AN OUTBREAK OF DOMOIC ACID POISONING ATTRIBUTED TO THE PENNATE DIATOM PSEUDONITZSCHIA AUSTRALIS1

ABSTRACT A bloom of the pennate diatom Pseudonitzschia australis Frenguelli (= Nitzschia pseudoseriata Hasle) occurring in Monterey Bay, California, in early September 1991 coincided with an episode of mortality in brown pelicans (Pelicanus occidentalis) and Brandt's cormorants (Phalacrocorax penicillatus). High levels of domoic acid (DA), the amnesic shellfish poisoning toxin, were recorded in the plankton samples. Furthermore, high levels of DA, as well as numerous remnants of P. australis frustules, were found in the stomach contents of affected birds and in the visceral contents of local anchovies, a principal food source of seabirds. This is the first confirmed report of DA poisoning since the original 1987 episode in Atlantic Canada caused by Nitzschia pungens Grunow forma multiseries Hasle. It suggests another species of planktonic pennate diatom is capable of producing DA and that herbivorous finfish can act as vectors for this toxin.