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It's Summer, And That Means The Mysterious Return Of Glacier Ice Worms

Jul 13, 2021
Originally published on July 13, 2021 12:24 pm

High up on Mount Rainier in Washington, there's a stunning view of the other white-capped peaks in the Cascade Range. But Scott Hotaling is looking down toward his feet, studying the snow-covered ground.

"It's happening," he says, gesturing across Paradise Glacier.

Small black flecks suddenly appear on the previously blank expanse of white. The glacier's surface quickly transforms as more and more tiny black creatures emerge. The ice worms have returned, snaking in between ice crystals and shimmering in the sun.

These thread-like worms, each only about an inch long, wiggle up en masse in the summertime, late in the afternoon, to do — what? Scientists don't know. It's just one of many mysteries about these worms, which have barely been studied, even though they're the most abundant critter living up there in the snow and ice.

Scientists aren't sure why the segmented worms, each less than an inch long, wriggle to the surface of the glacier late in the day, though they think it may be to feed or to soak up the sun's rays.
Scott Hotaling

Billions and billions of inch-long black creatures

"There are so many," says Hotaling, a researcher at Washington State University. An estimated 5 billion ice worms can live in a single glacier.

"From where we're standing right now, I can see, five, six, 10 glaciers," he says. "And if every one hosts that density of ice worms? That is just a massive amount of biomass in a place that is generally biomass-poor."

There are more mysteries than there are solved things with ice worms. - Scott Hotaling, glacier biologist, Washington State University

For a long time, he says, biologists have written off high-altitude glaciers such as these as basically sterile, lifeless places. Ice worms, however, show that this fragile environment — where the glaciers are vulnerable to climate change and are retreating — is potentially far more complicated.

"If you were going to put a biological mascot on glaciers of the Northwest," Hotaling says, "it's an ice worm."

And yet, with the possible exception of the annual Cordova Iceworm Festival in Alaska, these bizarre worms have generally been either ignored or treated as a mere curiosity.

The National Park Service's visitors center near Paradise Glacier, for example, has a nice display on alpine wildlife, Hotaling says, "and there is somehow nothing about ice worms. And it is a source of frustration for me."

He admits that it bothers "probably no one else that comes here." Many people who hike, ski or work on these mountains have never seen an ice worm despite their abundance, partly because the beasts only come to the surface at certain times of the year, at certain times of day.

Though they're called ice worms, the creatures Hotaling (right) and his colleagues study on the glaciers of Mount Rainier can't handle the slightest bit of freezing. If temperatures dip even slightly below zero degrees Celsius (32 degrees Fahrenheit), Hotaling says, the worms die.
Peter Wimberger

''Damn it, they're real!''

"They're very obvious once you notice them, but it's so beyond your expectation, when you're in a glacier environment, that there will be worms," Hotaling says.

His colleague Peter Wimberger of the University of Puget Sound says that he got interested in the worms years ago when a student said he wanted to study them. Wimberger thought the guy was pulling his leg and that it was some kind of prank. "He realized I didn't believe him," Wimberger says, "and all of a sudden he pulled out this little, small stack of papers and he said, 'Damn it, they're real!' "

The stack of scientific papers was small because only a half-dozen or so researchers have ever studied the worms, Hotaling says.

The worms shrug off shockingly high levels of harsh ultraviolet light, according to Hotaling, which is a good thing, because the summer sun on the treeless, snow-covered mountainside can be intense.
Scott Hotaling

They thrive in a glacier but die if they freeze

No one knows how these worms survive the harsh winters, or how far they burrow down into the snow. Hotaling thinks that at times they likely live under 30 feet or more of snow, down where the yearly seasonal snow meets the older snow of the glacier.

Winter may be the best season for them and a time when they can increase their energy stores, Hotaling says, because the worms are fatter when they first come out, early in the summer, than they are later on.

The worms are thought to eat snow algae and bacteria, but they may not need much. "I've kept them in my fridge, in my home, for physiology experiments, for a year or more, without adding anything to their system, and they're fine," Hotaling says.

Actually, though, he notes that he's not sure if those particular worms survived the year, or if they reproduced themselves. That's because ice worm reproduction is also a big black box.

"Early in the summer you tend to see more smaller ice worms, suggesting that at some point before that, their little eggs hatched and baby ice worms popped out," Wimberger says, "but we don't know."

