What’s Happening to the Starfish?

Written by: Keya Gambhir

Imagine a starfish twisting its arms into strange spirals, developing white lesions, shedding limbs that writhe independently, and then dissolving into a puddle of goo. This horrifying scene has played out billions of times along the Pacific Coast for over a decade. Finally, scientists say they’ve pinpointed what’s behind it all.

A Crisis That Began in 2013

Since 2013, sea stars from Alaska to Baja California have been devastated by a disease known as sea star wasting syndrome (SSWD). The epidemic has struck more than 20 species, including the giant sunflower sea star, which has lost an estimated 90% or more of its population, more than 5 billion individuals, making it critically endangered.

Symptoms begin with twisted arms, white spots, and deflated bodies, followed by limb detachment and complete tissue disintegration, sometimes within days or weeks.

The Long Hunt for a Culprit

Early investigations locked onto a virus, densovirus (SSaDV), as the cause. That theory later collapsed when follow-up studies couldn’t replicate the results, revealing the virus as a normal resident in healthy sea stars. Scientists then considered environmental triggers like toxic algae, oxygen loss, or high temperatures. But these explanations failed to account for the rapid, widespread transmission across multiple species and distant Pacific locations.

Breakthrough in 2025: A Bacterium Revealed

A new study published on August 4, 2025, in Nature Ecology & Evolution finally provides answers. The researchers from the Hakai Institute, University of British Columbia, and University of Washington isolated a strain called Vibrio pectenicida FHCF‑3 from the coelomic fluid (sea star “blood”) of sick sunflower stars. After four years of rigorous experiments, they satisfied Koch’s postulates: healthy sea stars exposed to untreated fluid or cultured Vibrio pectenicida developed wasting disease and died, while controls remained alive. That definitive link marked the likely cause of the mass die-offs.

Why Some Scientists Offer Caution

Despite the breakthrough, some researchers remain cautious. Marine biologist Ian Hewson notes the study tested only one species. Other sea stars may succumb to different pathogens, or environmental stressors may play a larger role in some cases. Injecting bacteria under lab conditions may not mirror natural transmission. Still, the majority of experts view the discovery as the most compelling explanation yet and a crucial foundation for rescue efforts.

From Goo to Rescue: Next Steps in Conservation

Knowing the pathogen unlocks a range of conservation possibilities. Scientists can now screen sea star populations for infection and identify naturally resistant individuals. Some labs are trialing breeding disease-resistant sunflower sea stars for reintroduction. Researchers are exploring treatments like probiotics or bacteriophages to reduce or prevent infection. Caution is required, as relocated sea stars must not spread the bacteria to new areas.

The Ecological Fallout from Losing Sea Stars

Sunflower sea stars aren’t just eye-catching. They’re keystone predators, feasting on sea urchins, clams, and smaller creatures. When they disappeared, sea urchin populations exploded, consuming over 95% of kelp forests in Northern California. The loss of kelp devastates marine habitats, fisheries, and even coastal resilience. Millions of dollars in recreational abalone fisheries were lost, purple urchin barrens replaced lush kelp beds, and many fish species, sea otters, and other wildlife vanished along with their habitat.

The Climate Connection

Warmer ocean temperatures, such as those during the 2013–2016 “Blob” heatwave, may have fueled outbreaks. Vibrio bacteria are known to multiply faster in warmer waters, making them sensitive to climate change. Sea stars in colder regions appear to fall ill more slowly and less frequently. As oceans warm, similar outbreaks may become more frequent unless mitigated.

A Glimmer of Hope

Though the loss is historic, so is this discovery. As marine ecologist Alyssa Gehman says, “We knew we were working in a system where the answer was not correct the first time... We spent a lot of time confirming everything.” With a known bacterial culprit, researchers are now building targeted strategies to monitor, treat, breed, and restore sea star populations and, in turn, rebuild the kelp forests and marine ecosystems they support. Restoring balance may take time, but after 12 years of mystery and loss, scientists now know who the killer is and how we might fight back.