A disease that began killing millions of sea stars along the West Coast last fall has reached public aquariums in Western Washington.
Point Defiance Zoo & Aquarium has lost more than half of its 369 sea stars — commonly known as starfish — to the disease, which is comparable to the mortality rate in the wild, said Neil Allen, curator of aquatics at the Tacoma aquarium.
Seattle Aquarium staff members started noticing sick sea stars in early July in tanks where visitors can touch the starfish. Eventually the aquarium lost hundreds of sea stars in its exhibits, including all of its 43 sunflower sea stars.
The grisly disease starts with the creature’s limbs contorting in unnatural ways. White lesions appear on the body, the limbs tear off and the sea star deflates.
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“We have to suspect that it’s causing pain even though we don’t know (for certain),” said Lesanna Lahner, staff engineer at the Seattle Aquarium.
There is no evidence the disease is transmissible to humans but the sea stars were taken out of the Seattle Aquarium exhibits to prevent other starfish from contracting the syndrome, she said.
The sea stars are monitored throughout the day and night. When signs of the disease become noticeable, the starfish are quarantined in a back room where the water is more filtered than usual, she said.
Keystone species in the wild
One reason scientists are worried about the problem is that sea stars are what’s known as a keystone species, meaning their survival is important to the ecosystem around them.
“(Sea stars) are such a key player in keeping our ecosystem healthy,” Lahner said. “We depend upon a healthy ecosystem for a variety of things like commercial fishing and recreational activities.”
Sunflower stars — among the least resilient — are considered keystone predators because the ecosystem relies on them to eat things like mussels, which aren’t preyed upon by many other predators, she said.
Because of deaths of such keystone predators, the mussel populations have grown substantially, Lahner said. That could result in an overpopulation allowing mussels to take over less hardy species.
It’s hard to know how the deaths of the sea stars will affect the ecological system, she said, but there could be big changes in the local wild marine life.
An unprecedented magnitude
Similar occurrences of what’s known as sea star wasting syndrome occurred in the 1970s, 1980s and 1990s, but were not this widespread, according to the Ecology and Evolutionary Biology website for the University of California Santa Cruz.
In past, the disease struck so quickly that by the time the outbreaks were apparent they were nearly over, Lahner said. Now, the disease has been spotted for more than a year.
The current incidence of the disease was first noticed in ochre sea stars in June 2013 along the coast of Washington. It then spread along the West Coast with some cases sprouting in East Coast waters.
The ferocity and vastness of the disease has stumped scientists, but they aren’t at a total loss for answers, Lahner said.
There’s concern that a change in the coastal saltwater could have activated a deadly pathogen or made the sea stars more susceptible to a pathogen, she said.
Local aquariums are working with more than 85 collaborators to find the cause and a solution to the disease, Lahner said.
“We’re trying really hard but it’s a really complicated puzzle to put together because there’s no real foundation (of knowledge about) the sea stars, so it’s hard to tell what’s normal,” she said.
While no sea star species is 100 percent resilient to the disease, leather-bodied stars seem slightly more resistant, she said.
Leather and blood starfish have a rubbery outer coating and signs of the disease showed up much later in these sea stars than in sunflower and ochre stars ,whose fleshy bodies seem less resistant, Lahner said.
Some aquariums are using an antibiotic to treat sick sea stars, but there’s debate over whether that’s the best solution, she said.
“It’s a broad spectrum antibiotic so it’s either killing the primary infection or a secondary infection as a result of the disease,” she said. “Some are worried that treating the sea stars could create a resistant superbug.”
After consulting with colleagues along the West Coast, Point Defiance decided to treat its sea stars, Allen said The hope is to add to the knowledge and research regarding the disease and how to combat it.
Point Defiance fights back
Point Defiance staff members noticed the disease in their sea stars six months ago, Allen said.
At first the disease was killing the starfish so quickly there was no time for treatment, he said. Once treatment was begun it seemed to slow the disease, though not necessarily cure the creatures, Allen said.
“Initially you don’t know what’s going on,” he said. “You don’t know which ones are sick and which ones aren’t. Their arms get contorted. It looks like they have arthritis and once we see that, we know they’re affected.”
The sea stars were taken out of the touch tanks two months ago. Point Defiance removed the sick starfish from the exhibits, but more than 120 healthy ones still are on display, Allen said.
Staff members have not noticed the syndrome in other marine animals.
The Seattle Aquarium has lost much of its collection, but visitors still can see healthy sea stars, Lahner said.
Neither the Seattle nor Tacoma aquariums plans to collect wild sea stars to replace those that died.
“There’s no point in bringing a sick sea star into the exhibits,” Allen said. “We’re going to wait until this resolves itself one way or another.”