Sea star wasting syndrome has struck before on the West Coast – during El Niño events when ocean temperatures are warmer than usual in the eastern Pacific.
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Despite the lack of El Niño, the water in the northeast Pacific has been warmer than usual for months, which can have an impact on sea stars and disease. We know that outbreaks of marine disease coincide with unusually warm sea surface temperatures.
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Last winter when news media speculated about a connection between the Fukushima nuclear disaster and the sea star die-off, researchers at UC Santa Cruz, who have been monitoring Pacific tide pools for decades, posted on their Sea Star Wasting Syndrome Updates page that, “there has been substantial speculation in the media that the disease could be a result of increased radiation from the nuclear power plant disaster in Fukushima, Japan. We have no evidence to suggest that radiation is a likely culprit.”

Smithsonian sea star expert Chris Mah (@echinoblog) went into more detail about the lack of connection between the Fukushima nuclear disaster and the sea star die-off in a post at Deep Sea News. He explained that sea star wasting syndrome predates the nuclear disaster, that sea star wasting is found in the Atlantic as well, and that no other life in the tide pools appears to be affected besides the stars.