Scientists Say They Have Solved the Mystery of What Killed More Than 5 Billion Sea Stars

Researcher Alyssa Gehman from the Hakai Institute counts and measures sunflower sea stars in the Burke Channel on the Central Coast of British Columbia, Canada, in 2023. Bennett Whitnell/Hakai Institute via AP

WASHINGTON—Scientists say they have at last solved the mystery of what killed more than 5 billion sea stars off the Pacific coast of North America in a decade-long epidemic.

Sea stars—often known as starfish—typically have five arms and some species sport up to 24 arms. They range in color from solid orange to tapestries of orange, purple, brown and green.