A couple of years ago, divers in Puget Sound began to notice something odd: Starfish were disappearing.
The sea creatures would get sores and then melt into piles of mush. Sea star wasting syndrome is a gruesome disease and it spread to starfish all along the West Coast. Scientists still don't know a lot about it.
Katie Campbell, a reporter for EarthFix and KCTS, says that although scientists have isolated the cause, the creatures continue to die.
“At a site near Bellingham, they went out in the winter this past winter and found there were 400 stars at one site,” Campbell told KUOW’s Marcie Sillman. “They just went back last week and found there were just 100 left."
Researchers know what’s killing the sea stars: sea-star associated densovirus. This discovery was a coup, as one drop of seawater contains more than 10 million viruses. This particular virus had been in the water for decades – researchers have evidence of it going back to 1940.
“What sparked this virus – that was seemingly benign – to transform into this perpetrator of what's considered the largest marine disease outbreak ever recorded?" Campbell says.
Some believe the wasting disease is linked to warmer water. That could stress the sea stars and make them more susceptible to infection. Others blame ocean acidification.
“We know more about how shellfish are adversely affected from low pH conditions, because they calcify,” Campbell says. “People may not realize that sea stars also have kind of a hard, calcified skin that protects them from predators, but in low pH conditions that may be causing them some problems too.”
Sea stars haven’t been studied much because they’re not moneymakers. But they are considered a keystone species.
“You might not think about them as being these major predators, but they are. They eat tons of mussels and sea urchins and crabs,” Campbell says.
“When you take a predator out of an ecosystem, the populations they had been eating can grow much more quickly. That shifts the whole biodiversity of that ecosystem.”
Divers say they’re seeing herds of green sea urchins. It’s unclear if that’s because starfish aren’t eating them – or if they’re coming out of hiding because the starfish won’t get them.
“When you pull a large predator out of an ecosystem the cascading effects are everywhere,” Campbell says.