Temperatures in Arctic waters are warming and sea ice is diminishing. With that could come the potential for harmful algal blooms that produce toxins that can affect marine life. Pacific Northwest scientists are now turning to Arctic bowhead whales to get a better idea of the potential ramifications of toxin exposure caused by the algae.
"The reason we want to use the bowheads is because they're harvested. They're being used and it's the closest thing you can get to a planned study. We obviously don't want to hunt any animals just for this, so we are using animals that are already used for other reasons and it gives us a large number of animals to work with," said Kathi Lefebvre, a fisheries research scientist with the National Oceanic and Atmospheric Administration (NOAA) and founder of the Wildlife Algal Toxins Research and Response Network for the West Coast, or WARRN-West.
A recent study led by Lefebvre looked into the risks posed to Arctic mammals by biotoxins like domoic acid, produced by Pseudo-nitzschia algae, and saxitoxin, produced by dinoflagellates and associated with paralytic shellfish poisoning.
With the initial study, which included whales, walrus, sea lions and other animals, researchers had to rely on samples collected around the state when they were available -- when there was a stranding or a subsistence harvest, for example.
That meant there was no regular sampling. There were no set intervals between samples, no guaranteed sample size or number of animals from any particular area, and no reliable tracking of where those animals had fed or traveled.
That made it hard to establish a dependable time series that could be analyzed for trends and irregularities.
"Now, we're going to have a consistent set of a large number of whales that are harvested either in spring or fall and we know exactly where they're feeding," she explained. "So, we can do a time series and see if anything correlates with environmental factors. We also should be able to see if there appears to be an increasing trend of toxins over time."
In addition, bowheads will provide an interesting perspective on the ecosystem of the Arctic as a whole. The whales function as a sentinel species, meaning scientists can learn about what's happening throughout the food web by analyzing the whales, which sit at the top.
Working with the North Slope Borough and the whaling community, she and her team will analyze about 160 bowhead whale samples they have from 2004 to the present. That adds up to about eight to 19 animals per year over a 15- to 17-year timespan. Then, they'll look back at the environmental data from those harvest periods.
"We're going to see if we can find any climate factors like warmer waters, less sea ice, more sunlight, currents, other oceanographic features, food web features, see if there's anything that correlates with toxin levels that might be able to tell us if there's going to be a trend of increasing toxins over time or if there's something that predicts if there's toxins at a given time," she said.
Since the initial study's release, the predominant concern from locals along the Arctic coast has been about risks to the people who rely on marine animals for food.
"The thing is, we have a lot of coastal communities and community members who rely on the acquisition of non-commercial maritime resources, so not just marine mammals, but the fish, seabirds and shellfish," said Gay Sheffield, a project researcher based in Nome. "One of the concerns that has been raised by people since the study came out is, how will we know when the food is affected?"
For marine mammals, the risk to humans from the meat and fat of a whale exposed to the toxin is very low, Lefebvre said.
"Eating the tissues like the blubber and the muscle, it's very, very unlikely that toxin levels would ever be near the regulatory limit in those tissues because these are water-soluble toxins, so they don't accumulate in the tissues and blubber of mammals. They're passed quickly through the feces and urine," she said.
For Lefebvre, the main concern she has identified is the potential effect on the marine mammals themselves from long-term low-level exposure to the toxins.
"It's more a concern about the effect on the marine mammals themselves and the loss of that resource, so more of a food-security issue," she said.
The concern stems from the results of the initial study in which it was found that algal toxins, either domoic acid or saxitoxin, or both, were present in all 13 species of sampled animals that came from locations around coastal Alaska, from Southeast to Barrow. It was already known that the toxins were present in some areas, but the extent of their proliferation came as a bit of a shock to Lefebvre.
Lefebvre's surprise at the findings carries weight as she has a long history with domoic acid on the Pacific coast.
As a first-year graduate student at the University of California, Santa Cruz in 1998, she focused her research on domoic acid poisoning in humans, of which the first case was reported in Canada in the 1980s. She was interested in learning how it moved through the food web.
That year, hundreds of sea lions stranded themselves on the central California coast. They were having seizures and demonstrating signs of potential poisoning, at the time thought to be caused by high mercury levels.
Lefebvre collected samples from the sea lions, including feces and urine, and anchovies the animals would eat in the surrounding waters, and tested them. She found evidence of domoic acid in her samples.
"Every year since 1998, marine mammals have suffered from domoic acid poisoning in central California," Lefebvre said. "Now, I'm in Seattle, and we had never seen a seizing sea lion north of California for the last 17 years until this year. So from my perspective, I'm thinking, holy cow, it's been happening every year since and now we're getting it here. Then, at the same time, I had all this data from Alaska saying the toxins are already present in the Arctic."
The subsequent study showed that while the toxins are present in Arctic mammals, it's not known yet if they are at levels that actually affect the health of the animals. However, the presence of the toxins means the potential for health risks is definitely there. That's what she and her team are trying to gather more data on now.
"My concern is, is it a growing risk? Are these toxins and harmful algal bloom species moving north with the warmer water and able to bloom more? If this continues, what is the health risk for marine mammals?" she wondered.
Past research with other species has shown that long-term exposure to domoic acid can have serious consequences for animals, which is why it's important to look at whales while there's the opportunity to do so, said Lefebvre.
Domoic acid is a neurotoxin, which means it interacts with the nerves in an animal's central nervous system. It's also an excitotoxin that overstimulates the system, which is why animals with domoic acid poisoning may have seizures.
In a 2015 study done by Peter Cook in California, he found that sea lions who had acute high-level exposure to the toxin to the point of having seizures can suffer permanent brain damage if they survive.
"(The damage occurred) particularly in the hippocampus, which is the memory center of the brain. It causes lesions there. There's a correlation between the size of the hippocampus, that means a reduction of it, and spacial and memory learning deficits," said Lefebvre. "Basically, they have permanent spacial memory loss, which means it could affect their ability to migrate, to forage, to go back to locations they went before, probably to avoid ship strikes, all kinds of things."
Lefebvre is conducting studies using mice to look at low-level exposure that's not high enough to cause seizures and the results appear to be different.
"You do see learning deficits after a certain period of time, but then we're finding that those learning deficits go away if they're given a recovery period. That's brand new," she said. "We're trying to get that all put together and write it up but the gist is there certainly are long-term effects. When you get a big dose, it's a permanent effect. At low levels you can recover."
As the various studies move forward, including the analysis of data from the Barrow bowhead whale population, the team hopes to find out more about what the future holds for the animals in these regions, like the Arctic, that have been exposed to the toxin.
"That's what we want to monitor and track and it's a scary situation with the changing environment," she said. "You think about these majestic, long-lived animals that have been potentially living there for a hundred years. That means in a hundred years they haven't had a poisoning event. So, what happens if levels get high enough all of a sudden in a couple of years? That could have profound effects on that population."
This story first appeared in The Arctic Sounder and is republished here with permission.
Alaska Dispatch Publishing