Sunflower sea stars are nearly extinct, but scientists are growing them
12-30-2024

Sunflower sea stars are nearly extinct, but scientists are growing them

For nearly 10 years, California’s offshore seafloors have been missing a once-abundant, vividly colored predator: the sunflower sea star.

This large starfish – capable of stretching over 3 feet wide – cruises the ocean floor in hues of orange, yellow, or purple, gliding swiftly on thousands of tube feet. Its multiple arms, which can number up to 24, allow for remarkable mobility.

Restoring sunflower sea stars

When a mysterious disease almost wiped out sunflower sea stars in 2013, a domino effect ensued. A large number of purple sea urchins devoured nearly all of Northern California’s iconic kelp forests. 

Now, however, scientists are hopeful that the sunflower sea star might soon reclaim its place in the region’s marine environment. 

Several pioneering labs, including ones in the Bay Area and Monterey County, are successfully growing these starfish with the goal of bolstering the species and restoring balance to local ecosystems.

Sunflower sea stars raised in tubs

At the California Academy of Sciences in San Francisco, behind a closed exhibit and through a locked door, biologist Riah Evin has been overseeing 137 sunflower sea stars raised in saltwater jars and tubs. In these containers, the starfish are fed bits of herring to sustain their growth.

These juvenile stars are among the remnants of 11 million embryos that Evin began working with in February. “These are the survivors,” said Evin. “That’s way better than I had hoped for.”

Eventually, many of them will be displayed at the Academy of Sciences, giving the public a rare glimpse of a starfish that has all but disappeared from California’s coastal waters.

Scientific value and conservation goals

More importantly, these sunflower stars are crucial to research. By raising them from infancy, Evin and other scientists are contributing to an international conservation effort to better understand the species and protect it from future crises. 

Named critically endangered in 2020, sunflower sea stars were the subject of a conservation roadmap in 2022 that called on labs to breed and study them.

If scientists manage to decode the genetics behind their resistance (or susceptibility) to the disease that nearly eradicated them, they may eventually release healthy individuals back into the Pacific Ocean. 

The hope is that reintroduced sunflower sea stars could help control the region’s exploding purple urchin populations, paving the way for devastated 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 sea stars. “I’m very hopeful.”

A species on the brink of extinction

The statistics are sobering: since 2013, an estimated six billion sunflower sea stars have died from Baja California to Alaska because of an ailment known as sea star wasting disease. 

With this critical predator absent, purple sea urchins have proliferated, ravaging entire undersea forests of bull kelp. Scientists say 96% of Northern California’s kelp forests have disappeared over that period.

Kelp forests are essential habitats for numerous marine creatures – from fish and abalone to sea otters. Otters, found south of the Bay, play a protective role by feeding on urchins, but their range does not extend far enough to rescue Northern California’s compromised kelp.

Reintroducing natural predators

While volunteers have tried “seeding” kelp and removing urchins by hand in select coves, experts believe that reintroducing natural predators like sunflower sea stars (and possibly sea otters) would be more sustainable and far-reaching. 

Sunflower sea stars are exceptionally effective hunters, moving quickly across the seabed to overtake urchins before extending their stomachs to digest the prey externally. Afterward, only a clean shell remains.

Maximizing survival and preventing cannabilism

Yet researchers like Evin remain unsure of exactly how to keep these starfish flourishing. Scientists still do not fully understand the disease that decimated them, despite working on the puzzle for over a decade. In labs across the state, only six adult sunflower stars exist, and breeding techniques remain experimental.

“There’s a little bit of a ‘Thunderdome’ going on,” Evin joked while describing the fiercely competitive environment in which younger stars can devour each other if food is scarce. One particularly aggressive individual managed to consume hundreds of its siblings.

Evin is also investigating what diet optimally sustains these stars, testing everything from urchins to prawns. This feeding research aims to maximize survival, preventing the cannibalism that can occur if the starfish lack adequate nutrition.

Challenges with sunflower sea star larvae

Back in February, Evin traveled to Birch Aquarium in San Diego, where she helped spawn an adult male and female sunflower sea star using a hormone injection. The pair produced billions of eggs and sperm, which fused into embryos. 

Those offspring, divvied up among institutions like the Academy of Sciences and Moss Landing Marine Laboratories, are the foundation for current breeding trials.

Maintaining healthy conditions for tiny sea star larvae proved challenging – until Evin discovered they thrived in jars of saltwater spun by automated stirrers purchased from kitchen supply stores.

The larvae eventually sprouted five arms, but many soon turned on each other, forcing Evin to fine-tune her feeding strategies.

Understanding the mysterious wasting disease

Scientists are also eager to analyze the starfish’s DNA to gain insights into the genetics behind the wasting disease.

Before any reintroduction to the wild can happen, they must ensure they are not inadvertently reintroducing the pathogen into marine environments. Regulatory agencies want a clearer picture of the disease’s causes and transmission pathways.

“What we don’t want to do is reintroduce (the disease) to recovered sea star populations,” said Ian Kelmartin, an environmental scientist with the California Department of Fish and Wildlife. “To get a handle on that, we need to understand what the disease is.”

A glimpse of hope in the lab

Until more is known, the starfish remain confined to facilities like Evin’s. Ashley Kidd, a project manager with the Sunflower Star Lab in Moss Landing, sees these labs as living arks – safe havens for a species on the brink. 

“Zoos and aquariums are living arks,” she said. “It is tragic in a way, but very useful if you can use it in time.”

By nurturing sunflower sea stars in captivity, researchers aim to one day restore a key predator to the Pacific Ocean, where it can help rein in purple urchins and nurture the revival of kelp forests. 

Whether that vision comes to fruition depends on cracking the mystery of sea star wasting disease and ensuring enough of these starfish can survive – and thrive – back in their underwater realm.

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