Friday Harbor Labs is working to turn the tide against fast-moving wasting disease and return environment-protecting sea stars to the Salish Sea.
Updated July 29, 2025
The quiet, cluttered, colorful lab on the shores of Friday Harbor hosts sunflower sea stars of every stage of life. Parent stars, bigger than human babies, bathe in wooden boxes. Their offspring, larvae hardly larger than dust, swirl in white buckets. Young stars latch onto the walls of clear containers, and one- and two-year-olds cuddle in bins on the racks.
It’s the world’s first sunflower star rearing program, and about a year has passed since the reintroduction efforts began. Funded by the Nature Conservancy, divers reintroduced 10 one-year-old stars and 10 two-year-old stars into the water right offshore last summer. This summer, those divers found stars from both age classes, said Willem Weertman, a researcher at Friday Harbor Labs, a University of Washington field station.
None of these stars were injured, none diseased, he said; all healthy, all growing.
Many of them were found near eelgrass beds. That means eelgrass is possibly serving as a nursery, shrouding them from predators. The stars then protect the eelgrass from critters that eat it as well.
It’s a small — yet scalable — experiment, one of many steps to recover a population almost entirely wiped out 10 years ago.
Sunflower stars once thrived here, with estimates reporting one star every 10 square meters across the entire Salish Sea. From 2013–2015, a mysterious pandemic known as sea star wasting disease eliminated nearly a billion of them in the sea alone and almost five billion along the West Coast, Weertman said.
Now, divers are lucky to see one. With a handful of researchers and a few stars at a time, this small lab on San Juan Island is attempting to turn the tide.
And it’s making progress. Nature Ecology and Evolution will soon publish a paper by lead author Melanie Prentice and co-author Jason Hodin, senior research scientist at Friday Harbor Labs. The report, which analyzed stars bred by this lab, will focus on the pathogen that caused the fast-moving, destructive disease.
While the disease is still little-understood, it’s becoming clearer, Weertman said. Researchers now think it may be bacteria transmitted via touch and impacts the stars through the skin. [Ed.: Clarified status of findings.]
Following the pathogen study, the next step is a molecular test for the disease so divers can go out and test the new population.
“We don’t really have a good understanding of what’s going on with these in the wild,” Weertman said.
As for why the reintroduced stars seem to be doing well, Weertman is left to guess. He said it’s possible these new stars have been chronically exposed to low doses of the disease. They might be more resistant than previous generations.
The sea urchin threat
With a range from Alaska to Baja, sunflower sea stars are temperature tolerant, resistant to climate change.
The only thing that seems to kill them is sea star wasting disease, Weertman said, and it killed nearly all of them.
“They were a dominant predator across the entire coast,” he said, eating sea urchins, crabs and snails among a broad diet.
The major impact of this loss, so far, has been the increasing rule of sea urchins, Weertman said. Urchins destroy kelp forests and can live hundreds of years. Today, the west side of San Juan Island has become overrun with them.
This poses a large threat to kelp, which bolsters fish populations and, as a result, whales and people.
Urchins are menaces to much of the ocean, Weertman said. Even after they destroy all the vegetation, they don’t die from lack of food. They lay dormant and return when the vegetation grows back.
Before the sea stars were wiped out, they ate an estimated three to four billion of these urchins a day, he said.
As such a dominant species, they were understudied prior to the disease. They eat all kinds of things, not just urchins, and scientists may never understand the full impact of their loss.
“Almost certainly there have been massive changes in just the ensemble of the entire ecosystem related to the loss of sunflower stars that haven’t been noted,” Weertman said.
The stars come in varying combinations of purple, orange, red, pink, yellow and brown and typically have 16 to 24 arms, compared with the usual five found in other sea star species.
“You can think of them as cleaners, predatory cleaners,” Weertman said. “They eat herbivores and little things.”
In the lab’s bins, toddler-aged stars cuddle, interlocking these arms.
Why do they do it? “Unfortunately you can’t ask them,” Weertman said.
Seeing them embrace each other, to the layperson, it’s easy to anthropomorphize and difficult to think it doesn’t have a social component. Whatever the reason, it’s likely why the species was hit so hard by the disease.
“In my head there was this chain reaction of stars touching each other all along the coast and that really rapidly transmitted the disease,” Weertman said.
Rearing the stars
In early February, researchers inject a hormonal peptide into the parent stars to help them spawn. One sunflower star produces millions and millions of offspring, and the team works to avoid inbreeding and promote biodiversity.
When the stars are larvae, they eat larvae of other species, Weertman said. The food larvae is kept in flasks filled with bubbling liquid — one pink, one green.
When the sea stars have graduated from larvae, but are still tiny, researchers feed them baby urchins until they are two millimeters, the size of a grain of rice. At that point, they can transition them to a diet of clams purchased from local hatcheries.
Once big enough, the sea stars eat barnacles.
While the process is scalable, it won’t be enough on its own to repopulate the billions of estimated stars throughout the Pacific.
But scientists have already seen some success.
A coordinated, multi-institutional initiative in southeastern Alaska, which began with a captive rearing program in 2019 modeled off of Hodin’s lab in Friday Harbor, has seen some recovery, Weertman said. The program’s vision is to restore sunflower sea stars to their historical range by 2030.
Researchers have also seen some recovery along Saratoga Passage, Weertman said, but no major progress has been made around San Juan Island or a large part of Puget Sound.
Likely, the sea stars need some population density before they start reproducing in a major way on their own, he said. But he has hope.
“It’s a big ocean,” he said, “and these stars can move fast enough that they could move across the harbor in a day.”
A couple of scientists, a small population of stars and a bit of hope in a sea of unknowns …
“Obviously we aren’t going to be able to breed a billion stars, but the stars are really good at reproducing,” Weertman said. “If we can get them back to good densities in a few locations and get breeding populations out in the wild, we think you could kickstart the recovery.”
— By Sam Fletcher
Also read in Salish Current:
• “Science denialism and the bright extinction of killer whales,” May 23, 2024
• “To the rescue: saving lives, taking action on plastic trash in the Salish Sea,” Sept. 14, 2023
• “Researchers, growers face the challenge of acidic ocean water,” Nov. 3, 2022
• “Devastating wasting illness of influential, iconic sea stars still a mystery,” Oct. 21, 2022