Cause of Mass Sea Star Die-Off Finally Identified

Written by on November 26, 2014 in Invertebrates, Marine Life

For over a year, scientists have been baffled by an unknown disease that has decimated sea stars along the North American Pacific Coast. Now, they finally know the cause.

Sea star wasting disease. Photo credit: <a href="">alisonleighlilly</a> via <a href="">photopin</a> <a href="">cc</a>.

Sea star wasting disease. Photo credit: alisonleighlilly via photopin cc.

Using specimens from the Natural History Museum (NHM) of Los Angeles County, Ian Hewson, microbiologist at Cornell University, and colleagues have identified the Sea Star Associated Densovirus (SSaDV) as the cause of Sea Star Wasting Disease (SSWD).

SSWD has been plaguing the Pacific coast since June 2013. It’s not pretty. Infected sea stars first develop white lesions, followed by decay of tissue around the lesions. Then, the sea stars’ bodies begin to break down, leaving dead, decaying starfish strewn across the sea floor. (You can see just how awful this process is in the video at the end of this post.) Affecting at least 20 different species of sea stars, it is the largest die-off of sea stars ever recorded. Knowing the source of the disease is critical, but scientists warn that the large-scale disappearance of many of these species will have a “serious and long-lasting ecological impact.”

“There are 10 million viruses in a drop of seawater, so discovering the virus associated with a marine disease can be like looking for a needle in a haystack,” Hewson said in a news release. “Not only is this the discovery of a virus involved in a mass mortality of marine invertebrates, it’s also the first virus described in a sea star.”

Samples from the NHM revealed that the virus has existed at a low level for at least 72 years. The researchers suggest that the disease may have reached epidemic levels due to sea star overpopulation, environmental changes, or mutation of the virus. They believe the virus can be transported by ocean currents, which contributed to the rapid spread.

Additional research will show how the virus infects and kills its host, and why it kills some species while others remain unaffected. Hopefully, researchers will also determine exactly what triggered the epidemic, which may help prevent or slow similar events in the future.

To learn more:

Copyright © 2014 by Marine Science Today, a publication of Marine Science Today LLC.

About the Author

About the Author: Emily Tripp is the Publisher and Editor of She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .


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