Reports of dead seabirds raise concerns of another die-off
The last few weeks have seen another alarming uptick in the number of dead, emaciated seabirds found washed up on the shores in the Bering Strait region. While the exact cause of the deaths is not known, the last few years have seen a number of disturbing marine changes that some scientists warn could indicate a lasting ecological shift, with huge implications for marine life and the people that rely on it.
Robb Kaler, a wildlife biologist at the U.S. Fish and Wildlife Service in Anchorage who oversees seabird reports, said the first reports of dead seabirds in the region came in early June. They started out small – two guillemots in Shishmaref, some shearwaters and a puffin in Savoonga – but then Gay Sheffield, the Nome-based biologist working for the Alaska Sea Grant program, did a survey of a 10-mile stretch of beach that turned up 33 dead birds: 7 puffins, 20 murres, 3 unidentified gulls, and 3 kittiwakes. Kaler also received unconsolidated reports from National Park Service and Department of Fish and Game staff.
The reports come after three years of unprecedented seabird die-offs, in which birds of many species washed up in significant numbers on beaches across Alaska, starved to death for unknown reasons.
Kathy Kuletz, another seabird biologist at the USFWS, said that so far the numbers have not reached the levels of large die-off, but that the uptick is a reason to be vigilant. Intact carcasses from Sheffield’s survey were sent to the U.S. Geological Survey’s National Wildlife Health Center in Madison, Wisconsin to test for disease and toxins, but results have not yet come back.
The region has had a number of strange die-offs in recent years, according to Sheffield, and the causes of these events often remain mysterious. In 2011, all four species of seals in the region suffered from an “Unusual Mortality Event” in which many lost their hair, developed sores and died. The cause of the event was never identified.
Then, in 2012, 2013 and 2014 reports of dead birds and mammals covered in oil caused the Coast Guard to set up its first unified command in the Arctic, but no responsible party was found.
In 2013, thousands of birds died on St. Lawrence Island in what was eventually identified as an outbreak of avian cholera, the first time the disease was documented in Alaska and the first time anywhere it was documented in seabirds.
The latest spat of seabird die-offs started in 2017, when birds of many different species were reported starved and washed up on beaches all over the state. The pattern continued in 2018 and 2019, and although 2020 appeared to be a better year at first, the recent uptick in reports is a concerning sign. Sheffield said that the greater extent of sea ice this year may have prevented dead birds from washing up earlier in the summer, and that observers are only seeing the full extent of the damage now that the ice has melted.
Seabird die-offs can be the result of a mix of factors. Infectious diseases wipe out colonies from time to time, and harmful algal blooms (HABs) can fill the food web with dangerous toxins. Either of these factors could cause a bird to starve, weakening it to the point where it can no longer eat enough to sustain itself, but the scale of recent die-offs suggests the chilling possibility that they could be the result of ecosystem changes at a much larger scale.
The North Bering Sea has historically been one of the most productive marine environments on the planet, as cold nutrient-rich water from the bottom of the Pacific is forced up near the surface in shallower Bering Strait. When the ocean surface ices over every winter, a garden of algae grows just underneath it, feeding a huge range of marine life when the ice melts. The heavy, briny water that separates out from the ice sinks to the bottom, creating a “thermal barrier” or “cold pool” that keeps the water cool even after the ice has melted and keeps warm-water species at bay.
Warmer water temperatures in recent years, however, and the accompanying absence of sea ice, have major implications for the marine ecosystem, Sheffield said. NOAA did a fishery survey of the North Bering Sea in 2010 that brought back 26,000 metric tons of pollock, a species common in the South Bering Sea that is usually kept out of the north by the thermal barrier. They surveyed again in 2017 and came back with more than 1 million metric tons. The results made them come back in 2018, and they found the thermal barrier between the South and North Bering Seas to be almost entirely absent. “Their jaw, you could just hear it, hit the ground,” Sheffield said. “In 40 years they’d never seen conditions like this. They couldn’t find the thermal barrier, there was none.”
This huge change has a cascade of ecological effects, many of which are not totally understood. Pollock and Pacific cod invading from the south eat the same small fish as many seabirds, perhaps reducing the availability of prey. Warmer waters may also make friendlier environments for harmful algae, or make birds more susceptible to disease. Necropsies from the National Wildlife Health Center in recent years have failed to pin the die-offs on any single cause.
One major barrier to understanding the die-offs is the complex network of state and federal agencies that oversee the research and management of marine life. Although seabirds are managed by the U.S. Fish and Wildlife Service, research on them is done by the U.S. Geological Survey. NOAA oversees the large-scale surveys that give the most data on the marine ecosystem, but they tend to focus on the more commercially active South Bering Sea, and much of the seabird reporting is done by local citizen scientists and organized by the nonprofit Coastal Observation and Seabird Survey Team, or COASST, which is based out of Washington state.
The COVID-19 pandemic has exacerbated the lack of data, as 2020 research grinds to a halt. For the first time in 40 years, NOAA will not be sending survey boats to either the South or North Bering Sea, and many annual surveys of seabird colonies elsewhere in Alaska have been cancelled as well. The lack of data is especially painful this year, as last winter’s relatively large ice cover may have partially restored the thermal barrier and repaired the ecosystem.
But was it enough?
“That’s the big mystery going into this year,” Sheffield said. “And now, because of the pandemic, all research is cancelled. We have no idea what’s going on. None.”
The most pressing aspect of the story, however, is the human dimension. Across the Bering Strait region, subsistence communities rely on seabirds and their eggs for food. Brandon Ahmasuk, vice president of Natural Resources for Kawerak Inc., said that the last few years have been especially hard on subsistence communities as this important resource has begun to vanish.
“All communities have been and still are heavily reliant upon harvesting birds and the eggs,” Ahmasuk said, adding that recent reductions in the harvest have been hard on people.
There are also ongoing health concerns about eating diseased or poisoned birds, and die-offs have made many communities alarmed that the birds they hunt may make them sick. Humans have been known to get sick from shellfish tainted by algae toxins, for example, and it is currently not known whether people can get sick from eating tainted birds as well. The fear of sickness puts additional pressure on people already in the midst of a public health emergency.
It is still not clear whether this year will see a major die-off on the same scale as previous ones, but Ahmasuk and Sheffield both emphasized the importance of remaining vigilant and reporting anything unusual. Getting intact carcasses to send to the National Wildlife Health Center is especially important, both to understand the cause of the seabird die-offs and its effect on people that rely on them.