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Biotoxin Program The Biotoxin Program performs year-round monitoring of Paralytic Shellfish Poison (PSP, also known as "red tide"), and Amnesic Shellfish Poison (ASP, or domoic acid) in molluscan shellfish. Biotoxins are poisons caused by microscopic toxin-producing algae (a type of phytoplankton) that naturally occur in marine waters, normally in amounts too small to be harmful. However, a combination of warm temperatures, sunlight, and nutrient-rich waters can cause rapid plankton reproduction, or "blooms". Molluscan shellfish (those that have a hinged shell, such as clams, mussels, oysters, geoduck, etc.) are filter feeders and ingest the algae into their systems, where toxins concentrate. It is important to note that cooking does not remove these toxins from shellfish. Cooking will kill the organisms, but the toxin remains. The term "red tide" is a misnomer...paralytic shellfish poison and domoic acid poison are rarely associated with a red tinge to the water. Both PSP and domoic acid can be present in large amounts when the water appears clear. Reddish coloration of the water is more commonly associated with non-toxic organisms. Paralytic shellfish poison is caused by the dinoflagellate Alexandrium catenella; domoic acid poison is caused by the diatom Pseudo-nitzschia pungens. Shellfish in both recreational and commercial harvest areas are regularly tested for biotoxins. When toxin is detected at dangerous levels, harvest areas are closed and do not reopen until levels drop again. Mussels accumulate toxins more quickly than other types of shellfish, and are a good indicator species. Butter clams store toxins for longer than any other species, and can remain toxic for more than a year after toxin levels in the surrounding waters subside. Biotoxin testing must be done in a lab. All Washington shellfish testing is currently performed at DOH's Public Health Laboratories in Seattle. At this time there is no certified reliable biotoxin test that can be performed outside of a laboratory environment. A marine Biotoxin Bulletin lists beaches that are closed to recreational harvest due to significant levels of biotoxins. This bulletin is updated as changes occur. For more information on PSP, read the PSP Fact Sheet. In the summer months, the Biotoxin Program also monitors levels of a bacterium called Vibrio parahaemolyticus, and closes harvest areas when bacteria levels are high. V. parahaemolyticus can cause an intestinal illness called vibriosis. Unlike PSP or ASP, vibriosis and the accompanying flu-like symptoms can be avoided by thoroughly cooking shellfish. This is especially important during summer months, when the bacteria is more common. For more information, see our list of Biotoxin Publications
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The Harmful Algae Page (Woods Hole Oceanographic Institution) Olympic Region Harmful Algal Blooms Project (Northwest Fisheries Science Center)
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