For a decade, sea stars vanished by the millions. A pivotal discovery reveals why.

A detailed exploration into the mission to uncover the hidden danger to sea stars.

Recalling the scene, Drew Harvell says, “It resembled a war zone. It was almost impossible to comprehend.”

She reflects on a day in December 2013, along the Washington state shoreline, confronting hundreds of deteriorating sea stars at low tide. “Entire limbs appeared to have separated from their bodies, as if a disaster had struck,” she recounts.

These sea creatures were afflicted by sea star wasting syndrome, a condition that seems straight out of a nightmare: the stars develop body sores, detach their arms, which might then creep away, until the stars completely break apart.

The Enigma Begins

In 2013, the pressing question was: What exactly led to the demise of these stars? Marine experts like Harvell could pinpoint the indicators of this wasting disease but were puzzled by its root cause. Determined to resolve the mystery, they gathered affected stars to ascertain any pathogenic culprit. Thus commenced their intensive investigation.

“Our initial knowledge of sea star biology was limited,” admits Alyssa Gehman, another marine disease specialist. Unlike human pathogens, where vast data exist, sea stars are not as well-documented. This knowledge gap proved challenging in identifying the disease.

A delay in symptom onset also complicated matters. Some stars harbored the disease but showed no immediate symptoms, blurring the line between healthy and sick stars in early tests.

Although a virus came under scrutiny as early as 2014, it was only another virus among many present, but not the decisive agent causing the devastation.

“The findings were perpetually perplexing,” recalls Harvell.

Realizing the Stars' Ecosystem Role

Over the decade since the onset, new hypotheses emerged, but none led to clear answers. It gradually became evident that understanding was crucial—not only for research but because the sunflower sea stars’ ecological impact was immense.

“Their absence taught us much,” notes Gehman. Before the outbreak, the prowess of sunflower stars as dominant predators was recognized, capable of instigating panic-fueled escapes among their prey.

These predation dynamics maintained ecological balance. With their decline, unchecked sea urchin populations surged, contributing to the deterioration of Northern California's kelp forests, vital to numerous marine species.

To restore ecological balance, organizations collaborated to breed these stars in captivity, hoping to reintroduce them. But the cause of the wasting disease had to be identified to ensure these efforts weren’t in vain.

The Search Intensifies

In 2021, Harvell and Gehman, galvanized by concerted efforts, embarked on a project to finally demystify the wasting disease. With dedication from Dr. Melanie Prentice and others, they honed in on experiments necessary for progress.

“Ethically challenging,” Gehman reflects, because it necessitated infecting stars deliberately. Yet, the greater purpose for species survival justified their approach.

Unveiling the Culprit

Their efforts bore fruit: They identified a bacterium in the stars’ coelomic fluid – essentially the sea star’s bloodstream. By isolating this bacterium and re-infecting with it, they noted its fatal impact, confirming it as the disease's cause.

“It was an exhilarating discovery,” Harvell recalls. Despite initial skepticism of finding a common bacterium, isolating and confirming it brought immense relief.

Amy Chan, from the University of British Columbia, helped culture this bacterium, further establishing its presence as the prime suspect. Tests affirmed its lethal role.

“Joy and relief swept over us,” Harvell recalls, a triumphant moment confirming years of relentless inquiry.

Preparing for a New Beginning

With this breakthrough, a roadmap for conservation becomes feasible. It opens avenues for testing environments for the bacterium, understanding susceptibility conditions, and crafting strategies to disseminate healthy stars back to their native habitats.

“Armed with this knowledge, we are one step closer to rehabilitating sea star populations,” enthuses Harvell. Solving this mystery empowers scientists and conservationists alike to act decisively for recovery.