A sea star once "as common as a robin" off the Pacific coast of the U.S. is now considered an endangered species in the southern part of its range, and new research suggests climate change might be partly to blame.
Since 2013, a sea star wasting disease has devastated around 20 sea star species between Mexico and Alaska. While some species have begun to recover, the vitally important predatory sunflower star has not, a paper published Wednesday in Science Advances found. In fact, its population has decreased by 80 to 100 percent across a 3,0000 kilometer (approximately 1,864 miles) range between California and Canada.
The research team, led by Cornell University and University of California (UC), Davis, confirmed the decline using data from more than 10,000 dives by researchers and citizen scientists, as well as thousands of deep ocean trawls carried out by the National Oceanic and Atmospheric Administration (NOAA). They also found that the sunflower star die-offs were highly correlated with spikes in ocean temperature.
"The heat wave in the oceans—a product of increasing atmospheric temperatures—is exacerbating the sea star wasting disease," Drew Harvell, a fellow at Cornell's Atkinson Center for a Sustainable Future said in the UC Davis press release. "It's a lethal disease, and when you add a higher temperature to that, it kills faster, causing a bigger impact."
The sea star die-off began the same year as a massive marine heat wave, but, since ocean temperatures are not uniform, scientists were not able to determine if warmer water was directly impacting the sea stars and making them more susceptible to wasting disease, The New York Times explained.
By showing that the sunflower stars began to die closely after temperatures surged, the new research lends support to the hypothesis that heat did help trigger the outbreak.
"What's really exciting about this paper is the really strong correspondence between this temperature anomaly that occurred during that year when the sea stars started dying," Oregon State University associate environmental microbiology professor Rebecca Vega Thurber, who was not part of the research, told The New York Times.
Warmer temperatures have also been linked to the triggering of coral diseases, a fungus attacking frog and toad populations and the bacteria that wiped out two-thirds of saiga antelope, according to The New York Times and The Atlantic.
The sunflower star once proliferated along the Pacific coast and was vitally important to the health of its environment.
"This thing was as common as a robin," Harvell told The Atlantic. "You would go on a dive and always see sunflower stars."
In fact, the three-foot-diameter predator that can grow up to 26 arms and hunt sea urchins, clams and snails at a speed of six inches a second is known as a a "keystone" predator because of the outsized impact its presence has on the ecosystem it inhabits. Since its decline, unculled sea urchin populations have already begun to wreak havoc on kelp forests.
"Kelp forests along the West Coast have been hit hard, and are likely to diminish further as these sunflower-star predators become extremely rare," Carol Blanchette from the University of California at Santa Barbara told The Atlantic.
While the study's results are grim, the story of how it got its funding inspires a little more hope. When sixth-grade students at Carl Stuart Middle School in Conway, Arkansas learned about the sea star die-off five years ago, they felt inspired to do something about it, so they raised around $400 by making paper sea stars, complete with invented personalities, and asked people to adopt them for $1 each.
"We don't have an ocean anywhere close by," their teacher Vickie Bailey, now retired, told The Guardian. "The students knew that they would never go to the coast, they would probably never get to see this type of starfish, but they were so passionate about what was happening."
The students then sent what they had raised to Harvell at Cornell.
"I almost cried, I was so touched," Harvell told The Guardian. "So I matched it with $400 of my own and then one of our donors here put in a bigger amount of money and that's basically the funding that allowed us to do the initial survey."