Environment & Science

Scientists identify clue in widespread deaths of sea stars

A sea star at Crystal Cove State Park in Laguna Beach has lost three arms, possibly as a result of wasting disease.
A sea star at Crystal Cove State Park in Laguna Beach has lost three arms, possibly as a result of wasting disease.
Jed Kim

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Scientists may have discovered a key answer behind the mysterious disease that has wiped out millions of sea stars along the Pacific Coast from Mexico into Canada.

A study published on Monday in the Proceedings of the National Academy of Sciences finds a strong correlation between a type of parvovirus found in many invertebrates.

"There’s just one type of virus that keeps coming up again and again and again in sick sea stars, but you don’t find it very often in healthy sea stars. And when you do find it in healthy sea stars, those sea stars eventually become sick," said Kevin Lafferty, a marine ecologist with the United States Geological Survey who was one of the authors of the study.

Scientists are referring to the virus as Sea Star Associated Densovirus. Lafferty, who is also an adjunct professor at UC Santa Barbara, said it’s the first time a virus has been associated with the devastating disease.

"This is a new type of association that we’ve never seen. It sort of opens our eyes, I think, more to disease dynamics in the ocean, which is a place that people really haven’t thought about disease very much," Lafferty said.

Scientists were able to infect healthy sea stars with fluids from sick sea stars, causing the virus to propagate within the new hosts.

Despite the evidence of contagion, scientists were careful to state that the virus has a strong link to the syndrome but didn’t outright name it as the cause.

"There is still a lot to work out in this system," said Pete Raimondi, a professor of ecology and evolutionary biology at UC Santa Cruz.

Raimondi, also an author on the study, said that researchers believe the syndrome is likely to be caused by a combination of pathogens and environmental stressors such as higher temperatures.

That theory is helped by the fact that researchers found the densovirus in specimens at the Natural History Museum of Los Angeles County. Some were found in samples that were 70 years old. Raimondi said that the long-term presence of the virus in local waters makes the disease pathway intriguing.

"It’s a lot easier to understand why an exotic pathogen can come in and wipe out individuals, because they’re not used to it. They haven’t evolved with it, and so they don’t have any built up immunity to it," Raimondi said. "When you have something that has been around for quite a long time, and causes this sort of issue, then it brings up all sorts of questions that I think are really important."