Sometimes new parents get lucky. They get “easy” babies. Young sunflower sea stars are the fussy kind—but their adoptive parents are managing.
At a laboratory in the California Academy of Sciences, senior biologist Riah Evin tends to several glass candy jars of seawater in which tiny, translucent larvae twirl like flecks of snot. They must be constantly stirred, Evin and her colleagues have found, just like they would be in ocean currents. If not, the larvae sink to the bottom and crush each other, and with them a great hope for restoring West Coast kelp forest ecosystems. “We’re culturing a really devastated species with pot stirrers and candy jars,” Evin says. “But it’s working, and it’s working really well.”
Sunflower sea stars (Pycnopodia helianthoides, often referred to as “pycnopodia” by researchers), were once the most ubiquitous sea star on the West Coast, ranging from Mexico to the Aleutian Islands. They were key predators in the kelp forest food web—until 2013, when a wasting disease arrived that wiped out 94 percent of their population. To figure out how to raise sunflower sea stars in captivity and eventually restore their populations in the wild, a consortium of researchers banded together as the Pycnopodia Recovery Working Group. The California Academy of Sciences, also known as Cal Academy, and nine other aquariums in the U.S., including the Birch Aquarium in San Diego, Cal State’s Long Beach Aquarium of the Pacific, the Sunflower Star Laboratory in Monterey Bay, and the Cabrillo Aquarium in Los Angeles, are all currently raising pycnopodia. The Academy’s sunflower sea star program is being supported in part by private donations and, as of this fall, $1.8 million from the U.S. National Oceanic and Atmospheric Administration, as part of the Pacific Coast Ocean Restoration Initiative. (That’s an ambitious new collaboration, funded by grants from the Inflation Reduction Act and Bipartisan Infrastructure Law, that is working up and down the California coast.)
“We had really good success in the first six months of this larval program,” says Academy aquarium curator Kylie Lev. “More than I genuinely thought was possible.”
This story is part of Wild Billions, a Bay Nature project exploring the impact of big federal money on Bay Area nature.
Ocean big picture: Read about the Pacific Coast Ocean Restoration initiative, a many-tentacled new $18M gambit to save struggling coastal ecosystems in California.
A sea urchin’s worst nightmare
Like Roombas with over 20 arms teeming with suction cups, adult pycnopodia scuttle across tidepools and kelp forests in search of prey, brandishing digestive juices. Pycnopodia eat snails, clams, crabs, sand dollars and more. They can gobble up a sea urchin, spines and all, digest its flesh, and spit out a clean, spineless shell. “They’re one of the biggest, fastest sea stars in the sea,” says Sarah Gravem, a marine ecologist at Oregon State University. “They’re like an extra-large pizza at their biggest.”
Not so long ago, you could count on pycnopodia to devour purple urchins and keep them from eating too much kelp. But about a decade ago, the mysterious wasting disease began plaguing 20 different species of West Coast sea stars, right around the time that a marine heat wave known as the Blob struck. Affected sea stars melted into mush. Pycnopodia were hit particularly hard. An estimated 4.75 billion sunflower sea stars perished along the West Coast. They all but disappeared in California, Oregon, and most of Washington. “It was the biggest epidemic we know of in the ocean, ever,” Gravem says.
In the absence of their primary predator, purple urchin populations exploded. Since then they have mown across the sea floor unhindered, leaving urchin barrens where kelp forests once flourished. “Kelp forests do so much for our local ecology,” says Evin. “They protect our coast, they give us food, and they’re dying.”
A mini ocean menagerie
A big milestone in pycnopodia restoration came on Valentine’s Day this year. Two adult sunflower sea stars at Birch Aquarium in San Diego spewed millions of reproductive cells into the water. A fraction of these cells bumped into each other and fertilized—a successful spawn that received much fanfare. Cal Academy scientists and other members of the Pycnopodia Recovery Working Group got larval offspring from that trailblazing pair, and have been experimenting through the rollercoaster of pycnopodia parenthood. Different aquariums’ staff are tinkering with different environments and feeding regimens, hoping to understand sunflower sea stars’ life cycle well enough to successfully raise them in captivity.
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Part of the difficulty is that baby pycnopodia are not just little versions of the adults. The sunflower sea star’s life cycle is mysterious and finicky: larvae look nothing like their parents, and undergo four different stages before metamorphosis. In the wild, they start out only about the size of a grain of sand and drift as plankton in the open ocean, eating other larval creatures. It’s a challenge for scientists to mimic ideal conditions—partly because studying miniscule wildlife in the open ocean is difficult, and partly because the larvae require different species and sizes of live food at every developmental stage. So the Academy team must culture a miniature ocean menagerie, including the larvae and juveniles of bat stars, ochre stars, and purple urchins, as well as phytoplankton—each with their own preferences in terms of temperature, water quality, stirring speed, food density, and how tightly packed together they are.
Once pycnopodia larva settle down and metamorphose into juvenile stars, they look much more like their adult counterparts, with radial symmetry, undulating frilly gills covering the tops of their bodies, suction-cup legs teeming all over their undersides, and tiny eyeballs on the end of each new arm. Far more of the Academy larvae have survived to this stage than Lev and Evin expected. Their charges have now graduated from jars into shallow tubs. But at this stage, there’s a new risk: If any of the juveniles grow bigger than the siblings around them, they have a tendency to become cannibals. “We’re still trying to better understand if it’s a food availability and density thing, or if it is just ‘my neighbor tastes better,’” Lev says.
As of this fall, the largest juvenile sunflower sea star at the Academy was about the size of a dime and had 11 arms. It will have to feed and grow for years before it can reach the legendary proportions of its adult counterparts, which can grow as many as 26 arms. Once the current pycnopodia have grown big enough, Lev and Evin plan to display them in the museum’s public aquarium. Depending on another successful spawn from the Working Group, they also hope to raise another round of larvae.
“Everything that we’re learning here will be applied to future generations,” says Lev.
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But … will it work in the wild?
Releasing captive-raised sea stars into the wild in California is still many years away, according to Lev. The population currently being raised are direct siblings, and not genetically diverse enough for reintroduction. And all this work is based on the hope that introduced pycnopodia will keep urchin populations in check—either by eating them, or by scaring them away—which is not a given, says Gravem, the Oregon State ecologist.
That’s why, last summer in ocean waters off Sitka, Alaska, Gravem’s team set out living-room-sized underwater enclosures called “pycnopodia pens.” In each one, they placed some urchins and three wild sunflower stars, to see how the urchins would react. In the first version of the experiment, the wily, athletic sunflower stars clambered right up and out of the pens and escaped. This time around, the pens had pigeon spikes around the top to keep the research subjects inside. Gravem’s research team has been counting how many urchins the sunflower stars devoured over two months, and how much kelp the urchins ate when pycnopodia lurked nearby; the scientists are currently analyzing this summer’s results.
“How important are these sea stars, really?” asks Gravem. “We can’t just put the hypothesis out and then go spend all that money based on a hunch.”
