What Killed Over 5 Billion Sea Stars? Scientists Finally Solve Decade-Old Ocean Mystery

After more than a decade of search, scientists say they’ve finally found out the cause of a devastating sea star die-off that wiped out more than five billion sea stars along the Pacific coast of North America, blaming the mass killing on a bacterium called Vibrio pectenicida, according to a report published by The Associated Press on Monday.

The mass die-off, which began in 2013, continues to impact over 20 sea star species across regions from Mexico to Alaska. Among the hardest hit was the sunflower sea star, which lost around 90% of its population in the outbreak’s first five years, the report said.

“It’s really quite gruesome,” marine disease ecologist Alyssa Gehman of the Hakai Institute in British Columbia told the US-based news agency, explaining, “Healthy sea stars have puffy arms sticking straight out. But the wasting disease causes them to grow lesions and then their arms actually fall off.”

Not a Virus After All

For years, scientists were stumped as early studies had suggested that a virus was behind the mysterious illness.

Melanie Prentice of the Hakai Institute, a co-author of the new study published in Nature Ecology and Evolution, explained that the previously suspected densovirus is actually a normal part of healthy sea star biology.

The key breakthrough, the report said, came when researchers began analysing coelomic fluid — the internal fluid that surrounds a sea star’s organs. That is where they found the deadly bacteria.

‘Really Smart and Significant’ Work

“It’s incredibly difficult to trace the source of so many environmental diseases, especially underwater,” microbiologist Blake Ushijima of the University of North Carolina, Wilmington, who was not involved in the study, told AP as he praised the research as “really smart and significant.”

Hopes for Recovery and Ecosystem Balance

Scientists are now hopeful about saving what’s left. Prentice said researchers can now test sea stars for infection, breed healthy ones in captivity, and possibly reintroduce them into areas where they have vanished.

The findings hold significance not just for the sea stars, but for the entire marine ecosystem. Sunflower sea stars are top predators that help control sea urchin populations. Without them, urchins exploded in number, devouring 95% of Northern California’s kelp forests, the habitat that is crucial for survival of otters, fish and seals, per AP.

“Sunflower sea stars look sort of innocent when you see them, but they eat almost everything that lives on the bottom of the ocean,” Gehman told the publication suggesting that they are0 “voracious eaters”.