A decade-long mystery has finally been solved: what killed more than 5 billion sea stars off the Pacific coast of North America? Researchers have identified a bacterial culprit that caused the devastating epidemic.
The outbreak, which started in 2013, ravaged over 20 species and left the sunflower sea star population dwindling by 90% within its first five years. Marine disease ecologist Alyssa Gehman helped pinpoint the cause, describing how the wasting disease leads to lesions and arms falling off.
The findings reveal that Vibrio pectenicida bacteria were responsible for the outbreak. This bacterium has also infected shellfish. While it took over a decade to identify the cause, researchers have now found a solution.
“This solves a long-standing question about a very serious disease in the ocean,” said Rebecca Vega Thurber, a marine microbiologist at University of California, Santa Barbara. The discovery will aid in the recovery efforts, enabling scientists to test which sea stars are still healthy and consider relocation or captive breeding programs.
Healthy sea stars help regulate sea urchin populations, preventing them from overpopulating kelp forests that support numerous aquatic species, including fish, sea otters, and seals. With more information on the disease’s cause, researchers aim to restore sea star populations and regrow kelp forests.
Source: https://phys.org/news/2025-08-scientists-mystery-billion-sea-stars.html