Climate

Scientists want to bring back one of the ocean’s most unexpected predators

A photo of a sunflower sea star with a concentrated red center on a black background.

A 14-week-old sunflower sea star, about 5 mm in diameter, glides on its outsized tube feet at Moss Landing Marine Labs in California. This star is part of the “Cupid Cohort,” the offspring of stars that successfully spawned at Birch Aquarium on Valentine’s day 2024.

A starry night evokes magic, a sense of wonder or romance. But what about a starry sea? There are almost 2,000 species of sea stars or “starfish” worldwide, found across a range of habitats from tide pools to thousands of meters underwater. About a decade ago, the still-mysterious sea star wasting disease (SSW) had devastating impacts on sea star populations along the West Coast of North America. One of the hardest hit was the sunflower star, known as the cheetah of the intertidal zone for its speed and hunting prowess.

Ten years ago, the sunflower sea star population collapsed.

This loss has been detrimental to kelp forests because sunflower stars are voracious sea urchin predators. When more than 90 percent of the Pycno population disappeared following a wasting disease outbreak that began in 2013, the sea urchin population exploded. Now, these prickly grazers are mowing down the kelp en masse and creating extensive urchin barrens where there were once dense, flourishing kelp forests.

“The magnitude of [sea star wasting] — the geographic scale from Mexico all the way up into Alaska, and with over 20 species affected — there has never been anything (that we have any data on) that’s happened like that with sea stars before,” says Drew Harvell, a marine ecologist at Cornell University and Friday Harbor Labs who has been studying the outbreak from day one. Harvell published Ocean Outbreak in 2019, a book that details several ocean pandemics including the one that decimated sea stars.

This isn’t the first documented wasting event in sea stars — there have been large die-offs in the past, including one in the 1970s that impacted Heliaster kubiniji, but these events typically affected a single species over a smaller geographic extent.

“People who didn’t live through that 2013 to 2015 onslaught of the magnitude of that mortality really don’t fully comprehend it. … It was horrible,” says Harvell. “Having 10 different species of stars washed up on your beach suddenly was really dramatic.” It’s important “to preserve the enormity of that event,” she says.

In 2019, marine biologist Jason Hodin at the University of Washington’s Friday Harbor Labs was the first to try raising and studying sunflower stars (Pycnopodia helianthoides) in captivity. The Henry Doorly Zoo and Aquarium in Omaha followed suit, and now several other aquariums throughout California are raising the stars.

“Jason’s success with the captive breeding of the Pycnos really provided the fire that lit the whole Pycnopodia recovery program, because it showed a positive way forward and a real opportunity,” says Harvell.

Scientists and aquarists banded behind the sunflower star during the wasting event and put together the Roadmap to Recovery for the Sunflower Sea Star. Through an effort led by ecologist Sarah Gravem, the sunflower star was the first marine invertebrate listed as critically endangered on the IUCN Red List in August 2020.

But now, thanks to endeavors in the star’s historic home along the West Coast and beyond, the sea star may one day return to the ocean. It’s the beginning of a long restoration effort, but “there’s clearly an understanding or a passion [for Pycnos],” says Ashley Kidd, conservation aquaculture program manager at the Sunflower Star Laboratory.

The Association of Zoos and Aquariums now has a SAFE (Saving Animals From Extinction) sunflower star program aimed at saving these endemic — meaning they are found nowhere else in the world — stars.

To save a star 

After two years and hundreds of dives in California, the first adult sunflower star I ever laid eyes on was in a Boston basement. Four levels below ground in Harvard’s Museum of Comparative Zoology (MCZ), invertebrate collection manager Adam Baldinger opened white metal collection drawers to reveal almost two dozen dried Pycnos, ranging from button-sized to extra-large-pizza-sized stars, their dried arms curled at the tips.

There are more Pycnos in this Boston basement than there are living in aquariums in the state of California, where only five individuals remain.

Gazing upon a sunflower sea star is a strange experience. The genus name “Pycnopodia” literally translates to “dense feet” and the species name “helianthoides” means “sunflower-like.” They can have dozens of arms (and an uncanny ability to regenerate these arms) and grow to reach up to 3 feet wide. They seem like something out of a science fiction novel. Jen Burney, an aquarist at Aquarium of the Pacific, describes visitors as having a “fearful fascination” with the stars — they often don’t know what exactly they’re looking at.

