Science

High levels of toxins in clams follow rapid warmup in Gulf of Alaska waters

Warm conditions in the waters surrounding the Alaska Peninsula have produced algal blooms that threaten the safety of food important to coastal residents, according to the first official report this year of dangerous toxin levels in shellfish.

The first tests of clams gathered from Chignik Lagoon produced levels of saxitoxin — the toxin that causes paralytic shellfish poisoning — at a level nearly eight times the limit for safe consumption, according to testing arranged by the Knik Tribal Council.

That reading was for a sample of razor clams, according to a tribal council notice sent out last week. Razor clams are commonly harvested from Alaska beaches for personal use.

Also gathered there and likely to have high levels of saxitoxin were butter clams, a species known for holding the toxins for extended time periods — and also an important food source for personal-use harvesters.

The high toxin reading coincided with a quick warmup of Gulf of Alaska waters, said Bruce Wright, senior scientist with the Knik Tribal Council.

[Alaska has among the nation’s highest rates of paralytic shellfish poisoning, but reported incidents are declining]

Alexandrium, the algae that produces the toxin that causes paralytic shellfish poisoning, needs some warmth to bloom, Wright said. “Alexandrium blooms can take off when you have sea surface temperatures that are about 8 degrees Celsius,” or 46.4 degrees Fahrenheit, he said.

And now, after a year of relatively cool conditions in the Gulf of Alaska, temperatures in the areas of the Gulf have shot up well above that, according to National Oceanic and Atmospheric Administration measurements. Water temperatures off Anchorage were measured at over 58 degrees, for example, according to NOAA.

Wright has studied and monitored algal toxins for several years. He is a former University of Alaska professor, NOAA scientist and senior scientist for the Aleutian Pribilof Islands Association. Now in his scientific role with the Knik Tribal Council, he coordinates the testing of shellfish on beaches stretching from Southeast Alaska to the Aleutians.

“I always want people to not eat the subsistence clams or mussels unless they’re sent in a sample for testing,” Wright said.

That is not always easy for people to do, he said. It requires collection of samples, packaging and mailing them from sometimes remote locations to Anchorage, where Wright picks up the samples, does the initial processing of them and delivers them to the Department of Environmental Conservation laboratory in the city. A test at the DEC lab costs $125, which can present another impediment, Wright said.

Along with monitoring shellfish safety, Wright is focusing this year on a related subject: the levels of algal toxins being encountered by salmon, a subject just starting to be researched.

Of particular concern are king salmon and silver salmon, which feed on sand lance, a type of fish known to absorb algal toxins. “Sand lance is a forage fish that moves the toxins through the food web,” he said. While there are likely many contributors to recent salmon crashes in the Yukon River and elsewhere, chronic exposure to algal toxins may be a factor, he said.

This summer, he plans to conduct a program to track salmon exposure to algal toxins by testing fish livers. “This year, we’ll be getting close to 1,000 king salmon livers from the Yukon River,” he said. The program is being conducted in cooperation with the U.S. Fish and Wildlife Service and the Alaska Department of Fish and Game, he said.

There are signs that algal toxin dangers are expanding north in Alaska waters as the climate warms. A landmark 2016 study found traces of toxins in the bodies of marine mammals as far north as the Beaufort Sea.

Wright said he worries about that trend.

“What will happen when the northern Bering Sea and the Chukchi Sea and the Beaufort Sea start warming up? That’s going to be scary,” he said.

Originally published by the Alaska Beacon, an independent, nonpartisan news organization that covers Alaska state government.

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