Scientists have solved ‘one of the greatest ocean mysteries'

Metro

4 days ago

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)