FILE: A sunflower sea star dwells underwater in California.

As an infamous marine heat wave ramped up more than a decade ago, sunflower sea stars fell sick and all but disappeared from California waters. 

But scientists refused to stop searching for the keystone species, Pycnopodia helianthoides, one of the world’s largest sea stars, known for hunting California’s rocky reefs with up to 24 arms. The loss of the big stars shifted California’s marine ecosystems wildly, including by allowing prey like purple sea urchins to gobble up collapsing kelp forests. 

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Last summer, a large group of research partners — including the Kashia Band of Pomo Indians, Greater Farallones and Cordell Bank national marine sanctuaries, the Nature Conservancy and Sonoma State University — gathered on the Sonoma Couny coast near Sea Ranch, investigating a cove where a diver had stumbled upon one wild sunflower sea star. They found 18.  

“For those who’d seen them prior to wasting disease, it must have been akin to seeing an old friend, but I felt more like a stunned paleontologist seeing a dinosaur,” Tyler Mears, a specialist for the Greater Farallones Kelp Restoration Project who was one of the scuba divers in the underwater search, said in a statement. 

Although there have been a few rare sightings in........

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