“You really do need to think outside the box with starfish,” says Chris Mah, a research associate at the Smithsonian’s National Museum of Natural History. “You kind of have to think about them as aliens. … They’re pentameral things that have been around since the Paleozoic. … They move in a different time frame, they have a different metabolism, they eat differently,” says Mah. He studies all echinoderms but says Pycnos were one of the reasons he got into the subject in the first place. “People who study echinoderms do so because we revel in their weirdness.”

Baldinger gently unwraps the stars from plastic bags and arranges them on the table for me to photograph. Each star has a paper tag with neat cursive writing noting the specimen number, collector, and where and when it was collected. Some from Puget Sound date back to 1907.

One star stands out, both because it floats in a jar of ethanol and because the label notes it was collected in Monterey, California, a few miles from where I live, where sunflower sea stars are now functionally extinct.

The quest to bring sunflower sea stars back to California’s coast

The Heal the Bay Aquarium is small and tucked under the Santa Monica pier. Most people are here to ride the Pacific Park Ferris wheel, sip a milkshake, or buy a shell necklace from the famous pier that attracts 10 million visitors a year. But hidden below the pier is an aquarium filled with local species from the bay, including a small sunflower star that has been in their touch tank for almost 10 years.

Laura Rink, associate director of operations for Heal the Bay Aquarium, greets me with a friendly smile and ushers me inside, past undersea murals and aquaria housing moon jellies, sharks, and moray eels. It feels like stepping back into the ’90s in the most heartwarming way. In the back corner, near a tank of tiny California skates that look like grinning raviolis, is a pile of orange, purple, pink, and brown sea stars in a long aquarium with an open top. Above it is a colorful banner that reads “Touch Tanks.” Squished in the corner is a petite Pycno.

Before I can fully take in my first live sunflower star, the air is filled with excited shrieks as a group of local elementary school kids flow through the doors like a school of sardines. They are decked out in matching blue Superman T-shirts. Heal the Bay hosts about 15,000 Title I students every year, and for many of them, the beach and ocean are not familiar places. Some of the kids shy away from the stars, weirded out by their tube feet, funny texture, or the fact that they’re supposed to feed the stars chunks of dead fish with tweezers. Other kids dive right in, running between touch tanks with the excitement of seagulls surrounding a fresh catch of fish.

When the craziness subsides and I gently touch the petite Pycno, it feels like goo. It’s less calcified than many stars — instead of feeling leathery and tough like an ochre or bat star, it’s squishy. With its papulae, translucent white “skin gills,” out, it takes on an almost fluffy appearance, too. The Pycno in the tank glides up the glass. I place my finger next to one of its 19 arms and a few little tube feet reach out to investigate. I imagine these same stars scattered across the bottom of California’s kelp forest before wasting hit and they literally melted before our eyes.

As part of efforts to bring back the species from functional extinction in California, scientists and aquarists successfully spawned three Pycnos at Birch Aquarium in February this year.

“When the females started spawning, that was two years of work for all of us and we were all together,” says Jen Burney, codirector of the SAFE sunflower sea star program. “I didn’t want to cry in front of all my colleagues, but I think all of us were feeling very emotional about it.”

The sunflower star is only the second invertebrate to have SAFE designation; coral reefs were the first. The SAFE group is co-led by Burney and Ben Morrow from Omaha’s Henry Doorly Zoo and Aquarium.

“It’s our first year and we’re really hitting the ground running,” says Morrow. They’re now in the process of adding several more aquariums, including Georgia Aquarium, Oregon Zoo, Monterey Bay Aquarium, and others.

Following the February spawn in San Diego and a hand-off of endangered sunflower star embryos in plastic bags in a Burger King parking lot in Los Banos, California, stars are also now growing at California Academy of Sciences, Moss Landing Marine Labs (MLML), the Sunflower Star Laboratory, and Aquarium of the Pacific.

Andrew Kim, a researcher at MLML and a board member of the Sunflower Star Laboratory, has taken care of the sea star babies since the Burger King parking lot hand-off. But “babies” isn’t quite the right word – they really start as larvae, which look like tiny floating spaceships with waving arms. Sea stars metamorphose, kind of like a butterfly. In fact, most aquatic invertebrates and all echinoderms (sea stars, sea urchins, sea cucumbers, and sand dollars) start life as planktonic larvae before growing into the adult form we’re used to seeing.

