Local Biotoxins and Toxic BacteriaWritten September 30, 2013, published in October 2013, all photos by Kathleen Sayce
Bottom line: Biotoxins have been here for a long time.
|Prorocentrum species are associated with biotoxins in some areas. This genus is common in local waters. On the south coast of Washington, it has not been associated with water-borne toxins.|
PSP:At the top of the list of locally common toxins is Paralytic Shellfish Poisoning (PSP), caused by saxitoxin, which is produced by species in the dinoflagellate genus Alexandrium, other dinoflagellates, cyanobacteria, and at least one species of pufferfish. Shellfish may store these toxins to reduce predation; it remains in animal tissues for weeks to years. Poisoning occurs by eating the shellfish. Saxitoxin is water soluble, and is heat and acid-stable, which means that cooking makes no difference to its toxicity. Alexandrium species are seen regularly along the Pacific Northwest coast, and are common in local waters during warm weather, spring through fall. Otters, seals and whales have died from high doses of PSP.
|Pseudo-nitzschia species produce domoic acid, and locally were responsible for many closures in the 1990s in local waters.|
ASP:Amnesiac Shellfish Poisoning (ASP) is caused by domoic acid, a small protein produced by diatoms in two genera, Pseudo-nitzschia and Nitzschia. Domoic acid concentrates in fat cells as it moves up the food chain from diatoms to zooplankton, shellfish, crabs and small fish to larger fish; this is called bioconcentrating. Birds, marine mammals and humans are neurologically affected by ASP. Domoic acid is unaffected by heat or other food preparation methods, and can persist in animal tissues for years following large blooms. This biotoxin may be a relatively recent arrival, reaching the West Coast after WWII in ballast water on commercial ships. In some years it has been a dominant species outside the surf zone in local waters.
DSP:Diarrhetic Shellfish Poisoning (DSP) is generally not life threatening, though profoundly uncomfortable to victims. Caused by okadaic acid, and found in two genera of dinoflagellates, Prorcentrum and Dinophysis, the result is diarrhea, which begins within an hour of consumption and lasts about one day. No fatalities have been recorded from known cases of DSP. These dinoflagellates are common in local waters each summer, but are rarely dominant in blooms.
|Dinophysis species are common summer phytoplankton in local waters. This dinoflagellate genus causes DSP in warmer waters, such as in Florida.|