Scientists say they have solved the mystery of what killed more than 5 billion starfish
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'.
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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.
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'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)
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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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1News
6 days ago
- 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'.
NZ Herald
7 days ago
- NZ Herald
Sea star wasting disease has killed billions of starfish and destroyed kelp ecosystems
Since the start of the outbreak in 2013, scientists have struggled to pinpoint the cause. However, a group of researchers said today that they had finally identified a culprit: a bacterial cousin of the pathogen behind cholera. 'I've wondered and thought about this, and felt haunted by the fact that we did not know what the agent was,' said Drew Harvell, a researcher at Cornell and the University of Washington who co-wrote a paper in the journal Nature Ecology and Evolution on the discovery. 'So it's personally incredibly fulfilling to me to have such a solid answer after all this time,' she said. Knowing the cause of the wasting syndrome is key to conservation efforts, including plans to breed a galaxy of disease-resistant starfish and restore the ecosystems in which they live. Fewer starfish has led to a surge in sea urchins upon which they prey. The urchins, in turn, have mowed through stands of kelp that are needed to help sequester carbon and guard against coastal erosion. '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,' said Jason Hodin, a senior research scientist who breeds starfish at the University of Washington who also co-authored the paper. Yet not every starfish scientist is convinced the strain of Vibrio pectenicida bacteria identified in the study is really behind the die-off, considered the largest recorded marine epidemic in the wild. Researchers have got it wrong before: incorrectly attributing the wasting disease to a virus. 'It's absolutely critical not to jump the gun,' Cornell marine biologist Ian Hewson said. For the most recent study, the researchers focused on the sunflower sea star, a voracious predator as wide as a hula hoop that corrals and consumes clams and sea urchins with up to two dozen limbs. Since 2013, more than five billion have died of the wasting disease. By 2023, the situation was so bad that federal officials proposed protecting it under the Endangered Species Act. Hakai Institute research scientist Alyssa-Lois Gehman checks on an adult sunflower sea star in the US Geological Survey's Marrowstone Marine Field Station in Washington state. Photo / Kristina Blanchflower, Hakai Institute In the research experiments, which lasted for four years, healthy starfish died after being exposed to untreated fluids extracted from sick stars, while those exposed to fluids that were heated were fine, suggesting a microbe is behind the disease. A genetic analysis of the deceased starfish revealed the first hints that a strain of Vibrio was responsible. The microbe is in the same genus as the bacteria that cause cholera, as well as certain foodborne illnesses. The researchers found the same genetic markers of the pathogen in wild sunflower sea stars wasting away off the coast of British Columbia in Canada, and Alaska. The most convincing piece of evidence came after the researchers isolated and grew a pure culture of the Vibrio bacteria. The vast majority of sunflower sea stars exposed to that strain in the lab melted away while healthy controls lived on. Melanie Prentice, an evolutionary ecologist at the Hakai Institute and the University of British Columbia who led the work, said her team spent years trying to poke holes in their theory that the bacteria was causing the wasting. 'Eventually, we had to be like, 'Okay, maybe we're right here.' But it was a long process.' Hewson, who was not involved in the study, cautioned against overinterpreting the results. He noted that the team experimented on one type of starfish, meaning other species hit with wasting may have fallen victim to a different pathogen or changes in the environment. Injecting starfish with bacteria, which the team did in some of its experiments, may induce a response not seen in the wild. And the gruesome process of dissolving into goo, he added, may be a stress response to many different factors. He said: 'It's really, really hard to do these type of experiments, and particularly the interpretation of it is somewhat difficult'. In 2014, a team of researchers that included Hewson and Harvell published a paper identifying a kind of virus called a densovirus as the cause of the mass starfish mortality. In subsequent experiments, some of those same researchers were unable to replicate the results. This time, Alyssa-Lois Gehman, a marine disease ecologist also at the Hakai Institute and University of British Columbia and a study co-author, is confident they got it right because the team was able to grow colonies of the Vibrio bacteria outside of the sea stars and use them to reinfect healthy starfish. In the past, the researchers weren't able to grow a pure culture of the densovirus in the lab and complete that last step. In some of its experiments, the team showed that the disease can spread not just through injections but also when starfish simply share the same water. Amy Chan, a marine microbiologist at the Aquatic Microbiology and Virology Lab at the University of British Columbia, compares bacteria cultures from a sick versus a healthy sea star. Photo / Toby Hall, Hakai Institute 'We knew we were working in a system where the answer was not correct the first time, and so we were very careful,' Gehman said. 'We spent a lot of time confirming everything that we did. Every experiment was rerun. We didn't rely on one trial to give us answers.' Now, scientists want to find potential reservoirs of the bacteria in the open ocean, test other species of starfish in the lab to see how they respond to the pathogen and see if warming waters fuel outbreaks. The ultimate goal is to breed sunflower sea stars that can tolerate the wasting disease and use them to repopulate the Pacific. 'This discovery is huge to the success of that programme,' Harvell said. 'It was just not going to be possible if we didn't know what was killing it.'
