For the last decade, California’s offshore seafloors have been missing a massive, colorful predator that keeps kelp-munching sea urchins in check.
The sunflower sea star is a big starfish — more than 3 feet across — that roams the ocean floor in orange, yellow and purple. These invertebrates can grow as many as 24 arms, and they’re impressively fast, carried across the seabed by thousands of noodle-like tube feet.
When a mysterious disease nearly wiped out sunflower stars in 2013, armies of purple sea urchins devoured almost all of Northern California’s iconic kelp forests. But sunflower stars may once again dot the seabed, thanks to pioneering projects to grow them in labs across California, including several in the Bay Area and Monterey County.
Behind a closed exhibit and through a locked door at the California Academy of Sciences in San Francisco, biologist Riah Evin has raised 137 sunflower stars in salt-water jars and tubs.
Recently, Evin peered into bins where small, pink-hued starfish munched on bits of herring. She carefully removed an eight-armed sea star juvenile just 3 inches wide. It was one of 11 million sunflower star embryos she started experimenting with in February.
“These are the survivors,” she said. “That’s way better than I had hoped for.”
The starfish will eventually be available for the public to see in an exhibit at the museum, offering sightings of a fascinating predator that has become virtually extinct on the California coast.
More important is their scientific value. Researchers in this lab and others are rearing sunflower stars from infancy as part of an international effort to conserve and study them, boosted by an $18 million grant this year from the National Oceanic and Atmospheric Administration. In 2020, the sea stars were deemed critically endangered globally, and a conservation roadmap two years later called for more labs to raise and protect them.
If scientists can answer key questions about genetics and the disease that pushed them toward extinction, stars like Evin’s might someday be released back into the Pacific Ocean. The hope? That their return would curb purple urchin populations and allow critical kelp forests to regrow.
“There’s a lot of promise in where the research will head,” said Andrew Kim, a research scientist at Moss Landing Marine Laboratories on Monterey Bay who is also growing sunflower stars. “I’m very hopeful.”
Roughly 6 billion sunflower stars have died in their range from Baja California to Alaska since 2013, due to an ailment known as sea star wasting disease. In their absence, purple urchins surged in population and chewed through entire undersea forests of bull kelp, which are the foundation for a rich marine ecosystem. Scientists estimate that 96% of Northern California’s kelp forests have vanished since then.
These underwater “redwoods of the ocean” are swaying habitats for all manner of marine life, from rockfish to abalone. South of the Bay, they’re also the dwellings of sea otters, which in turn protect kelp by feeding on urchins, cracking their shells and slurping their uni, or gonads.
Experiments are underway to “seed” kelp forests and hand-remove thousands of urchins from coves in Sonoma and Mendocino counties. While these projects have had success on a small scale, case studies suggest that the return of natural predators like sunflower stars — and potentially sea otters — could broadly restore kelp forests.
There’s little purple urchins can do to escape the maw of a roving sunflower star. They’re quickly overtaken, and the sea star extends its stomach outside of its body to digest its prey. When the star is finished, it expels a shell that’s picked clean.
Yet scientists like Evin are only beginning to understand the sunflower star’s many intricacies. The disease that pushed them toward extinction still isn’t well understood, even though researchers have been working to solve that puzzle for more than a decade. Only six adult sunflower stars are held in labs in California, and researchers are still experimenting with ways to breed them.
On Valentine’s Day this year, Evin found herself at the Birch Aquarium in San Diego to do just that. Before her was one male star and one female. Working with other scientists, she administered a spawn-inducing hormone to the male and began to wait. Hours ticked by.
“And then we started playing Barry Manilow,” she said.
The male and female released billions of sperm and eggs, which fused to form embryos. Those in turn developed into floating larvae no bigger than specks. The Academy of Sciences was allotted roughly 11 million larvae, and the rest were divvied up to other aquariums and universities, including the lab at Moss Landing.
Back at her lab in San Francisco, Evin began experimenting with ways to create a suitable habitat. Surprisingly, she landed on a simple technique: They thrived in a jar of spinning salt water set in motion by an automated pot-stirrer you’d find at a kitchen appliance store.
The larvae soon metamorphosed into baby stars with five points. Although they’re cute, Evin knew that young stars are cannibalistic — they’ll devour each other unless there’s ample other food. She experimented with giving them different foods, such as urchins and prawns, and observed their feeding habits. She’s set to analyze the data for that experiment.
But it’s clear that some stars fared better than others. One star had gobbled up hundreds of its siblings, and Evin nicknamed it “Legion.”
“There’s a little bit of a ‘Thunderdome’ going on,” she said.
Meanwhile, research scientist Elora López-Nandam is extracting DNA from the young sea stars for an inquiry into their genetic makeup. That’s important work. It’s still unclear why millions of sunflower stars survived the wasting disease epidemic from Oregon to Alaska, while California and Mexico’s populations were almost eradicated.
The disease remains a top concern for the California Department of Fish and Wildlife, said Ian Kelmartin, an environmental scientist with the agency. For that reason, he couldn’t say when scientists might obtain state approval to place sunflower stars back into the wild.
“What we don’t want to do is reintroduce (the disease) to recovered sea star populations,” Kelmartin said. “To get a handle on that, we need to understand what the disease is.”
For the time being, then, sunflower stars will call labs like Evin’s home. That’s comforting to Ashley Kidd, a project manager with the Sunflower Star Lab in Moss Landing. But it’s also bittersweet in the era of changing climates and staggering losses in biodiversity, as species blink out across the globe.
“Zoos and aquariums are living arcs,” she said. “It is tragic in a way, but very useful if you can use it in time.”