Scientists say they have solved the mystery of what killed more than 5 billion sea stars
Sea stars – often known as starfish – typically have five arms and some species sport up to 24 arms. They range in color from solid orange to tapestries of orange, purple, brown and green.
Starting in 2013, a mysterious sea star wasting disease sparked a mass die-off from Mexico to Alaska. The epidemic has devastated more than 20 species and continues today. Worst hit was a species called the sunflower sea star, which lost around 90% of its population in the outbreak's first five years.
'It's really quite gruesome,' said marine disease ecologist Alyssa Gehman at the Hakai Institute in British Columbia, Canada, who helped pinpoint the cause.
Healthy sea stars have 'puffy arms sticking straight out,' she said. But the wasting disease causes them to grow lesions and 'then their arms actually fall off.'
The culprit? Bacteria that has also infected shellfish, according to a study published Monday in the journal Nature Ecology and Evolution.
The findings 'solve a long-standing question about a very serious disease in the ocean,' said Rebecca Vega Thurber, a marine microbiologist at University of California, Santa Barbara, who was not involved in the study.
It took more than a decade for researchers to identify the cause of the disease, with many false leads and twists and turns along the way.
Early research hinted the cause might be a virus, but it turned out the densovirus that scientists initially focused on was actually a normal resident inside healthy sea stars and not associated with disease, said Melanie Prentice of the Hakai Institute, co-author of the new study.
Other efforts missed the real killer because researchers studied tissue samples of dead sea stars that no longer contained the bodily fluid that surrounds the organs.
But the latest study includes detailed analysis of this fluid, called coelomic fluid, where the bacteria Vibrio pectenicida were found.
'It's incredibly difficult to trace the source of so many environmental diseases, especially underwater,' said microbiologist Blake Ushijima of the University of North Carolina, Wilmington, who was not involved in the research. He said the detective work by this team was 'really smart and significant.'
Now that scientists know the cause, they have a better shot at intervening to help sea stars.
Prentice said that scientists could potentially now test which of the remaining sea stars are still healthy — and consider whether to relocate them, or breed them in captivity to later transplant them to areas that have lost almost all their sunflower sea stars.
Scientists may also test if some populations have natural immunity, and if treatments like probiotics may help boost immunity to the disease.
Such recovery work is not only important for sea stars, but for entire Pacific ecosystems because healthy starfish gobble up excess sea urchins, researchers say.
Sunflower sea stars 'look sort of innocent when you see them, but they eat almost everything that lives on the bottom of the ocean,' said Gehman. 'They're voracious eaters.'
With many fewer sea stars, the sea urchins that they usually munch on exploded in population – and in turn gobbled up around 95% of the kelp forest s in Northern California within a decade. These kelp forests provide food and habitat for a wide variety of animals including fish, sea otters and seals.
Researchers hope the new findings will allow them to restore sea star populations — and regrow the kelp forests that Thurber compares to 'the rainforests of the ocean.'
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Newsweek
an hour ago
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Death of 5 Billion Starfish Baffled Scientists—Until Now
Based on facts, either observed and verified firsthand by the reporter, or reported and verified from knowledgeable sources. Newsweek AI is in beta. Translations may contain inaccuracies—please refer to the original content. Researchers have traced the devastating loss of more than 5 billion sea stars—known colloquially as starfish—along the Pacific coast of North America over the past decade to a bacterial culprit. The findings, published in Nature Ecology and Evolution, help explain an ecological crisis that saw sunflower sea star populations plunge by up to 90 percent from Alaska to Mexico since 2013, reshaping vital marine ecosystems in the U.S. and Canada. Why It Matters The mass die-off, driven by "sea star wasting disease," has had devastating ripple effects across Pacific coastal ecosystems, including those off the U.S. These predators, especially the sunflower sea star, help regulate sea urchin populations. Their disappearance led to unchecked sea urchin growth, which in turn destroyed extensive kelp forests—habitats called the "rainforests of the ocean" due to their biodiversity and importance for marine mammals, fish, and invertebrates. In Northern California alone, kelp coverage dropped by 95 percent within a decade as a result. FILE - Starfish on the coast of Acadia National Park. FILE - Starfish on the coast of Acadia National Park. Edwin Remsberg/VWPics via AP Images What To Know In 2013, sea stars from Alaska to Mexico started exhibiting symptoms of "wasting syndrome"—including twisted limbs, lesions, and disintegration—that gradually devastated more than 20 species, with the sunflower sea star most affected. "It's really quite gruesome," said marine disease ecologist Alyssa Gehman from the Hakai Institute in British Columbia, Canada. The disease was so severe it often caused the sea stars' arms to detach entirely, added Gehman, who helped pinpoint its cause. Scientists had previously suspected a virus, but years of research showed that the densovirus found in dying sea stars was not the cause. Focus shifted after researchers analyzed the sea stars' coelomic fluid—their internal body fluid—and identified Vibrio pectenicida, a bacteria also known to infect shellfish, as the real culprit. In the lab, fluid from sick sea stars was injected into healthy counterparts, causing the wasting symptoms to recur. When the team heat-treated this fluid, killing the microbes, healthy sea stars did not develop disease—definitively pointing to a microbial origin. The bacteria was isolated and pure cultures were shown to cause the illness. The findings, achieved after more than a decade of setbacks, open the door for targeted conservation strategies. Marine microbiologist Rebecca Vega Thurber of UC Santa Barbara, who was not involved in the study, called it the solution to a "long-standing question about a very serious disease in the ocean." What People Are Saying Blake Ushijima, a microbiologist at University of North Carolina, Wilmington, praised the team's detective work, saying: "It's incredibly difficult to trace the source of so many environmental diseases, especially underwater." Drew Harvell, a researcher at Cornell University and University of Washington and study co-author, told The Washington Post: "It's personally incredibly fulfilling to me to have such a solid answer after all this time." Jason Hodin, a senior research scientist at the University of Washington and study co-author, said: "The lack of understanding what the disease is has really been a pretty major impediment to being able to move forward with all the kinds of restoration strategies that we'd like to be able to do." What Happens Next Scientists still aim to clarify how the bacterium spreads in the wild, whether it is native or introduced, and what influences—such as warming ocean temperatures—might fuel future outbreaks. This article contains reporting by The Associated Press
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3 hours ago
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Scientists find culprit after billions of sea stars killed off Pacific Coast: ‘It's really quite gruesome'
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