Latest samples of butter clams from Shoemaker Bay beaches show levels of saxitoxin have halved since this summer, when specimens were found to be a health hazard. The clams are still considered a health risk, albeit at a lower level.
Wrangell Cooperative Association’s Indian Environmental General Assistance Program (IGAP) staff have been collecting samples of mussels and other bivalves from the beach on a weekly basis, which then get tested at a Sitka lab for several different toxins. In August the program reported elevated levels of saxitoxin, which causes paralytic shellfish poisoning (PSP), which can be fatal.
Saxitoxin is produced by Alexandrium, a variety of phytoplankton which can bloom in large enough numbers to taint nearby waters. Filter-feeders like clams and oysters end up ingesting and absorbing the toxins from the water, which can take months or even years to pass them.
IGAP technician Kim Wickman explained butter clams are affected a particularly long time, taking upward of two years sometimes to filter harmful toxins. Harmful to humans, that is. The clams themselves remain pleasantly unaffected by saxitoxin.
“We’re not sure when they obtained these,” she said of the clams’ toxins.
In humans, saxitoxin causes paralysis by blocking sodium channels in neurons, preventing them from functioning normally. PSP begins with a numbness of the oral membranes, and severe cases can include nausea, vomiting, neurological effects, respiratory failure and death.
The state sets a safety threshold of 80 micrograms for saxitoxin, while this summer samples at Shoemaker had shown a level of 212. Last week’s sample came back at 104, an improvement but still worth taking under advisement.
Wrangell IGAP’s alert was posted to the Sitka-based Southeast Alaska Tribal Ocean Research website at http://www.seator.org/data. The site collects updated data from 28 different sites in 16 communities around Southeast, focused on saxitoxin, domoic acid and other harmful toxins to be found in shellfish. Findings at the program’s laboratory are not certified, only precautionary.
The SEATOR program and its laboratory were established by Sitka Tribe of Alaska in order to give local shellfish harvesters a way to test clams and other shellfish important to subsistence. Previously the only lab in the state capable of such testing was in Anchorage, and catered primarily to commercial fisheries.
In 2013, the Southeast Alaska Tribal Toxins network was started to coordinate and share information between the region’s tribal governments. Wrangell’s IGAP began collaborating with SEATT in April, beginning with its monitoring at Shoemaker Bay. Wickman explained a second site near Pats Landing is also being established, as it is another popular place to collect shellfish. She is collecting baseline data at the moment, but the site should be ready for regular testing early next year.
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