The occurrence of the toxic diatom genus Pseudo-nitzschia (Bacillariophyceae) on the West Coast of the USA, 1920–1996: a review

Abstract The known history of the genus Pseudo-nitzschia [mostly reported in error as Nitzschia seriata (PT. Cleve) H. Peragallo] on the West Coast of the USA is traced in three time periods: the early observations of 1920–1943, later publications in 1960–1990, and recent publications after known domoic acid events in 1991–1996. The genus has been widespread in these coastal waters, and more than a dozen species have been identified, with the number still increasing. Dominance shifts among species on time scales of weeks, months, and years. There is direct evidence of increases of cell numbers with even small amounts of upwelling, whereas some blooms have coincided with times of low expectation of upwelling. Original data from W.E. Allen’s notes provided by W.H. Thomas, Scripps Institution of Oceanography, suggest a possible explanation, borne out by recent culturing work. Viable cells can sink from the surface waters and rise in a different growth stage. Geographically, species in this genus have been st...