Environment: Study tracks recovery of Oregon sea stars after massive wasting disease epidemic

Scientists say some species may recover quickly

Northern rainbow star afflicted with sea star wasting disease. This species had virtually disappeared from central California kelp forests as of February 2014. Photo: Steve Lonhart / NOAA MBNMS
A northern rainbow star afflicted with sea star wasting disease. This species had virtually disappeared from central California kelp forests as of February 2014. Photo courtesy Steve Lonhart / NOAA MBNMS.

Staff Report

Sea stars along the Oregon coast are recovering from a widespread die-off caused by a viral disease, scientists have reported in a new study published May 4 in the journal PLOS ONE.

The researchers took a close look at the sea star wasting epidemic, which affected 20 species from Baja California to Alaska, making it among the largest marine epidemics on record. They found that, in Oregon, the disease occurred during a phase of cool water upwelling along the coast and so wasn’t directly linked with the over-heated “blob” of Pacific Ocean waters that persisted off the West Coast of the U.S. the past few years.

“In contrast to other locations along the US west coast, sea star wasting disease increased during a period of cool, not warm temperatures, suggesting that the cause of wasting outbreaks is multifactorial,” said study author Bruce Menge, of Oregon State University. “Although up to 84 percent of local populations died, a massive recruitment of sea stars occurred the following spring, suggesting the possibility of rapid recovery,” Menge said.

The rapid spread of the wasting disease shocked researchers. Afflicted sea stars lost arms and legs and sometimes disintegrated entirely within a few hours of first showing symptoms. The epidemic reached Oregon in April 2014 and spread along most of the coast by June, infecting about 90 percent of sea stars.

The researchers were able to use data from on-going long-term monitoring to assess the effects on sea stars as well as mussels living in the rocky intertidal habitats. They found that as many as 80 percent of the populations died at the study sites during the epidemic. The wasting disproportionately affected adults over juveniles, and sea stars in tide pools.

Sea stars are keystone predator species that play a major role in balancing their local ecosystems. And by the spring of 2015, the researchers saw the population starting to recover. Some of the study sites had up to 300 times as many new sea stars as in 2014.

The recovery may be due to the increased availability of small prey, like mussels, resulting from the previous year’s sea star loss. The authors hope that these efforts will aid in calling for a coast-wide investigation of how the wasting epidemic affected intertidal communities along North America’s western shores.

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