If toxic, planktonic organisms are present, they are filtered from the water along with other nontoxic foods. Whelks and moon snails can also accumulate dangerous levels of the toxin during red tide as they feed on contaminated shellfish. Lobsters, crabs, shrimp and finfish do not accumulate toxin and are safe to eat from affected waters. PSP is caused by saxitoxin, which is produced by G. tamarensis , and is one of the most potent toxins known to scientists. After ingestion, this poison immediately affects the nervous system, with symptoms usually occurring within 30 minutes.
Severity depends on the amount of toxin consumed.
Initial reactions are tingling of the lips and tongue, which spreads to the face, neck, fingertips and toes. Headache, dizziness and nausea follow. These symptoms may be mistaken for drunken conditions and are further aggravated by alcohol consumption. In severe cases, muscular paralysis and respiratory difficulty may occur with 5 to 12 hours. Fatalities from respiratory paralysis have been reported.