After Die-Off, Sea Stars Face Uncertain Future

Feb 13, 2017

A researcher examines an ochre star with whitened arms — a symptom of sea star wasting syndrome. So far, about 20 different species along the Pacific Coast appear to be vulnerable to the disease.
Credit Greg Davis

Sea star wasting syndrome was first documented in Kachemak Bay in 2014, but it wasn’t until last summer that the mysterious infection began killing sea stars in large numbers.

Nearly six months later, the long-term effects of the die-off remain unclear.


Katie Gavenus is a Masters student at the University of Washington. She began monitoring sea stars in Kachemak Bay in 2014 as part of a project with the Center for Alaskan Coastal Studies.

Even to the trained eye, the first signs of sea star wasting syndrome are easy to miss.

“There tend to be these white lesions. It kind of looks like it could be scars or raw spots from a bird pecking at it,” said Gavenus.

In 2014, most of the sea stars in the areas she monitored appeared healthy, with only about 10 percent showing signs of wasting syndrome.

Last summer, the infection appeared to spread. Gavenus watched as true stars, the classic five-armed species, died in record numbers. In many cases, the dying sea stars lost multiple arms.

“It was pretty eerie actually. We saw a lot of dismembered true star arms floating around. If the currents and the waves were just right, you’d get this line of true star arms along the surf line on the beach,” she said.

Other species, like the sunflower star, dissolved into what she calls a “pile of goo.”

“What you started to see were piles of what looked like someone had taken a sunflower star and put it in a blender and poured it out into a crevice in the tidepool,” said Gavenus.

Sun stars (Pycnopodia helianthoides) appear to be particularly vulnerable to sea star wasting syndrome. Infected individuals can disintegrate rapidly, often losing multiple arms. Here, a healthy sun star photographed in Kachemak Bay (at left) is shown next to an infected sun star (right).
Credit Dorle Harness / KBBI

Infected sea stars have appeared along the Pacific Coast since the 1970s, but the extent of this latest outbreak – stretching from Baja California to Alaska – is new.

In 2014, researchers identified a virus in infected sea stars. However, they also found the virus present in preserved museum samples dating back to the 1940s – long before the outbreak began. That suggests there might be other factors contributing to the outbreak, such as changes in temperature or pH.

Another big unknown is how the loss of sea stars will affect intertidal habitats as a whole. Because sea stars are important predators of other marine invertebrates, like urchins and mussels, their disappearance could have cascading effects on species diversity.

“The big thing that I take away from all this is that there’s a lot that we do not yet know. It’s pretty fascinating to look at a lot of the connections and very humbling to realize that there’s a lot more that’s going on out there than we grasp right now,” said Gavenus.

Staff with the Center for Alaskan Coastal Studies returned to monitoring sites in Kachemak Bay in late January. While they didn’t see any signs of the disease, they also didn’t find any true stars or sunflower stars – two of the species hit hardest by wasting syndrome last summer.

Because sea stars often retreat to deeper waters in the winter, it's unclear whether these preliminary surveys are representative of sea star population trends in the region.

Coastal Studies staff and local volunteers plan to continue tracking sea star populations in Kachemak Bay throughout the year.