Sea Star Killing Bacteria is Finally Revealed

On Monday, August 4, scientists finally discovered the bacteria that had been the cause of a 12-year sea star pandemic. This disease caused five billion sea stars along the Pacific Coast of North America to disintegrate into goo.

The sunflower sea star population was affected the most, with 90 percent of it disappearing within the first five years. As a result, the prey of these sea stars, sea urchins, exploded in numbers and obliterated whole kelp forests.

A team of scientists led by Alyssa-Lois Gehman, a marine ecologist from the Hakai Institute in British Columbia, performed studies and finally discovered the cause of the deadly disease after four grueling years of research. It was a bacterium called Vibrio pectenicida, which has the ability to dissolve tissue. This breakthrough paved the path for rehabilitation programs that would not have been possible before.

According to sea star experts, “knowing the cause should make it easier to refine and expand such efforts.” Many restoration projects have been undertaken to revive the 20+ sea star species that have diminished greatly in number. For example, a program led by the Nature Conservancy seeks to restore sunflower sea stars to their natural habitat. Meanwhile, more than a dozen aquariums are working together to breed these animals in captivity.

In order to determine what had caused this sea star pandemic, Dr. Gehman and her team of scientists conducted experiments where they took contaminated sea stars from the ocean and isolated them. Then, they collected specimens of coelomic fluid, the sea stars’ version of blood, and injected them into healthy stars.

At the same time, the scientists heated up some of the fluid samples, which killed any bacteria or viruses that might be the culprit. These “purified” samples were then inserted into healthier stars. After several days, the team observed that the sea stars that were injected with “purified” fluid remained in good shape, while nearly all of the stars injected with diseased fluid died.

By genetically comparing the two different coelomic fluid samples, the researchers came across a single species of bacteria that existed in the untreated samples. The microbe, Vibrio pectenicida, was then isolated and grown in cultures, where the team continued to perform tests on it to confirm it was indeed the cause of sea stars dying.

“To have one pathogen, V. pec, stand out so clearly as causing the disease was surprising and exciting,” said Dr. Gehman.

Sources:

https://www.nytimes.com/2025/08/04/science/sea-stars-disease-vibrio-pectenicida.html

https://phys.org/news/2025-08-scientists-mystery-billion-sea-stars.html