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Following a Devastating Pandemic, California’s Sea Stars are Evolving

June 19, 2018

In 2012, Environmental Systems graduate student Lauren Schiebelhut was collecting DNA from ochre sea stars living along the Northern California coast — part of an effort to study genetic diversity in various marine species that serve as indicators of habitat health. She had no idea that just one year later, most of the sea stars would be dead.

The culprit was sea star wasting disease (SSWD), a marine pandemic whose 2013 outbreak decimated sea star populations in waters up and down the west coast of North America.

The disease, which turns the sea star’s normally rigid body into a gooey blob, claimed 81 percent of ochre sea stars along the hundred-mile stretch of coast just north of San Francisco where Schiebelhut works — now as a postdoc in UC Merced Professor Michael Dawson’s lab.

“They go from a hard candy to a marshmallow,” Dawson said of symptomatic sea stars.

While it remains one of the worst marine pandemics ever recorded, the SSWD outbreak had an unexpected silver lining: It provided scientists with a natural experiment in evolution and an opportunity to explore how a species responds to a cataclysmic population collapse.