in low relative abundances. The probable misidentification of P. australis as P. seriata is discussed, as well as the presence of another potentially toxic species, P. delicatissima, in the Gulf of California. No case of toxicity (ASP) has been fully documented and therefore related to toxic Pseudo-nitzschia species in the Gulf of California. This revised version was published online in July 2006 with corrections to the Cover Date.