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Metro
6 days ago
- Health
- Metro
Scientists have solved ‘one of the greatest ocean mysteries'
Hiyah Zaidi Published August 13, 2025 11:47am Link is copied Comments Starfish were melting in the ocean and no one had any idea why. This was back in 2013, and the epidemic swept across the Pacific Coast of North America, swiftly turning starfish - or sea stars - into goo. But now, researchers know why this is happening and have finally solved what they dub as one of the greatest mysteries in the ocean. So, what's going on? (Picture: Hakai Institute) It's down to sea star wasting disease (SSWD), which results in distorted sea star bodies and fragmented arms as it melts away tissue in a matter of days. More than 10 years later, SSWD has been described as the largest epidemic ever recorded in a wild marine species and, what researchers say, is one of the 10 greatest unsolved ocean mysteries. But now they have identified the pathogen responsible (Picture: Hakai Institute) After a five-year research project looking into the cause of SSWD, a study led by Dr Melanie Prentice and Dr Alyssa Gehman, of the Hakai Institute in British Columbia, Canada, and other institutions revealed that a microscopic bacterial relative of cholera, specifically Vibrio pectenicida, is the culprit of the sea star mass deaths. So how did the researchers figure this out? (Picture: Bennett Whitnell/Hakai Institute via AP) Looking through their sea star samples, the researchersfound high concentrations of V. pectenicida – but only in the sick ones. They then exposed healthy sea stars to the bacteria and the poor little stars melted away within days. Knowing what was causing these stars to melt was impossible without a known pathogen, as sea stars can respond to other stressors and diseases with similar visual signals of contortion and loss of arms (Picture: Grant Callegari/Hakai Institute via AP) Keeping these sea stars alive is vital, and their extinction could play havoc for the marine ecosystem. Dr Prentice said: 'When we lose billions of sea stars, that really shifts the ecological dynamics. In the absence of sunflower stars, [kelp-eating] sea urchin populations increase, which means the loss of kelp forests, and that has broad implications for all the other marine species and humans that rely on them' (Picture: Grant Callegari/Hakai Institute via AP) This virus harmed a lot of sea stars. Over 90% of sunflower sea stars (Pycnopodia helianthoides, like the one pictured), which can grow 24 arms and become the size of a bicycle tire, were wiped out by the disease in the past decade. This resulted in them being added to the International Union for Conservation of Nature's Red List of critically endangered species. But the loss of kelp forests is also hazardous as they provide habitat for thousands of marine creatures and contribute millions to local economies through fisheries, recreation, and tourism (Picture: Getty) Now that researchers have identified the pathogen that causes SSWD, the next step is to look at the drivers of the disease. One path the researchers will look at is the rising ocean temperatures, since the disease and other species of Vibrio are known to proliferate in warm water. And with any luck, the discovery will help guide management and recovery efforts for sea stars and the ecosystems affected by their decline (Picture: Getty)
1News
05-08-2025
- Health
- 1News
Scientists say they have solved the mystery of what killed more than 5 billion starfish
Scientists say they have at last solved the mystery of what killed more than 5 billion sea stars off the Pacific coast of North America in a decade-long epidemic. Sea stars – often known as starfish – typically have five arms and some species sport up to 24 arms. They range in colour 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'. ADVERTISEMENT A sunflower sea star is reduced to goo by sea star wasting disease at Calvert Island, British Columbia, Canada, in 2015. (Source: Grant Callegari/Hakai Institute via AP) The culprit? Bacteria that has also infected shellfish, according to a study published today 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. ADVERTISEMENT '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'. Healthy populations of sunflower sea stars are found in the Knight Inlet fjord of the Central Coast of British Columbia, Canada, in 2023. (Grant Callegari) 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. With a lack of predatory sunflower sea stars, sea urchins proliferate in Hakai Pass, British Columbia, Canada, in 2019. (Source: Grant Callegari/Hakai Institute via AP) ADVERTISEMENT 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'.
