ANCHORAGE, Alaska 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 starfish colonies up and down the West Coast.
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 the University of California, 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 said 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.
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.
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