Harmful algae bloom detected in Bering Strait waters
Residents of the Bering Strait region are urged to use caution and stay informed when harvesting certain seafoods this summer. High concentrations of harmful algae called Alexandrium catenella have been detected by a research vessel in the region’s waters near St. Lawrence Island, Wales and Little Diomede over the last week.
“We don’t have all the answers, but what we do know is it can potentially be a danger to human health,” said Emma Pate, an environmental planner at Norton Sound Health Corporation.The single-celled algae species Alexandrium is known to produce a suite of toxins called saxitoxins that can cause paralytic shellfish poisoning in humans. Those toxins can’t be removed from seafood through cleaning, cooking or freezing. “A concentration of 1,000 cells of Alexandrium catenella per liter of seawater is considered dangerous and high enough to trigger a public advisory for nearby coastal communities to be cautious when consuming marine wildlife resources, such as: clams, crabs, tunicates, etc. as well as the organs of marine mammals and seabirds,” said a public service announcement issued by NSHC and other partners monitoring harmful algae in the region.
A map of the Alexandrium detections showed several spots with concentrations much higher than 1,000 cells per liter of seawater. A sample collected on July 29 about 75 nautical miles north-northeast of Savoonga had 47,000 cells per liter. Another sample taken on July 28 about 13 nautical miles southwest of Wales had 6,000 cells per liter. The same day, about 4 nautical miles east of Diomede, a sample had 7,000 cells of Alexandrium per liter of seawater.
Further lab analyses will confirm the algae species identity and toxicity. A high concentration of cells does not necessarily translate to high toxicity, and conversely, the algae can be highly toxic without being highly concentrated. That variability makes it hard to know the exact risks, said Louisa Castrodale, an epidemiologist at the Alaska Division of Public Health.“There’s not a color indicator or something like that where you could look at a clam and see that it is definitely containing toxin or not,” said Castrodale. “Making sure that people have awareness of what symptoms could look like is really important, as is making sure that people know, if they do start experiencing symptoms, to get medical attention.”
The classic symptoms associated with paralytic shellfish poisoning are tingling around the mouth and a weird feeling of floating.
“If there’s a really significant load of toxins, it will impact somebody’s breathing,” Castrodale said. “We don’t want people to get to that point because then it really is a medical emergency.”
Alaska Sea Grant Agent Gay Sheffield said the best thing members of the public can do is to be informed and to contact healthcare providers if they feel sick after eating certain marine foods.
“The fact that the Norton Sound Health Corporation is right in the middle of this is awesome,” Sheffield said. “The clinics have already been informed about this event. The safety net is there. It’s not perfect. But the other thing this shows this whole situation shows to me is rural Alaska is taking care of this situation as best we can. We’re self-rescue. We are self-sufficient. We look after each other. We have many, many things we have to zig and zag for nowadays, and this is just another one.”
Harvesters in other parts of Alaska have gotten familiar with the risks of harmful algae. But for Arctic waters, these blooms are an emerging threat—one that’s expected to become more frequent as the climate warms.
Between 1993 and 2021, the state has seen at least 132 cases of paralytic shellfish poisoning—five of them fatal. The most recent death in Alaska caused by paralytic shellfish poisoning occurred in July 2020 after a person consumed blue mussels and snails collected from Unalaska.
Sheffield and Pate noted that subsistence users are making assessments all the time about the health of their harvests and drawing on longstanding traditions to help them make decisions.
“You don’t get a manual on how you butcher a seal, so you really have to follow what was learned over time on how to safely process and prepare subsistence foods,” Pate said.
Now knowledge about algal blooms will become an important facet of subsistence harvesting.
“I’ve lived here all my life, I grew up doing all kinds of subsistence activities, and I still eat all the traditional foods that come from the ocean,” Pate said. “One of the questions I’m always asked is, do I still eat these foods? Yes, I do. But I have more of an awareness about it.”
The samples that revealed a bloom were collected by an instrument aboard the Sikuliaq, a research vessel owned by the National Science Foundation and operated by the University of Alaska Fairbanks. The ship was on a cruise led by scientists studying plankton at the ice edge in the Chukchi Sea. They were sailing back to Nome when water samples started turning up high concentrations of Alexandrium. Those samples were being monitored remotely by researchers at the Woods Hole Oceanographic Institute in Massachusetts who detected last year’s unprecedented bloom while on an Alexandrium-focused cruise aboard the Norseman II.
The Sikuliaq is now in the Port of Nome for dockside operations ahead of its next cruise. That means it won’t produce any samples from July 30 through August 6. And when the vessel leaves again, it will continue to take opportunistic water samples, but it won’t be chasing the algal bloom. The next team of researchers to board the ship will be collecting cores on the seafloor. They’ll be heading to the southern Bering Sea.
Pate and Sheffield are trying to patch together additional sampling. They are taking their own coastal seawater samples near Nome. Pate is coordinating with tribes in the region to test seawater samples from other villages. An NSEDC tender vessel will also begin collecting water samples while it travels in the region’s waters. Sheffield and Pate are also happy to accept subsistence-harvested foods to be sent away for toxicity testing.
“A lot of people are not going to give that up because they’re very delicious, traditional foods, and it takes a lot of work to gather those,” Pate said. “When you ask them to give that up, you’re asking them to give up a meal.”
And there’s a time lag to get those toxicity results. But testing could help prevent harvesters from eating foods that make them sick. A butter clam harvested north of Savoonga and sent in for testing during last year’s bloom was found to be five times over the seafood safety limit.
Individuals who feel sick after eating any seafoods are urged to contact their healthcare provider immediately. Those concerned about their subsistence-harvested seafoods can contact either Gay Sheffield at (907) 434-1149 or Emma Pate at (907) 434-0227 to coordinate shipping and lab testing for any saxitoxin levels in those foods.