The Fate of the Stars
The Effort to Restore Pycnopodia to Our Coastal Waters
by Sarah Reith
Not that long ago, one of the reliable delights about a day at the beach was piles of rotten seaweed, buzzing with contented flies. On the way home, the car would smell like wet, seaweed-infused dog. That’s how you could tell that sunflower sea stars, pycnopodia helianthoides, were patrolling the waters nearby, devouring purple urchin or terrifying them into submission. Purple urchin have an insatiable appetite for seaweed, but the pycnopodia has an insatiable appetite for urchin. Adult pycnopodia can weigh up to 13 pounds. They have 16 - 24 limbs, spanning a meter and covered with thousands of tube feet. Compared to most sea stars, whose mobility level borders on the ornamental, pycnopodia are sprinters. They would run down purple urchin, dissolve their hard spines, and relish the uni inside.
Prior to 2013, they were so good at what they did, no one bothered to learn much about them. That year, a heat wave began to linger in the Pacific Ocean. Since then, an estimated 99% of the pycnopodia from Mexico to Alaska have succumbed to a wasting disease. The previously well-controlled purple urchin proceeded to eat 96% of the kelp, outcompeting other grazers like abalone. (Another beachgoer’s delight used to be plucking an abalone off a rock and eating it shoreside with friends. The large mollusks have faced other pressures too, including poaching, but those days are long gone.)
The waters off the Mendocino coast were hard hit by the kelp die-off. Animals that relied on the underwater forests saw their habitat dwindle to a few forlorn fronds. Remnant populations of wild pycnopodia do survive in the fjords and British Columbia, and there are regular sightings of a single charismatic juvenile off the Mendocino headlands, and scattered reports of others. But divers and tidepoolers report that purple urchin are the dominant life form in areas that used to swarm with variety.
A consortium of organizations has assembled a plan to restore the pycnopodia. In 2022, The Nature Conservancy published a “Roadmap to Recovery for the Sunflower Sea Star Along the West Coast of North America.”* An incomplete list of participating entities includes multiple state departments of fish and wildlife, as well as federal agencies, aquariums, and universities across the continent.
Much of the roadmap is a guide to acquiring basic knowledge of pycnopodia biology and genetics. Can they be inoculated against the wasting disease? How resilient are they? And can viable strains be bred in captivity?
Norah Eddy, associate director of the oceans program for The Nature Conservancy in California, is especially proud of the captive breeding program that’s flourished since the Roadmap was published. Though sightings in the wild are encouraging, she noted drily that, “We’re not doing back flips” about the occasional appearance of a celebrity sunflower sea star here and there. She maintains that the captive breeding program has resulted in “a ton of strides in epidemiology,” as well as an understanding of the inherent resilience of captive-bred specimens. Scientists at the Friday Harbor Labs at the University of Washington, led by Dr. Jason Hodin, have already released, and are now studying, two small cohorts of captive-bred pycnopodia, one in April 2023, and the other in August 2024. It’s a vital step on the way to a strategic reintroduction.
Closer to home, a few thousand tiny pycnopodia are swimming in carefully maintained quarantine at California Academy of Sciences’ Steinhart Aquarium in San Francisco. Some are barely flecks, and others fit in the frame of a fingernail. Urchin, oysters, and other kinds of sea stars are also being raised onsite to feed them.
Interest in the pycnopodia is gathering momentum. One Friday afternoon, Kylie Lev, a curator at Steinhart Aquarium and pycnopodia project lead, had back-to-back engagements with writers eager to meet her tiny charges. Spawned on Valentine’s Day at San Diego’s Birch Aquarium, they’ve graduated from floating passively in the water column and eating phytoplankton to settling on the bottom and catching prey. “They’re trying to eat us out of house and home right now,” Lev laughed, as a tiny pycnopodia perched on top of a tiny oyster, dining at a leisurely pace.
