The starfish are dying from "sea star wasting disease," an affliction that causes white lesions to develop, which can spread and turn the animals into "goo." The disease has killed up to 95 percent of a particular species of sea star in some tide pool populations.
"They essentially melt in front of you," Pete Raimondi, chairman of the Department of Ecology and Evolutionary Biology at University of California, Santa Cruz's Long Marine Lab, told The Santa Rosa Press Democrat.
Even starfish in an aquarium at the Gulf of the Farallones National Marine Sanctuary visitor center in San Francisco died from wasting disease after water was pumped in from the ocean in September.
Sampling has found the disease in starfish from Alaska to Southern California, according to a map on the marine lab's website.
Raimondi says wasting disease has never been as widespread as researchers are finding now.
In 1983-84, wasting disease hit Southern California but remained localized.
The disease usually affects one species, Pisaster ochraceus, an orange and purple starfish that grows up to 20 inches wide and is a staple of West Coast tide pools.
The starfish dine on mussels, so scientists worry that a collapse in the Pisaster population will allow mussels to multiply unchecked, crowding out other species.
Steven Morgan, an environmental science professor at the Bodega Marine Laboratory at the University of California, Davis, has found emaciated sea stars on the rocks at Schoolhouse Beach north of Bodega Bay, but was unsure if wasting syndrome was the culprit.
Still, Morgan found the starfish deaths a "strange anomaly."
"None of us had ever seen anything like this before," he said.