For the first time since last winter, paralytic shellfish poisoning (PSP) risk factors for butter clams sampled on beaches near Pats Creek have dropped back to normal.
Wrangell Cooperative Association’s Indian Environmental General Assistance Program office made the announcement last week, after samples taken July 24 showed decreased levels of saxitoxin. The cause behind PSP, elevated saxitoxin traces were first discovered at the site in January.
Saxitoxin is a deadly neurotoxin produced by phytoplankton of the genus Alexandrium. When appearing in large blooms in nearby waters, the plankton can emit saxitoxin in enough quantity to be absorbed by filter feeders like clams and oysters. While the toxin does not impact the bivalves themselves, it can be transmitted to humans through ingestion. Saxitoxin poisoning, better known as PSP, usually becomes apparent with a numbness of the oral membranes, with more severe cases entailing nausea, vomiting, paralysis, respiratory failure and ultimately death.
Wrangell’s IGAP has since 2016 been examining area shellfish in connection with Sitka Tribe of Alaska, which has spearheaded a regional testing program through the Southeast Alaska Tribal Toxins project. Its laboratory in Sitka is equipped to identify different marine biotoxins, of which saxitoxin is just one, the first in the region. The program works in concert with other tribal partners, state and federal agencies, and regional fishing groups to provide a wider map of potential threats to subsistence users.
In Wrangell, test samples are taken on a weekly basis, with specimens of quick-filtering shellfish like blue mussels providing a recent snapshot of toxin levels along local beaches. Butter clams take considerably longer to process out the saxitoxin they have absorbed, posing an extended risk for a year or more.
Soon after initiating its program, in August 2016 Wrangell IGAP learned butter clams near the Shoemaker Bay helipad had unsafe levels of saxitoxin present in them. While those levels have fluctuated since, samples have consistently shown a risk to human health in subsequent tests, and residents are still cautioned not to eat butter clams from that beach area.
A similar risk was detected at Pats Creek in January, but these most recent samples indicate those butter clams’ level of toxicity has dropped below the risk threshold set by the state.
As well as the toxins produced by Alexandrium, Wrangell’s IGAP also remains on the lookout for phytoplanktons Dinophysis and Pseudo-nitzschia, which produce other toxins harmful to humans.
Dinophysis can produce okadaic acid, which can cause a non-fatal diarrhetic shellfish poisoning. Pseudo-nitzschia produces domoic acid, which can lead to fatal amnesic shellfish poisoning. Symptoms include vomiting, nausea, diarrhea, cramps and hemorrhagic gastritis, as well as other neurological problems.
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