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Amid symptoms of starfish die-off, researchers look for a cause

Devin Kelly
Anchorage Museum image

In the aquarium at the Anchorage Museum, starfish, silent and slow, cling to rocks and wait to be lifted out of the tank for petting.

These five-armed creatures hardly seem prone to ecological drama. But last fall, the museum's starfish started showing signs of a disease that scientists say is killing massive numbers of starfish colonies up and down the West Coast.

Symptoms of sea star wasting syndrome, as it's called, have been reported as unnatural twisting of the arms and white lesions on the surface of a starfish's skin. A speedy death comes after a loss of arms and softening of tissue.

Along the West Coast, the population of starfish is estimated to be in the tens of millions. With limited data, scientists don't know how many have succumbed to the disease, but it may be in the tens of thousands to the low millions, said Pete Raimondi, a professor of ecology and evolutionary biology at UC Santa Cruz and the principal investigator on the Pacific Rocky Intertidal Monitoring Group.

Similar die offs have occurred before, but an event of this magnitude has never been documented, scientists said. Its presence has been reported as far south as San Diego.

In Alaska, evidence of sea star wasting was first observed last summer on Kayak Island, a remote island in the Gulf of Alaska, Raimondi said. His group was working with the Sitka Sound Science Center to conduct coastal biodiversity surveys.

On the island, a number of diseased sea stars were discovered, trumping an earlier theory that the illness was linked to warmer water, Raimondi said.

"It was the last place on earth where we would have expected to see it," Raimondi said.

Researchers took pictures and left, and at that point, the illness started showing up all over the West Coast, he said.

On a recent morning, Anchorage Museum curator Greg Danner walked into a back room where sick animals are isolated for treatment and care. Nicole Abeln, the animal care technician, pulled out a white binder labeled "Sea Star Wasting Disease Information and Logbook."

She opened it up to a chart.

"Collections trip in Whittier. 1 mottled sea star twisted and looking deflated," reads one entry from Aug. 25. That seastar was eventually euthanized.

The museum euthanized a total of 8 sea stars between August and November. Symptoms ranged from white lesions of the arms to a sea star that lost two arms during the day. Museum staff had never seen anything like it.

But since November, the disease seems to have vanished again, Danner said.

He said that changes the museum made to its aquarium practices -- namely, controlling tank temperature by limiting the number of hands in the water -- may have made a difference. But it's hard to tell.

"We're in the same mystery boat as the rest of the world," he said.

Raimondi, the Santa Cruz researcher, said that the symptoms appear to be highly present among starfish in captivity. That could be a sign that stress was manifested more quickly, he said.

Raimondi also said that the term "wasting" applies to symptoms. These symptoms are actually seen all the time, he said, and are attributed to stress, such as a starfish drying out or getting sick.

"The difference here is that when you see it, it's present in animals that are where they should be, rather than washed up on a beach somewhere," Raimondi said.

The science so far appears to indicate that species are affected differently depending on physical location. For sea star species in tide pool areas, the lesions or sores show up, followed by tissue decay, Raimondi said. Death might follow in a matter of weeks, or not at all.

But in underwater species with less physical structure in the environment, the results are catastrophic and quick, Raimondi said. Decay happens in hours or a day, rather than weeks.

Over at the Sitka Sound Science Center, Taylor White, aquarium director, said that she and fellow researchers haven't seen the wave of impacts described in the Lower 48.

"It's honestly not that extreme up here," she said. She echoed Raimondi in noting that the symptoms observed in association with the disease, including twisting, are also common sea star reactions to stress.

But she added that researchers in Sitka hope to get a baseline of data in order to track the disease. In general, very little research has been conducted in Alaska as far as underwater areas, Raimondi said, but that's about to change.

In March, Raimondi's team will return to Sitka Sound and sample established survey plots, with a focus on broadening data related to seastar wasting syndrome.

Around that time, a diving class with the University of Alaska, Fairbanks bound for Kachemak Bay plans to keep an eye out for affected sea stars, said Barbara Konar, a professor of marine biology at UAF.

Raimondi said scientists are close to identifying the cause of sea star wasting syndrome. A pathogen appears to be the most likely culprit. Raimondi said, and there does not appear to be a link between the wasting and radiation leaked from Fukushima nuclear plant disaster, as some have speculated.

Yet, if a cause of the disease is identified, another uncertainty remains: how to stop it.

"Is it the type of thing that will heal itself over time? That's the real question," he said.

Reach Devin Kelly at dkelly@adn.com or 257-4314.

Editor's note: An earlier version of this story misspelled the last name of Anchorage museum curator Greg Danner.

 


By DEVIN KELLY
dkelly@adn.com