Mystery of disappearing sea stars possibly solved

Densovirus likely responsible for millions of sea star deaths

By Angela Espinoza, News Editor

The mysterious disease that has eliminated millions of sea stars along the Northeast Pacific Coast (spanning Southern California, BC, and Alaska) has been revealed to likely be strains of a densovirus.

A strain of densovirus was suggested as the cause in a report published by the science journal Proceedings of the National Academy of Sciences on November 17. The report was initially filed for review in August, and approved of in October.

The effects of the virus result in the limbs of sea stars falling off, eventually disintegrating or “melting” the infected, effectively killing them. The virus has been widespread for over a year, wiping out many already diseased or ill sea stars.

However, Ian Hewson, microbiology professor at Cornell University in New York and one of the scientists who worked on the report, as referred by the Associated Press, stated that upon isolating the virus and injecting it into healthy sea stars, the virus killed them as well.

One important note the study found was that sea stars living in ocean water were the most likely to be affected. This was found after sea stars in aquariums in Vancouver and Seattle, which use seawater, became infected. In comparison, sea stars in aquariums that used ocean water under ultraviolet lights, which have the ability to kill outside viruses, were not infected.

The report also states that the virus already exists in the ocean and can be found in, amongst other sources, sea urchins and plankton, yet scientists do not know how the virus has caused such a devastating impact in recent years. A noted “population boom” in a specific species of sea stars may have increased the possibility of vulnerability amongst relatives.

In an interview with the Canadian Press, Hewson stated, “This very high number of sea stars in the Pacific Northwest leading up to this disease epidemic probably is what exacerbated the virus and made the switch between something relatively benign into something that was totally virulent.”

While scientists now know why sea stars are being infected en masse, the report concludes that there still remains the question of “how?” The virus and/or the sea stars had to change to some degree for the result of an already present disease to become an epidemic.

Besides concern for specific species’ extinction as a result of the virus’ spread, the disappearance of sea stars has caused an abundance of sea urchins in the ocean—which sea stars normally consume—resulting in changes for the ecosystem.

In total, this breakout has infected 20 species of sea stars and continues to kill many more.