Over the course of several seasons, dead seabirds have been found on coastlines all over the Bering Strait region, most of them emaciated.
Scientists don’t know why the birds are starving, and they say they don’t have enough information yet to determine a definitive link between these specific bird die-offs and toxins created by algal blooms.
“There’s not a lot of information about direct effects of these toxins on birds. We know that they can be harmful. But as far as trying to understand exactly how they act in the body and at what levels is really challenging.”
That’s Caroline Van Hemert, a research wildlife biologist with the U.S. Geological Survey. She says the USGS started testing for algal toxins, specifically saxitoxin and domoic acid, in birds after the last few consecutive years featuring die-off events, going back to a 2016 common murre die-off in the Gulf of Alaska.
Van Hemert shared her preliminary findings during a workshop in Nome this week, from one particular die-off that affected about 1,500 birds. She says most of the dead birds were northern fulmars, shearwaters, and kittiwakes located between the Aleutians and Point Hope.
“And so we were able to get a sampling of fulmars, that was the largest sample size we had of 16 individuals, and then a couple of common murres, a few shearwaters, one storm kestrel, and one puffin. And what we found was that the saxitoxin was detected only in fulmars, so of those other smaller numbers of individual birds, we didn’t detect any saxitoxin. There was no domoic acid that we were able to detect in any of the individuals.”
Van Hemert mentions that saxitoxin was detected in almost 90% of the dead northern fulmars tested and has been found in other sampled birds from past die-offs. For this particular study, she says the data suggests saxitoxin could have played a role in the birds’ deaths.
According to Van Hemert, the USGS doesn’t yet know what the baseline level is for saxitoxins found in healthy seabirds. Therefore, it’s harder to know at what concentration the birds are negatively affected by saxitoxin.
When looking specifically at seabirds who died in 2018 in the Bering Sea and Chukchi Sea regions, though, as well as Kodiak and Cook Inlet, test results show unquantifiable levels of saxitoxin.
Matthew Smith, a geneticist with USGS, says because of this variability, the agency can’t rule out other possible explanations for the starving birds, like a lack of available prey.
“There hasn’t been any causative association for algal blooms to these seabird die-offs, and that’s what really sparked this research to begin with and what we’re doing. So, we don’t have direct evidence that these birds didn’t just starve to death. And there’s a lot of work going on with some other folks at the USGS who are working on the forage fish aspect. And there’s a lot of anomalies from 2015-2016 during that blob, Pacific heat/hot water event.”
Van Hemert and Smith say they don’t have enough information about forage fish in this instance to determine if it was a prey-related issue that caused the birds to starve instead of toxins from algal blooms. Regardless, Smith says the USGS is unable to specifically link saxitoxin or domoic acid to these die-offs.
Scientists say finding toxins in seabirds is not new; they’ve been living with its presence for years, just like other marine life in Alaska, but how much they can handle before it starts to harm them is currently an unanswered question.
So, the agency plans to continue testing to find more answers. They’ve recently used an experiment with 12 mallards to test what the lethal dose of saxitoxin in birds is, and where in the body the toxins would show up. According to Smith, after 48 hours, the toxins were not found anywhere in the surviving birds, indicating the toxins leave their bodies relatively quickly.
Smith says when the mallards’ blood didn’t contain any traces of the toxins, he was surprised.
“Some of these birds died in under 15 minutes, and the longest was about an hour, and what we found was most of the saxitoxin was sequestered to the GI tissue. There was very little found in muscles, kidney, and liver, lung tissue. The small intestine, large intestine, and GI content had high to very high values for toxin. And there was no toxin detected in the blood, or brain, or heart tissue.”
It is Van Hemert and Smith’s hope that with more testing like this, and more data from dead seabirds, they can identify exactly what is causing most of these avian species to starve in Western Alaska.