Starfish Have Been Dying in Record Numbers—Now Scientists Think They Know Why
Species along the West Coast, from Mexico to Canada, have been dying by the millions since 2013.
In June 2013, a scientist in Washington State observed disturbing things happening to the usually-healthy starfish population at Starfish Point in Olympic National Park. The brightly-colored bodies of sea stars were covered in white lesions, some stars were missing their arms, and others appeared to be disintegrating.
That fall, sea star die-offs were reported all along the West Coast, from Orange County, CA to Anchorage. And in 2014, there were more.
Called ‘sea star wasting,’ the disease is not new, but scientists say the outbreak that began in the summer of 2013 is the largest disease epidemic ever observed in wild marine animals. Die offs from the disease have ebbed and flowed since then and have affected more than 20 species. The sunflower sea star, a large species with arms that can span four feet across, has been particularly hard hit.
Now, according to research published in the journal Science Advances, researchers are linking the unprecedented demise of sea stars with warmer waters due to climate change.
“The heat wave in the oceans — a product of increasing atmospheric temperatures — is exacerbating the sea star wasting disease,” study co-author Drew Harvell, a professor of ecology and evolutionary biology at Cornell University said. “It’s a lethal disease, and when you add a higher temperature to that, it kills faster, causing a bigger impact.”
In the study, researchers at Cornell and the University of California, Davis, focused on the sunflower sea star. Data gathered from deep-water trawlers and shallow-water divers revealed sea star declines of 80 – 100 percent across a 3,000-kilometer range. The timing of the declines in nearshore waters coincided with higher sea surface temperatures.
The lack of sea stars in deeper waters was especially notable.
“Many people expected the sunflower stars to be taking refuge in the deep water where we couldn’t count them,” Steve Lonhart, a researcher with the NOAA, told Science. “We hoped they were hiding down there — this research shows that hope was naïve."
The impact on sea stars themselves isn’t the end of the story. Sunflower stars are a major predator of sea urchins, and sea urchins feast on kelp.
“In California, Washington, and parts of British Columbia, sunflower sea stars keep urchins under control,” Joe Gaydos, the science director at the University of California, Davis' SeaDoc Society, said, according to NPR. “Without sunflower stars, urchin populations expand and threaten kelp forests and biodiversity. This cascading effect has a really big impact."
"If you looked on land, it would almost be akin to clear-cutting a forest," he said.
Will sea stars bounce back? 2018 research suggests that some stars might be able to survive — and even change their genetic makeup as a result of the disease.
According to the New York Times, the sunflower star has not yet returned to the lower 48 states, but last summer, they reappeared on the south coast of Alaska.
“We don’t know where exactly they came from,” Brenda Konar, a professor of marine biology at the University of Alaska, Fairbanks, told the Times. “They were pretty small and we don’t know if they’re going to survive. So we’re really curious about what we’ll see next summer.”
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