Alaska’s first shellfish toxin death in 10 years comes amid signs of spreading harmful algal blooms

Tests found toxin levels so in high at one site that eating a single mussel could be fatal.

By Yereth Rosen - July 21, 2020
Pacific blue mussels line rocks in Alaska which are alternately submerged and exposed by the changing tides. An Alaska resident recently died from PSP after eating blue mussels. (NOAA)

A resident of the Aleutian community of Unalaska/Dutch Harbor has died after eating toxin-laded shellfish from a local beach, Alaska officials reported.

It was the first death in Alaska from paralytic shellfish poisoning in 10 years, the Alaska Department of Health and Social Services said. The patient who died had eaten blue mussels and snails harvested on July 4, the department said last week.

The death comes at a time when harmful algal blooms are becoming more prevalent and moving north as waters off Alaska warm.

In recent days, monitors have shellfish on the Aleutian island with shockingly high levels of saxitoxin, the toxin produced by the harmful algae of the genus Alexandrium.

Samples have come back with levels of up to 11,200 micrograms per 100 grams, 140 times the 80 microgram-per-100 gram threshold for human safety, said Melissa Good, the Unalaska-based marine advisory agent for the University of Alaska Sea Grant program.

“That’s certainly a record for here. We’ve never seen anything like this,” Good said.

Shellfish from Chignik Lagoon, a community near the tip of the Alaska Peninsula and about 350 miles northwest of Unalaska, have also come back with toxin readings in the range of 11,000 micrograms per 100 gram, Good said.

“At that level, that makes one mussel potentially deadly,” she said.

[For the first time, scientists have found a dangerous toxin from algae in the Bering Strait and Chukchi Sea]

Levels were also high earlier in the month. The beach where the deadly mussels and snails were harvested had PSP toxins at about three times the level for safe consumption in early July, the Aleutian-Pribilof Islands Marine Advisory Program warned in a public notice. And butter clams found in June at King Cove Lagoon on the tip of the Alaska Peninsula had saxitoxin levels that were nearly 10 times the federal limit for safe consumption, the warning notice said.

For people who depend on wild shellfish for their diets and their cultural traditions, the increasing risk of potentially deadly algal toxin poison is “very, very scary,” Good said.

There is no reliable on-the-spot test for shellfish safety, she said, so harvesters who want answers have to send samples to an Alaska Department of Environmental Conservation laboratory in Anchorage.

That is a cumbersome process that, at best, takes a few days but might not even be possible if there are transportation difficulties, she said.

Another problem is the lack of medical infrastructure on the island and other remote sites where people depend on wild shellfish, Good said. The victim who succumbed to the algal toxin died after being flown to an Anchorage hospital.

PSP toxins, commonly called saxitoxins, block the movement of sodium through the nerve-cell membranes and thus interrupt nerve impulses.

“Without the movement of sodium, nerve cells cannot function, causing the PSP symptoms of tingling, numbness, disorientation, paralysis, nausea, respiratory failure, and even death,” an Alaska Sea Grant program overview says. “PSP toxins are estimated to be 1,000 times more toxic than cyanide, and as little as 1 milligram of saxitoxin is enough to kill an adult human. Eating a single shellfish, such as a clam, that is contaminated with PSP toxin has the potential to cause death.”

The toxins cannot be removed through cooking or freezing, and there is no medical antidote, officials warn.

Prior to the Unalaska death, there were four other paralytic shellfish poisoning deaths in Alaska between 1994 and 2010 and there were 117 cases reported between 1993 and 2014, according to the department’s epidemiology section.

Problems with algal toxins are not new in Alaska or the Pacific Northwest. Blooms have occasionally shut down shellfish harvests, and the toxins have been memorialized in Alaska history. A site in southeast Alaska was named Poison Cove after toxin-laden mussels harvested there killed about 150 people in 1799.

But as Alaska waters have warmed, blooms of toxin-producing algae have become more frequent and have spread north, making them a threat to Arctic marine environments.

Last year, scientists documented dense toxin-producing algal blooms in the Chukchi Sea north of Utqiagvik, the northernmost U.S. community. The scientists also discovered, for the first time on record, dangerous levels of toxins in clams from the Bering Strait region and the Chukchi Sea. The clams, extracted by researchers from the seafloor off the coast, had levels of saxitoxin above the limit for safe consumption by people.

Traces of algal toxins have been discovered in marine mammals in all waters off Alaska, including the Arctic Ocean. In one case, a walrus found on the Bering Strait island of Little Diomede had levels of saxitoxin in its intestinal contents that were above the limit for human consumption.

Algal toxins are being considered as a possible contributor to successive die-offs of birds and marine mammals that have been recorded over the past several years.

Those die-offs appear to be continuing.

At Unalaska, Good said, a fisherman found about 30 dead puffins in an area thick with sand lance, a type of fish well-known for accumulating algal toxins. Good said she has sent one of the dead birds to the U.S. Geological Survey’s National Wildlife Health Center laboratory in Wisconsin.

There have also been local discoveries of dead sea otters and one dead sea lion, she said. Causes of their demise remain unknown.

In the Bering Strait region, about 30 dead horned puffins and murres were found along a stretch of beach in the Nome region, and other dead seabirds were found near Savoonga, one of the villages on St. Lawrence Island, said Kathy Kuletz of the U.S. Fish and Wildlife Service.

Birds sampled to date have been emaciated, with no signs of avian disease, Kuletz said by email. Tissue samples will be tested for harmful algal toxins, she said.

“As of this date, it is a series of relatively small die offs (near as we can tell), but certainly of concern and folks are keeping an eye out, locally, for more,” she said by email.

Monitoring this year has been difficult because research cruises were canceled, as were the normal annual surveys of bird colonies in the far-flung Alaska Maritime National Wildlife Refuge, she said.