How will the Bering Strait respond to harmful algal blooms?

By Megan Gannon
Emma Pate did not grow up hearing about harmful algae in the Bering Strait region. But now she spends about 75 to 100 percent of her time at work thinking about these tiny, toxin-producing organisms that have become a new threat, with uncertain impacts, in Arctic waters.
Pate is the training coordinator and environmental planner in the Office of Environmental Health at Norton Sound Health Corporation. Working with tribes across the region and Alaska Sea Grant, she is trying to establish a sustainable new monitoring program to keep track of harmful algae that may be multiplying rapidly in the seawater where communities conduct subsistence activities.
Researchers have long been worried that harmful algal blooms will become a more common feature of a warming Arctic. Last summer, a massive bloom was detected off the coast of Western Alaska, almost by chance, when scientists sailing through the Bering Strait and Chukchi Sea found worryingly high levels of Alexandrium catenella. This single-celled organism can produce saxitoxins, which can contaminate shellfish and lead to paralytic shellfish poisoning, or PSP, in humans.
“What happened this last summer brought a lot of attention to the reality that there are significant cell counts out there in our water,” Pate said.
The researchers aboard the ship coordinated with Pate and Alaska Sea Grant to issue unprecedented local advisories about the subsistence use of clams, mussels and other shellfish. These animals can become dangerous, or even deadly, for humans to eat when they take up too much Alexandrium.
“We had people not eating what they normally would, which created hardship, because it’s normal for them to gather their seafood and not go to the store,” Pate said. “All of a sudden, for those that chose to err on the side of caution and not consume those foods that may be affected, they ended up spending more at the grocery store.”
The event added momentum to a monitoring project Pate had already been working on over the last few years. Pate has now recruited and started training tribal environmental coordinators in Savoonga, Elim, Unalakleet, Brevig Mission and Shaktoolik to take weekly seawater samples looking for harmful algae. So far, only Savoonga, Elim and Unalakleet have their own microscopes so that coordinators can analyze samples in the village. The other villages will have to send their samples to Nome. Pate and her collaborators will be looking for the presence and absence of three target species— Alexandrium as well as Pseudo-nitzschia and Dinophysis, which can also be toxic to humans in high concentrations.
If the coordinators find elevated counts of a harmful algae, they will report that data to the National Oceanic Atmospheric Administration, or NOAA, and work on getting residents to collect food samples to send them away for testing at a lab. “It’s always a challenge to ask people to give up their traditional foods they gathered, and it puts them in the position of giving up something they normally consume as part of their diet,” Pate said.
Bigger problem
The local monitoring effort is one step in establishing a better system to track and respond to dangerous algae blooms in the region as researchers try to gain a better understanding of how these microscopic species affect the larger animals up the food chain, such as walruses and seabirds.
“Now this region has to really figure out how to deal with what’s going to be a recurring threat,” Don Anderson, a senior scientist at the Woods Hole Oceanographic Institution, or WHOI, told the Nugget last week at the annual Alaska Marine Science Symposium in Anchorage.
Anderson and Pate were among a few dozen experts and coordinators gathered in a workshop, both virtually and in person, to discuss harmful algal blooms at the symposium. A big topic of discussion was this summer’s bloom that scientists from Anderson’s lab had observed while aboard the Norseman II research vessel.
The researchers had been taking samples from the Bering Strait and Chukchi Sea, hoping to learn more about Alexandrium. Typically, concentrations above 1,000 Alexandrium cells per liter of water are considered dangerous. During their 28-day cruise in 2022, the researchers were finding 100,000 cells per liter in some locations. The team had been analyzing samples from the region for several years in a row, but they had never seen such high numbers.
What also made last summer’s cruise unique was its focus on algae. In the past, researchers from Anderson’s lab had tagged along on other research cruises, squeezing into spare bunks and taking samples opportunistically. But Anderson and another WHOI scientist, Bob Pickart, got funding from the National Science Foundation to undertake a research cruise specifically dedicated to studying harmful algae.
“That was really great, because it gave us the opportunity to actually decide where the boat was traveling based on where the harmful algae were,” said Evie Fachon, a PhD student in Anderson’s lab who was on the boat.
Without another algae-dedicated cruise, the researchers will again have to rely on ships of opportunity to collect samples, but that might mean a longer lag time for analysis and spreading awareness about high harmful algae counts.
“We will probably have a very difficult time giving any real-time information,” Anderson said.
As for her own monitoring program, Pate is wary of creating a system that is dependent on getting grants.
“I’ve been told by a number of individuals I spoke with since we started engaging in this program that there’s a lot of funding to initially set it up, but to maintain it is a challenge,” she said. “That’s why we’re working with the tribes and agents that want to participate to establish a solid foundation for this to be long term, keeping in mind that they have existing obligations or other environmental duties.”