Kim shows us the setup at MLML, and it’s hard not to get distracted as we wind through the wet lab filled with space-shuttle-like vats growing algae illuminated with pink and blue lights, aquaria full of abalone, tumble cultures of bull kelp, and tiny sea urchins. He leads us to the back, where he stops at a sky-blue saltwater tank big enough for a two-person cold plunge. It looks empty.

But as we stare into the tub, I slowly begin to make out millions of tiny dots. These little pink spots are the larvae’s stomachs, full of red algae from their morning meal.

Kim pipettes a few onto a slide so we can get a better look. Just like it’s hard to imagine a caterpillar becoming a butterfly, these clear, dancing larvae look nothing like sea stars, yet this is how every star will spend a few weeks of its life before settling.

When we return a couple weeks later, some of the larvae have metamorphosed. The settled stars look lace-lined, like snowflakes with an orange center. Under the microscope, their tiny tube feet suction to a single drop of water on the glass slide as they cruise around on their newly formed feet. They have five little nubs for arms, which will eventually elongate as they add upward of 20 arms.

For now, the hope is to share settled stars with other labs and aquaria outside of the four that got larvae from the recent spawn. Burney says another goal for this cohort is “to make sure technique-wise, we figure out what worked, what didn’t, and that in the future everyone is able to replicate this process.”

This initial cohort of stars won’t be released into the wild, but the long-term goal is to eventually put sunflower stars back into the ocean. “The big goal would be to outplant animals into the wild — that’s the pie-in-the-sky goal,” says Burney.

What raising future stars can teach us about saving other threatened species

The die-off happened so quickly that scientists have few pre-wasting Pycnos to study and also very few to use for breeding in California.

“We are limited in terms of historic California samples because there just weren’t that many [Pycnos] collected,” says Lauren Schiebelhut, an evolutionary ecologist at UC Merced. “They used to be super abundant, and nobody was worried about them until they totally disappeared and disrupted the kelp forest ecosystem.”

Schiebelhut recently published the reference genome for Pycnos. She and Mike Dawson, also at the University of California Merced, are trying to tease out a genetic component of SSW. They haven’t yet found a genetic marker for SSW but they did potentially find a way to determine the Pycno’s sex by looking at its chromosomes. It turns out the petite Pycno at Heal the Bay is a female, which is helpful for breeding since cryopreservation of sperm has been very successful and eggs from females are the limiting factor.

Schiebelhut adds that Pycnos are “a great model for thinking about other species in the future. … The diverse knowledge and experience that people bring to the table to tackle this problem has been really refreshing to see, and I think we’re going to need more of that in the biodiversity crisis.”

And there’s still hope for breeding Pycnos because inbreeding and genetic bottlenecks are not a problem yet. And sea stars can spawn. A lot.

“When you typically hear about an endangered species, it took a while to get there,” says Schiebelhut. “There may have been inbreeding before you’re all the way down to the last individuals. Sea stars are a totally different story. When they were hit in 2013, there were really large, successful population sizes with lots of genetic diversity, so the vast majority of that diversity is going to be contained in just a handful of stars.”

Because the wasting is relatively recent, the diversity hasn’t dramatically declined — yet, she says.

Meanwhile, scientists at Friday Harbor Labs in Washington and Hakai Institute in Canada are working to identify what exactly causes wasting so that they can test stars before releasing them into the wild or transporting them across state lines.

“We have three years of intensive experiments from Marrowstone Point’s fish virus lab [in Washington] — we don’t have the answer yet, but the consistency of the experiments gives us a great deal of hope that we’re going to be able to solve it,” says Harvell.

And this is a great sign for invertebrate conservation moving forward. This is the first conservation project for an invertebrate on the West Coast besides abalone, says Burney. “Invertebrates don’t get a lot of love when it comes to conservation, but that’s changing now, which is awesome because we’re finding it’s not just about the sunflower star, it’s about kelp forests. As we look at things a little more holistically, we’ll start to see more attention given to these other species that maybe aren’t the cutest but do play a really big role in their environment.”

As the sun disappeared into the fog at Moss Landing on the summer solstice, we visited the Sunflower Star Laboratory one more time to see the settled stars. They cruised around their clear containers, tube feet akin to clown feet, outsized for their tiny bodies, now sporting eight arms. It’s hard to imagine these tiny stars will grow up to be apex predators. Maybe someday, these stars, or their offspring, will again glide across the ocean floor and bring balance back to the kelp forests.

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