The purple ochre sea star is facing extinction in Oregon due to an unknown disease that causes wasting away. The disease, although mysterious, hit the majority of the West Coast last summer but spared the Oregon coast. This year the state was massively affected.
In the past two weeks, the number of sea stars affected by the disease has skyrocketed. In April less than one percent of the sea star population was affected by the disease. By June the number had risen as high as 60 percent in some locations.
Scientists are calling the disease Sea Star Wasting Syndrome because of the effect it has on the marine creatures. Over the course of a week the star transforms from a healthy marine animal into a pile of limbs and even goo. It begins with behavior changes in which the sea star’s arms begin to cross as the sea star seems to collapse on itself. Next, while lesions appear on the sea star’s body that develop into holes, the skin begins to disintegrate around the lesion and the limbs begin to fall off. In some cases the sea star physically tears its own body apart. “It’s a pretty gruesome thing to see,” according to Bruce Menge, an Oregon State University marine biologist.
At the rate the purple ochre sea star is dying off in Oregon, the region could see a regional extinction within months, but it is not the only species to be wasting away due to the mystery disease. It has affected 10 different sea star species along the West Coast, including the sun star, which is also dying off in intertidal zones from Canada to Alaska. Menge called the die-off an unprecedented event, “We’ve never seen anything of this magnitude before.”
Scientists are still trying to determine the cause of the wasting disease. Menge said biologists have no clue as to the cause, or how long it might last, but it is very serious because the purple ochre sea star is a “keystone” predator that influences the diversity of life in the intertidal zone. They prey on other intertidal animals such as mussels, keeping their numbers from exploding to the detriment of other animals in the ecosystem.
Biologists are studying whether the die off is caused by a virus or a bacteria. They are also considering environmental stressors, like water temperature or salt content, making the organisms more susceptible to the wasting disease. Nothing definitive has turned up but they are hopeful of finding the cause.
Scientists are finding associations between certain viruses and microorganisms present in the lesions, according to Gary Wessel, of Brown University. He added that they are in the process of testing whether these microorganisms and viruses are causative or just associated. To do this, scientists infect healthy animals to see if they replicate the wasting phenotype.
Sea Star Wasting Syndrome is a mystery disease, causing Oregon’s purple ochre sea star population to waste away in rapid numbers. Scientists, however, are hopeful that with continued studies and testing, they will soon determine a cause. If a cause is not found, the intertidal ecosystem of the Oregon shore could change dramatically.
By Brandi M. Fleeks