Pseudo-nitzschia is another common diatom in Washington waters. The cells
are long and slender and are joined into so-called stepped colonies by the
overlapping of the cell ends. Some kinds of Pseudo-nitzschia produce a toxic
compound called domoic acid. Shellfish (crabs, clams, mussels) that feed on
phytoplankton containing high numbers of Pseudo-nitzschia can accumulate
domoic acid and become dangerous for other marine life and humans to eat.
Amnesic Shellfish Poisoning is the name given to the illness people get after
eating shellfish containing domoic acid.