Autecology of the diatom Pseudonitzschia australis, a domoic acid producer, from Monterey Bay, California

Pseudonitzschia australis Frenguelli has been identified as the domoic acid producer responsible for pelican mortalities and shellfish and other seafood quarantines on the west coast of the United States. During autumn 1991, Monterey Bay was the focus of the highest reported concentration of domoic acid in shellfish and anchovies. P. australis has been identified as an important and persistent component of the phytoplankton assemblage in Monterey Bay and contiguous waters for the past 3 yr. High abundances occurred consistently in the autumns of 1988 to 1991, as well as in March 1990 and July 1991. Maximum abundance, recorded in November 1991, was in excess of 6 × 105 cells l−1. Per cell domoic acid concentrations in October and November 1991 ranged from 3 to 31 pg and water column burdens ranged from 0.1 to 6.7 μg l−1. In their tissues, anchovies contained quantities of domoic acid equivalent to 2 d worth of ration, implying high incorporation and/or low depuration rates.