Toxic algae may have played part in sea bird die off
That is the question that multiple federal and state agencies are trying to solve to get to the bottom of an unusual seabird die off of multiple species in the region during this summer and fall.
A definitive answer is still eluding scientists but clues are pointing in the direction that biotoxins from harmful algae in the Bering Sea may have played a role.
What we know
Sea birds washed up dead in large numbers on beaches near Nome, Gambell, Point Hope, Shishmaref and the Pribilof Islands this summer. Officials from the Beringia National Park on the Russian side of the Bering Strait also reported unusual numbers of dead short-tailed shearwaters, crested auklets, murres and blacklegged kittiwakes on the southern coast of the Chukchi Peninsula, Cape Chaplin and Inchoun Lagoon. The park director of the Beringia National Park emailed a correspondence to the Nugget detailing the dead birds and said, “It should be noted that there was an active migration of crested auklets and short-tailed shearwaters during the survey period [August 24 until Sept. 2] along the coast. Presumably these are weakened birds unable to obtain food.”
Nome subsistence hunter Austin Ahmasuk reported the occurrence of dead birds on Nome’s West Beach and described strange behavior of birds that seemed to struggle to survive. Of a blacklegged kittiwake he said, “It was acting kind of drunk. It was half-heartedly flying away, trying to dive and then didn’t.”
According to a September bulletin by the U.S. Fish and Wildlife Service, over 1,200 beached seabird carcasses, including northern fulmars, shearwaters and kittiwakes were counted in early August.
Gay Sheffield, Alaska Sea Grant agent in Nome, coordinated a regional effort to collect bird samples and to send them to the US Geological Survey National Wildlife Health Center. Results from necropsies of 21 birds revealed that the birds were emaciated and died of starvation and drowning, but the cause of their emaciated state was not clear. They were tested for infectious diseases like avian influenza and avian cholera, but those diseases were ruled out as the cause of death. USFWS Rob Kaler told the Nome Nugget in an interview that it was puzzling to see so many seabird species over such a widespread area be affected. “There seems to be something profound going on with the food web,” Kaler said.
The cause of the starvation has not been identified until several other pieces of the puzzle emerge.
An observation from a June cruise of the research vessel Sikuliaq offered a clue that hints to conditions favoring algal blooms: the ocean waters had unusually warm temperatures. Seth Danielson, UAF Chief Scientist on that cruise said, “In June we found water temps that were about 4 degrees Celsius warmer than normal.” The normal temperature on the ocean floor of the Bering Strait is usually around 0°C, or 32°F. “We measured 39°F,” said Danielson. Off the Yukon River, he said, ocean temperatures were warmer than 54°F. “That is incredibly warm for the first week of June,” he said.
Warming ocean temperatures have been linked to increases in harmful algal blooms.
Another piece to the puzzle came when Sheffield requested research cruises that occurred in the Bering Strait region to take ocean water samples if they observed dead seabirds.
During a July Norseman II cruise, a researcher did indeed observe dead seabirds near the Strait and scooped up a seawater to be tested.
UAF researcher Prof. Dean Stockwell at the Institute of Marine Science was on Sikuliaq in July and he, too, noticed sea birds dead in the ocean. He told the Nome Nugget that the water samples analysis revealed water containing Alexandrium tamarense, a PSP toxin producing dinoflagellate, which he explained is a little plant organism that – if triggered- excretes saxitoxin, which causes paralytic shellfish poisoning. Stockwell said the presence of Alexandrium was proven, but the toxicity of the water was not. So the seawater sample was then send to Southeast Alaska Tribal Ocean Research Lab in Sitka for toxicity testing. Not only did the tests show that the toxin was present, but also at higher levels than is normally seen in Southeast Alaska. Stockwell also said that the presence of Alexandrium in this region’s waters is not new, and has been documented with reports dating back to the 1970s.
As the Nugget reported on February 11, 2016, a NOAA Fisheries study found the presence of harmful algae toxins, including saxitoxin, in every Arctic marine mammal species to the surprise of researchers. The warming of the northern Bering Sea and northern waters creates new realities of algal blooms and possible toxins eaten by marine mammals. Very little research has been done on what levels are harmful to any of the marine mammals or seabirds.
