Searching for a cause of ASP, researchers discovered domoic acid, a neurotoxic amino acid, in water samples retrieved from the area. The source of the domoic acid was unknown. After the outbreak in Canada, a domoic acid-related poisoning occurred in Monterey Bay, California, killing pelicans and cormorants. An examination of several papers related to Pseudonitzschia australis , the diatom implicated in the California incident, is compared to the scientific data and results gathered by researchers of the Canadian occurrence. Before continuing, it is necessary to provide some information about phytoplankton.
Phytoplankton are microscopic, photosynthetic, free-floating organisms in the ocean.
N. pungens and P. australis are diatoms, a type of phytoplankton that has a cell wall composed of silica, called a frustule. The frustule has two parts that fit together like a petri dish. In N. pungens , a pennate diatom, the cell wall is stretched out giving the organism the appearance of a symmetrical flattened banana. P. australis is also a pennate diatom and has a shape similar to N. pungens . Many different kinds of phytoplankton exist, and only a few of them are toxic.