What is clear, from lab tests, is something pretty surprising for an animal that has "ice" in its name: "They can't handle even the slightest bit of freezing," Hotaling says.

The worms may live at zero degrees Celsius (32 degrees Fahrenheit), but if temperatures dip even slightly below that, he says, the worms die.

Ultraviolet light doesn't faze them

Other tests, meanwhile, show that the worms shrug off shockingly high levels of harsh ultraviolet light, according to Hotaling. Which is a good thing for them, because the summer sun on the treeless, snow-covered mountainside can be intense. Whatever drives them up to the surface, they seem to wait until the later hours in the day when the sun isn't as unforgiving.

"I actually think they are coming looking for the sun a bit," Hotaling says, "because they want to have some of that heat energy to drive their biochemical reactions."

Hotaling sets up a wildlife camera. The natural history of ice worms and their predators, only now coming to light, underscores that the fragile environment of retreating glaciers is potentially far more complicated than first thought.
Nell Greenfieldboyce / NPR

Hotaling, Wimberger and a grad student — Jordan Boersma — have worked together to set up wildlife cameras around Paradise Glacier this summer. They want to understand to what degree wildlife uses these glaciers — and rely on ice worms for food.

Already, the researchers have spotted birds chowing down on ice worms. Those known to peck at worms include gray-crowned rosy finches, American pipits, common ravens, horned larks, semipalmated plovers and snow buntings.

Boersma says they want to know "if alpine nesting birds use them to provision their nestlings and if that's an essential part of their life history."

The birds may have an impact on the ice worms' natural history, too. Genetic research shows that ice worms may have traveled long distance from Alaska to Vancouver Island, perhaps by sticking onto the feet of migrating birds and hitching a ride.

A gray-crowned rosy finch catches an ice worm.
Scott Hotaling

So many basic questions remain unanswered. "There are more mysteries than there are solved things with ice worms," Hotaling says.

He even wonders if ice worms might affect how fast a glacier melts, because their black bodies must absorb heat. It's known that the presence of dark-colored glacier algae can speed melting, and ice worms clearly change the surface of a glacier.

"What goes away when a mountain glacier is lost? I don't think we have a good answer to that question," Hotaling says. "Ice worms are an extraordinary example of a bit of biodiversity on our planet that most people don't know about. And in this case, of Seattle and the Northwest, it's in the backyard of millions of people."

Copyright 2021 NPR. To see more, visit https://www.npr.org.

STEVE INSKEEP, HOST:

We take you now high into the mountains of the Pacific Northwest. It's a good season to stroll on a glacier, wouldn't you agree? You can feel the cool air now. NPR's Nell Greenfieldboyce did just that, and she returned with a story of a tiny creature, an ice worm whose very existence is hard to grasp.

NELL GREENFIELDBOYCE, BYLINE: Mount Rainier in Washington is the tallest peak in the Cascade Range. Fortunately, to see ice worms, you don't have to go to the very top. We're going to Paradise Glacier - over 7,000 feet up. From the trailhead, it is a long upward slog through snow.

(SOUNDBITE OF SNOW CRUNCHING)

GREENFIELDBOYCE: Scott Hotaling has made this trek many times.

SCOTT HOTALING: Ice worms essentially changed my life from the first time I saw them.

GREENFIELDBOYCE: He's a researcher with Washington State University and a kind of ice worm evangelist.

HOTALING: I have no shame in promoting ice worms.

GREENFIELDBOYCE: He says many people who spend lots of time on Mount Rainier and other Pacific Northwest mountains have never seen one or didn't understand what they were seeing.

HOTALING: They're very obvious once you notice them. But it's so beyond your expectation when you're in a glacier environment that there will be worms.

GREENFIELDBOYCE: The worms only venture out onto the surface of a glacier at certain times, like late summer afternoons. Hotaling says these worms are the most abundant beast that lives up high on these mountains, at least when it comes to animals you can see with your eyes.

(SOUNDBITE OF SNOW CRUNCHING)

GREENFIELDBOYCE: Trudging along beside us is Peter Wimberger from the University of Puget Sound. He got interested in ice worms about 15 years ago when a student said he wanted to study them. Wimberger thought the guy was pulling his leg, that it was a prank.

PETER WIMBERGER: And he realized I didn't believe him. And all of a sudden he pulled out this little, small stack of papers, and he said, damn it, they're real.