Back to the birds. As the necropsies revealed that infectious disease was not the likely culprit, the researchers requested that stomach contents, muscle and livers from the birds would be sent back to the USGS Alaska Science Center lab in Anchorage for domoic acid and saxitoxin testing. Results were not given on request by the Nome Nugget as all research partners had first to be consulted, as of press time on Tuesday. However, according to a news bulletin at the National Park Service’s website, NPS scientists have also counted hundreds of bird carcasses and found walrus and whale carcasses on their surveys. Samples were sent in to labs. “Early results show toxic algae may have played a part in the die off,” the NPS website states.
As the results from the water samples became known, other clues surfaced to solidify the theory that algal toxins may have played a large role in the die off . This time, the discoveries involved a large number of walruses that were found washed up on the beaches from Cape Espenberg to Shishmaref and further west. LCDR Courtney Sergent with the US Coast Guard said that the Coast Guard MH-60 helicopters stationed in Kotzebue for the summer conducted eight flights in July, August, September and October to assist the Eskimo Walrus Commission, U.S. Fish and Wildlife Service, National Marine Fisheries Service and Alaska Sea Grant in surveying and conducting investigations on marine mammal carcasses along the Seward peninsula. A helicopter flight on September 9 resulted in the count of 21 walrus carcasses just east and west of Shishmaref, between Ikpek and Singeak, on the northern Seward Peninsula. These carcasses were first seen during a routine Coast Guard flight on September 5. On a flight on September 12 U.S. Fish and Wildlife Service law enforcement officer Mike Wade and two community members from Shishmaref, Vice-Mayor Stanley Tocktoo and Walter Nayokpuk, were transported to the carcasses in order to take samples from two of the deceased walruses to determine cause of death. On subsequent flights by other researchers with the National Park Service, the total count of walrus carcasses rose to 39. In addition to the samples taken from the washed up walruses that showed no obvious signs of having been harvested, a fresher samples from a harvested walrus was also sent to Wildlife Algal-toxin Research and Response Network in Seattle, Washington.
And that is where a smoking gun was found: moderate to high levels of saxitoxin were found in all four samples. The one harvested walrus had very high saxitoxin levels. Testing is not over yet, meaning that the levels most likely will rise with further analysis. Kathi Lefebvre with WARRN-West was first to publish saxitoxin levels found in harvested walruses. The highest level she found levels was 240 nanogram/ gram. But a FWS technical report from 2016 found a high level of 1,161 ng/g saxitoxin in the intestines of a harvested walrus.
To put it in context, the federal US Food and Drug Administration seafood safety regulatory limit for human consumption of shellfish is 800 ng of saxitoxin per gram of shellfish to protect people from PSP. The amount of saxitoxin required to cause harm to a walrus is unknown.
Saxitoxin is a neurotoxin, which attacks the nervous system if ingested. PSP, or paralytic shellfish poisoning, occurs when people, or mammals, consume toxic shellfish, crabs or mussels. Symptoms include diarrhea, vomiting and in severe cases seizures, coma and death. Eating clams or mussels out of a harvested walrus or bearded seal stomach may carry the risk of PSP. So far, there were no reports of shellfish poisoning in the region.
What we don’t know
What toxic levels of saxitoxin that would be harmful to birds or walruses? Did low doses of algal toxins lead to sick birds that died from starvation and acting strangely because they were poisoned?
The Food and Drug Administration have levels established what levels of PSP are safe to consume in commercial shellfish. The same is needed to establish for subsistence marine mammal species and seabirds.
Sea Grant Agent Sheffield noted that this seabird wreck and the unexplained walrus deaths are just the most recent events of unsettling food security concerns to hit the region since 2011. Those events included sick seals, avian cholera, trichinella and oiled marine wildlife.
“Whenever there is a die off of seabirds or marine mammals, which are a food resource, there is cause for an investigation,” Sheffield said.
“The take away is, that we are still unsure of what caused the walrus or seabirds deaths, but we need to have monitoring, we need to remain vigilant, and communicate. We need to continue to call in when we see unusual deaths and behaviors in our marine wildlife.”
She added that more research needs to be done to establish at what levels harmful algal toxins impacts seabirds, walruses or other marine mammals.