But apex predators don’t even need to eat herbivores to keep them in check. Eddy reported that, “Sea urchins are actually terrified of sunflower sea stars.” When a pycnopodia is on the prowl, she said the urchin behave like herd animals on the Serengeti, giving a wide berth to a hunting lion. “Recovering the pycnopodia will not only reduce sea urchins because the pycnos will eat them,” she explained. “It’s also going to change the way urchins behave…They are just out there doing whatever they want to do. They are eating kelp like crazy.”
Dr. Hodin has been breeding and studying sunflower sea stars at his lab in Washington since 2019. But this is science, where every data point has to be pored over and replicated and reviewed before it can be presented as fact. It’s unlikely that captive-bred pycnopodia will be deployed to restore order in the urchin barrens immediately. But stocking every tidepool is not the only metric of success. Lev insists that the effort is proceeding apace, “as long as you’re learning along the way and it has a positive impact in both data gathering and collaborative efforts.”
In the meantime, some humans are trying to fill in for the missing predator. Another consortium, with many of the same players that are working to restore the pycnopodia, is working on strategies to discourage urchin and restore the kelp forest. Tristin Anoush McHugh, the kelp project director with The Nature Conservancy, reported on efforts to clear urchin from two sites off Mendocino, one near Portuguese Beach and the other off Albion. “It’s been a great summer,” she declared, shortly after Labor Day. Since June, partners from Moss Landing Marine Labs, Sonoma State University, U.C. Davis, the Sea Urchin Commission, CDFW, the Ocean Protection Council and California Sea Grant, Reef Check and Above/Below had removed 52,910 pounds of purple urchin from a combined six acres from beaches in Big River and Albion.
But the tactics aren’t limited to suppressing the urchin. The Nature Conservancy is simultaneously leading tests in kelp enhancement methods, which, if successful, could lead to overall vegetative recovery in targeted restoration areas.
Scientists have also developed a technique that allows kelp to grow on strings from experimental modules above the seabed, where urchin can’t reach it. Two years after the first outplanting at Albion, Anoush McHugh exulted that much of this kelp “grew to adult, hit the surface of the ocean, created the sorus (reproductive) tissue, and has now released back into the system.” She described early signs of habitat restoration, from unicellular organisms creeping back onto the scene to the recruitment of rockfish, which is a valuable commercial species, especially with the closure of the salmon fishery. “We’re obviously still tinkering in the early days,” she conceded, “but everyone has been so on it, and we’re so excited by what we’re seeing.”
Eddy, too, is optimistic about the chances for both species. “We’re not talking about old-growth forests,” she said, acknowledging the climate change despair that sets in at some point during any conversation about restoring the environment. “Kelp are some of the fastest-growing organisms on the planet. Marine invertebrates have an amazing capacity to rebound when conditions are there … a lot is moving in our favor.”
The human effort to bring both species back from the brink is extensive. It includes raw labor, like clearing urchin and farming seaweed, and plenty of scientific innovation. The Association of Zoos and Aquariums is collecting reproductive cells from sunflower sea stars and cryogenically preserving them, to diversify the captive breeding program as much as possible. And nature itself could be poised to welcome the return of the missing species. Though the wasting disease is not yet fully understood, it appears to be strongly correlated with warming waters. The pending La Niña system is expected to cool the oceans, which could invigorate both pycnopodia and kelp.
It’s been over ten years since a day at the tidepools involved sightings of sea stars with a lot more legs than anyone else. Lev, the curator at Steinhart Aquarium, hopes to introduce her young ones to the public soon. And maybe someday, they will eat their way out of the house and find their way home to a welcoming sea.
Photos at Steinhart Aquarium and of the baby pycnopodia by Gayle Laird © California Academy of Sciences. Photo of sea star found in the wild by Nicole Ravicchio © California Academy of Sciences. Photo of group in sea cave by Sarah Reith.
Sarah Reith is a writer and nature enthusiast living in northern California.
*Find Roadmap to Recovery for the Sunflower Sea Star Along the West Coast of North America at https://www.researchgate.net/publication/366177598_Roadmap_to_Recovery_for_the_Sunflower_Sea_Star_Along_the_West_Coast_of_North_America
