Mysterious Illness Threatens Oregon’s Starfish with Extinction

A leg of a purple ochre sea star disintegrates as it dies from sea star wasting syndrome. Ochre sea stars could go extinct in areas of Oregon’s coast due to a large outbreak of the disease. (Credit:Elizabeth Cerny-Chipman/Oregon State University)

A leg of a purple ochre sea star disintegrates as it dies from sea star wasting syndrome. Ochre sea stars could go extinct in areas of Oregon’s coast due to a large outbreak of the disease. (Credit:Elizabeth Cerny-Chipman/Oregon State University)

Along the west coast of the U.S. and Canada, starfish (or sea stars) have been dying off in massive numbers — succumbing to a mysterious illness researchers call sea star wasting syndrome. Now, this syndrome is threatening to wipe out populations of purple ochre sea stars (Pisaster ochraceus) along Oregon’s coast, which could have potentially devastating effects on the coastal ecosystem.

In April, less than one percent of ochre sea stars in Oregon were affected by the illness. Today, that number has exploded to an estimated 30 to 60 percent. Based on current trends, researchers at the University of Oregon predict the epidemic will only intensify. In some areas, nearly 100 percent of ochre sea stars could die.

“This is an unprecedented event,” said Bruce Menge, an Oregon State University marine biology professor, in a press release. “We’ve never seen anything of this magnitude before.”

Sea star wasting syndrome was first detected in June 2013, when Olympic National Park marine researchers noticed scores of sea stars off the coast of Washington were losing appendages, developing white lesions, and eventually disintegrating. The syndrome, which affects at least 10 different species including mottled star (Evasterias troschelii), leather star (Dermasterias imbricata), and six-armed stars (Leptasterias spp.), kills its victims in just a few days.

Ochre sea stars are a keystone species in Oregon’s intertidal ecosystem, responsible for maintaining biodiversity. They prey on mussels and sea urchins, keeping their populations in check. However, in the absence of sea stars, populations of these organisms will grow rapidly, smothering algae, other small invertebrates, and plant life including kelp and sea grass, which fish use for food and refuge.

The culprit behind the outbreak continues to elude researchers, but suspects include viruses, bacteria, environmental factors, or a combination. In the past, scientists attributed sea star die-offs to warming water temperatures, which leave the multi-armed creatures vulnerable to disease-causing bacteria. But that’s not the case here — water temperatures in Oregon are within the normal range. Currently, DNA samples taken from infected sea stars are being sequenced at Cornell University in an attempt to identify any infectious agents.

Researchers are still unsure of how extensive the damage will be and are continuing to monitor the situation. Some ecosystems that have suffered severe losses of sea stars have recovered in a short amount of time, while others feel long-lasting effects. To learn more about current efforts to stem the disease, check out the University of California-Santa Cruz’s Pacific Rocky Intertidal Monitoring Program.

Originally published at The Wildlife Society, June 13, 2014.

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