1News
11-07-2025
- 1News
US dinosaur museum makes a find deep under own parking lot
A Denver museum known for its dinosaur displays has made a fossil bone discovery closer to home than anyone ever expected - under its own parking lot. It came from a hole drilled more than 230 metres deep to study geothermal heating potential for the Denver Museum of Nature and Science. The museum is popular with dinosaur enthusiasts of all ages. Full-size dinosaur skeletons amaze kids barely knee-high to a parent, much less to a Tyrannosaurus. This latest find is not so visually impressive. Even so, the odds of finding the hockey-puck-shaped fossil sample were impressively small. With a bore only 5 centimetres wide, museum officials struggled to describe just how unlikely it was to hit a dinosaur, even in a region with a fair number of such fossils. ADVERTISEMENT 'Finding a dinosaur bone in a core is like hitting a hole in one from the moon. It's like winning the Willy Wonka factory. It's incredible, it's super rare,' said James Hagadorn, the museum's curator of geology. Core drilling used for geothermal feasibility and research to show what lies beneath the museum in the north parking lot at Denver Museum of Nature and Science. (Source: Denver Museum of Nature and Science via AP) Only two similar finds have been noted in bore hole samples anywhere in the world, not to mention on the grounds of a dinosaur museum, according to museum officials. A vertebra of a smallish, plant-eating dinosaur is believed to be the source. It lived in the late Cretaceous period around 67.5 million years ago. An asteroid impact brought the long era of dinosaurs to an end around 66 million years ago, according to scientists. Fossilised vegetation also was found in the bore hole near the bone. 'This animal was living in what was probably a swampy environment that would have been heavily vegetated at the time,' said Patrick O'Connor, curator of vertebrate paleontology at the Denver Museum of Nature and Science. Dinosaur discoveries in the area over the years include portions of Tyrannosaurus rex and triceratops-type fossils. This one is Denver's deepest and oldest yet, O'Connor said. ADVERTISEMENT Other experts in the field vouched for the find's legitimacy but with mixed reactions. 'It's a surprise, I guess. Scientifically it's not that exciting,' said Thomas Williamson, curator of paleontology at the New Mexico Museum of Natural History & Science in Albuquerque. Part of a fossilized vertebrae from a herbivorous dinosaur found deep under the parking lot of the Denver Museum of Nature & Science. (Source: Associated Press) There was no way to tell exactly what species of dinosaur it was, Williamson noted. The find is "absolutely legit and VERY COOL!' Erin LaCount, director of education programmes at the Dinosaur Ridge track site just west of Denver, said by email. The fossil's shape suggests it was a duck-billed dinosaur or thescelosaurus, a smaller but somewhat similar species, LaCount noted. The bore-hole fossil is now on display in the Denver Museum of Nature and Science, of course, but there are no plans to look for more under the parking lot. ADVERTISEMENT 'I would love to dig a 763-foot (233-metre) hole in the parking lot to excavate that dinosaur, the rest of it. But I don't think that's going to fly because we really need parking,' Hagadorn said.