GREENFIELDBOYCE: It was a small stack of scientific papers because hardly anyone has studied them. After some more hiking, Hotaling bends down and scoops up some snow.

HOTALING: Here's an ice worm.

GREENFIELDBOYCE: I would never have guessed that was a worm.

HOTALING: Yeah. Eventually, you get good at spotting them.

GREENFIELDBOYCE: It looks like a moving piece of thread, about an inch long, thin and jet black. It's wet, and its dark body sort of shimmers and glistens as it writhes in between ice crystals, going pretty intently and gracefully. Hotaling says finding one on the surface is a good sign.

HOTALING: That suggests to me that they're starting to come up.

GREENFIELDBOYCE: We keep going, ever higher. The sky is bright blue. We see other snow-topped peaks in the distance - Mt. Adams, Mt. Hood, Mount St. Helens. When we stop for breaks, I ask questions about ice worms; the answer is almost always the same - no one knows. Hotaling guesses they can live under 30 feet or more of snow, down where seasonal snow meets the older snow of the glacier. They may not need much to survive.

HOTALING: I've kept them in my fridge in my home for physiology experiments for a year or more without adding anything to their system, and they're fine.

GREENFIELDBOYCE: Winters here are brutal, but that may be when living is easy for ice worms because when they come out onto the glacier surface at the start of summer, they're actually fatter than they are at the end of the summer season. They're thought to eat algae and bacteria. But, again, who knows? And here's the most surprising thing about ice worms, which, after all, have ice in their name.

HOTALING: They can't handle even the slightest bit of freezing.

GREENFIELDBOYCE: Hotaling says the worms live at 32 degrees Fahrenheit, but lab tests he and a colleague did show that if temperatures dip even slightly below that, like just one degree, the worms die. Meanwhile, other tests show that the worms shrug off shockingly high levels of harsh ultraviolet light, which is a good thing for them because the sun up here is intense.

HOTALING: And I actually think they are coming looking for the sun a bit because they want to have some of that heat energy to drive their biochemical reactions.

GREENFIELDBOYCE: We cross over a ridge and onto Paradise Glacier.

HOTALING: Did you see them? It's happening. And so now you can start to see - like, you can just look out a little further, and you can sort of see them just dotting.

GREENFIELDBOYCE: Thousands and thousands of ice worms have appeared. As we watch, their numbers rapidly grow and grow until there's dark flecks everywhere on the snow.

HOTALING: There's no hint of them trying to blend into their surroundings.

GREENFIELDBOYCE: You don't want to step on them, but it's impossible not to. Hotaling thinks these worms must have some kind of impact on the world around them because a single glacier is estimated to hold more than 5 billion.

HOTALING: There are so many. Like, from where we're standing right now, I can see five, six, 10 glaciers, and if every one hosts that density of ice worms, like, that is just a massive amount of biomass that's in a place that is generally biomass poor.

(SOUNDBITE OF DIGGING IN SNOW)

GREENFIELDBOYCE: A grad student named Jordan Boersma shovel snow from some rocks and sets up a wildlife camera. It's one of several the researchers are putting up here to understand to what degree wildlife uses these glaciers. Already they've spotted birds like ravens and rosy finches chowing down on ice worms. The worms could be a critical food resource for some species. Hotaling points out that climate change is making glaciers like this one melt. This habitat is rapidly changing.

HOTALING: What goes away when a mountain glacier is lost? I don't think we have any real answer to that question.

GREENFIELDBOYCE: Ice worms might even speed a glacier's melting. Their bodies darken the glacier's surface, potentially making it absorb more heat. Hotaling thinks this is worth investigating. He says when it comes to ice worms, there are more mysteries than answers.

HOTALING: Ice worms are an extraordinary example of a bit of biodiversity on our planet that most people don't know about. And in this case of, like, Seattle and the Northwest, it's in the backyard of millions of people.

GREENFIELDBOYCE: And when they look at snow-capped peaks like Mt. Rainier, most don't realize they're gazing at the realm of the ice worm.

Nell Greenfieldboyce, NPR News.

(SOUNDBITE OF VUREZ'S "GLORIOUS CRYSTAL GLEAM (MMX2 - CRYSTAL SNAIL STAGE)") Transcript provided by NPR, Copyright NPR.