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If you have explored any tide pools lately you probably know that the once-ubiquitous Pacific sea stars have largely disappeared along our coast — and those that remain often have lesions, missing limbs or show other signs of major disease. The cause of the fast spreading enviro damage has been a mystery, but now scientists from Cornell, UC Santa Cruz, the Monterey Bay Aquarium and other institutions have identified a virus that seems to be connected. The virus has been detected in Pacific sea stars as long ago as 1942, and the researchers aren't sure why the situation has turned so deadly now. From the Santa Cruz release:
All along the Pacific coast of North America, the sea stars have been disappearing. Commonly known as starfish, millions have died over the past year in an unprecedented outbreak of sea star wasting syndrome, a mysterious disease that causes sea stars to disintegrate as their arms fall off and tissues turn to mush.
Now, scientists have found a potential culprit, a previously unidentified virus that is prevalent in symptomatic sea stars. In a paper published November 17 in the Proceedings of the National Academy of Sciences, researchers at Cornell University, UC Santa Cruz, and other institutions reported evidence linking the disease to a densovirus, a type of parvovirus commonly found in invertebrates. The paper includes a genomic analysis of the newly discovered "sea star associated densovirus" (SSaDV)…"The fact that it has occurred historically indicates that while this virus may be the agent that causes the disease, something may have happened recently that caused it to go rogue, because we've never seen anything like the current outbreak," [UC Santa Cruz professor Peter] Raimondi said. Initially, researchers suspected that warm water played a role in triggering outbreaks, but that now seems unlikely to be the cause across the range of locations that have been affected, he said.
From a story in the San Jose Mercury News:
Marking a major breakthrough in the mystery of one of the largest wildlife die-offs ever recorded in the world's oceans, scientists believe they have found the cause of a disease that has killed millions of starfish since last year along California and the Pacific Coast.
The epidemic, which threatens to reshape the coastal food web and change the makeup of tide pools for years to come, appears to be driven by a previously unidentified virus, a team of more than a dozen researchers from Cornell University, UC Santa Cruz, the Monterey Bay Aquarium and other institutions reported Monday….The outbreak, known as "wasting syndrome," has infected at least 20 different species of starfish since it was first detected in Washington's Olympic Peninsula in June 2013. It spread to Oregon, Monterey Bay, Big Sur and as far south as Baja California, even killing starfish in major aquariums in Seattle, Vancouver, Monterey and other cities.
When infected, starfish at first become sluggish, then develop white lesions. Within days, they curl up and parts of their arms break off, sometimes literally crawling away. Not long after, the entire starfish turns into a gooey mess and dies.
Heal the Bay staff scientist Dana Roeber Murray has posted a blog entry explaining the news and how the public can help by reporting signs of sea stars wasting away.
Once abundant in our tidepools and rocky reefs, millions of sea stars have wasted away and disappeared along our coast. Just last weekend as I went tidepool exploring at Leo Carrillo State Beach during a minus tide, we encountered octopuses, sea hares, urchins, and little fish -- but not a single sea star. This time last year, the scene included missing limbs … melting masses of flesh … gooey lesions overtaking the entire body. Divers and tidepoolers encountered numerous sea stars with white lesions that eventually decomposed body tissue into a goo-like blob….
Scientists say that the virus is different from all other known viruses infecting marine animals, and they’ve named it “sea star associated densovirus.” The progression of symptoms can be very rapid, with initial signs leading to death within a few days. Figuring out marine diseases and identifying what virus is to blame is difficult because one drop of seawater can contain 10 million viruses. Researchers had to sort through millions of marine viruses to identify the culprit.The identified densovirus weakens the sea star’s immune system, making it more susceptible to bacterial infections, such as sea star wasting disease, a fast-moving scourge that has occurred along our coast for decades, but not at the recent widespread level. Reports of disintegrating sea stars have come from as far north as Anchorage, Alaska, to our shores along Palos Verdes, and down south to La Jolla. The current epidemic began in Washington in June 2013; since then at least 12 different species of sea stars and even some purple sea urchins have been found as victims. By the fall of 2013, the disease had become widespread along the Pacific coast.
Sea stars, in particular ochre stars, are an important keystone species that have the potential to dramatically alter rocky intertidal community composition. Removal of this top predator from intertidal ecosystems can affect the whole food chain. After past wasting events, ochre stars were absent along Southern California’s shoreline for years.
Heal the Bay says that scientists are asking the public to keep an eye out for infected sea stars and urchins. "If you see any possible infections while out in our local intertidal and subtidal seas, please report your findings to seastarwasting.org."
Photo: UC Santa Cruz