Sleeping giant
Throughout the symposium, researchers had presented findings that highlighted how harmful algal blooms are likely to become a more common occurrence as Arctic Alaska warms faster than just about anywhere else on the planet.
For decades, even centuries, harmful algae have been building up on the bottom of the ocean off Arctic Alaska. Alexandrium cells clumps together, forming cysts that sink to the seafloor and can lay dormant for many years. According to recent scientific observations, the massive accumulation of Alexandrium cysts in the Chukchi Sea is the second largest in the world. The only area that has higher concentrations is in the nearby Gulf of Anadyr. The cold water has limited how much these colonies of microorganisms can grow, but now under warming conditions, Anderson has likened these cyst beds to a “sleeping giant” that will fuel future blooms.
Looking ahead to that reality, Nome-based Alaska Sea Grant Agent Gay Sheffield, who has been coordinating with Pate, told the workshop in Anchorage that she wanted to know what resources would be available for communities in the Bering Strait region and further north to respond.
“We have people all up and down that coast that are relying on maritime subsistence for their everyday foods,” Sheffield said.
Raphaela Stimmelmayr, a biologist with the North Slope Borough’s Department of Wildlife Management, echoed her remarks. She commended the researchers in the room for taking an interest in harmful algal blooms and said government entities like NOAA and state agencies now need to ensure that appropriate response mechanisms are in place.
“We do know that a potential endpoint of this is the death of somebody,” Stimmelmayr said. “I think we need to actually start talking about it, not because I’m trying to instill fear, I’m just saying that the system is so unpredictable now, and we just don’t know enough.”
Others warned that major challenges remain for assessing the risk to coastal harvesters, even in regions with more experience monitoring such blooms.
Julie Matweyou, a Kodiak-based Alaska Sea Grant agent, has been studying harmful algal blooms in her region for the last two decades and trying to ensure that residents are not eating shellfish loaded with neurotoxins. Alaska has among the highest number of PSP cases in the U.S., and the state’s Section of Epidemiology released a bulletin last year showing that Kodiak accounted for about a quarter of the state’s cases between 1993 and 2021. Although the threat of PSP and other conditions has been present for decades in the Gulf of Alaska, Matweyou said the problem of how to best monitor and respond has not been entirely resolved there either.
“Effectively, the state has been saying, ‘Don’t eat the shellfish’ for many, many, many years, and that message doesn’t work in our communities, nor do I want it to work in our communities,” Matweyou said. “People need to eat this food.”
She said that levels of toxins in shellfish can vary widely, even between different locations on the same beach, highlighting the need for monitoring, testing and decision-making at the community level, or even the harvest site level.

Food web
Another challenge is understanding how toxic algae affects animals beyond shellfish.
“The reason that shellfish have been studied so thoroughly is because that is really the main exposure risk for [harmful algal bloom] toxins to humans worldwide,” said Kathi Lefebvre, a NOAA research biologist. “We know that shellfish can accumulate high levels of toxins during blooms, and so there have been illnesses related to eating those. There’s been a lot of work done to set regulatory limits seafood safety globally.”
But less is known about harmful algae’s effects on other vectors. Lefebvre is the lead investigator on a five-year collaborative project called ECOHAB, which seeks to track saxitoxin in the broader Arctic food web—from clams and krill to worms and fish. She also started the Wildlife Algal-Toxins Research and Response Network over a decade ago to measure algal toxin presence in stranded and subsistence harvested marine mammals.
While this past summer’s bloom was startling, Lefebvre said 2019 was a bigger turning point for her work. It was the warmest year on record in the Bering Sea, and her team collected deep-water clams in the region, all the way to Utqiagvik, that had toxin levels above seafood safety regulatory limits.
“We were surprised by that,” she said. “We knew the toxins would be there. But I did not know that they would be high. And then the toxins just moved through the food web. One hundred percent of the walruses contained toxin levels. Two of them had pretty high levels close to regulatory limits. So for me, 2019 was really the eye-opening year of what can happen.”
For now, Lefebvre said she feels confident that muscle and blubber of walruses are not likely to have levels of toxins that are dangerous to humans, but she wants more data on other tissues. “These toxins are released from the body through things like urine, so the question is, could kidneys have high levels? We don’t know for sure, and we want to check that,” she said.
But even if the consumption of walrus meat is not a direct risk to humans, declining walrus health due to harmful algal blooms in warm years still impacts subsistence communities in Alaska, who also harvest clams directly out of the guts of the walruses.
“That is a food security issue,” Lefebvre said.


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