Scientists deploy a 24-armed secret weapon to save California's kelp forests

Off the coast of Monterey, California, a dedicated team of researchers readies itself for its inaugural dive into the chilly and turbulent waters of the Pacific Ocean.

On the vessel's back deck, Ashley Kidd, co-founder of the non-profit Sunflower Star Laboratory, provides the divers with their final instructions: "Dive No 1 … stars in the water."

As the divers enter the water, they carry with them plastic bags containing the true stars of this endeavor. Upon reaching the ocean floor, they carefully place these creatures inside specialized cages, leaving the doors wide open to encourage these extraordinary predators to explore the seabed, where they once played a vital role in the marine ecosystem.

"We have a star that decided to go for a walk today," Kidd noted while observing one particularly active specimen.

Kidd's team aims to restore the sunflower sea star, a critically endangered marine invertebrate that resembles something out of a science fiction narrative rather than a typical starfish.

"They are a sea star, but the fascinating aspect of these animals is that they can have more than five arms," Kidd explained. "They can have as many as 24 arms, and our goal is to reintroduce them to the ecosystem."

A marine apocalypse in the Pacific

The majestic underwater landscape that once thrived with towering kelp forests has undergone severe changes. Often referred to as the redwoods of the sea, kelp can grow taller than a ten-story building at an impressive rate of up to two feet per day. These lush underwater canopies not only provide crucial habitat for thousands of marine species but also play a significant role in the ocean's ecological processes, which produce approximately half of the Earth's oxygen.

Additionally, kelp forests serve as essential buffers against global climate change. Globally, these ecosystems sequester around 200 million tons of carbon dioxide annually, effectively pulling significant volumes of greenhouse gas from the atmosphere to fuel their growth.

However, over the past decade, these indispensable underwater sanctuaries have faced devastation along the Pacific coast.

Since around 2013, a marine heatwave, exacerbated by climate change, has elevated water temperatures along the West Coast. This rise in temperature facilitated the spread of sea star wasting syndrome, a condition that resulted in the disintegration of sunflower sea stars and led to more than a 90% decline in their Pacific population.

"There were 6 billion sunflower stars from Alaska to Baja California," stated Reuven Bank, co-founder of the Sunflower Star Laboratory. "Six billion with a B."

The extinction of these stars triggered a collapse of the delicate ecological balance that had existed for generations.

"95% of our kelp forests have disappeared in the last 10 to 12 years," Bank noted.

The 'halo of fear'

Sunflower sea stars primarily feed on purple sea urchins. In the absence of these stars, the urchin population proliferated uncontrollably. Large swathes of these spiny grazers covered the ocean floor, voraciously consuming the roots and stalks of kelp until extensive underwater forests were transformed into barren wastelands.

To reverse this environmental damage, researchers are striving to restore what they describe as the "halo of fear."

"When urchins and other grazers detect a sunflower star approaching, they flee in terror," Bank explained. "They subsequently hide more and reduce their feeding, retreating up to 16 feet in every direction. They consume urchins and instill fear in them."

In the lab, Bank exhibited the remarkable feeding capabilities of a healthy star.

"So this remarkable alien creature is Titan," Bank shared, placing a purple urchin directly onto the expansive arm of a sea star resembling a large dinner plate. "That urchin's fate is sealed. He's being funneled directly to the star's mouth."

Employing hundreds of tiny tube feet that function like a hydraulic system, a single sunflower star can consume three to four urchins in a day. Their deterrent effect is even more pronounced since the mere scent of a star prompts urchins to seek refuge, allowing juvenile kelp the opportunity to establish and flourish.

Rebuilding an ecosystem from scratch

Within the lab's breeding facility, researchers are employing advanced marine husbandry techniques to cultivate a new generation of sea stars in temperature-controlled tanks. This work is essential, as the wild population along the Pacific coast has dwindled to alarming levels.

"The known number of sunflower stars in Monterey Bay is zero," Bank revealed.

Their field experiments represent a pioneering effort for California. By temporarily releasing lab-raised stars onto the ocean floor, researchers can monitor their movement and observe local urchins' behavioral reactions, gathering the baseline data necessary for large-scale reintroduction into the wild.

If these trials prove successful, the team aims to establish a permanent population of sunflower stars in Monterey Bay within the next few years, triggering a cascading effect that could ultimately restore a severely impacted coastline.

"Restoring the sunflower star," Bank concluded, "is the single most important step you can take to save our beleaguered kelp forests here in California."

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