DAVID GREENE, HOST:
OK. If you can still fit in a beach trip before summer ends you may or may not notice that we are losing some swimming companions. Millions of sea stars, or you can call them starfish if you're not a marine biologist, have been quietly dying off. Deena Prichep reports on why.
DEENA PRICHEP, BYLINE: For over 30 years, biology professor Bruce Menge has been coming to Boiler Bay on the Oregon coast. As the sun rises and the waves crash, he checks the tide pools for sea stars but this year things look different.
BRUCE MENGE: You see how the arm is twisted like that? And see there is a white spot? That white spot is a lesion.
PRICHEP: It's the early stages of sea star wasting syndrome. Eventually they just dissolve.
MENGE: The first time we did our surveys we found about 1,400 animals; that was in mid-April. And now, last time we were over there, there are like 270. They're going fast.
PETE RAIMONDI: The first time that we really became aware that it was occurring was up in the Olympic Peninsula.
PRICHEP: Ecologist Pete Raimondi at the University of California at Santa Cruz has been mapping the outbreak. Those first cases showed up last summer.
RAIMONDI: And then we started seeing the same sort of symptoms down in Monterey and from those two points it popped up all up and down the coast.
PRICHEP: The disease has wiped out sea stars from Baja, California, all the way up to British Columbia. And reports are coming in from the East Coast as well. Now there have been other cases of wasting disease in the past but those were different. They hit just a few areas and Raimondi says, they were pretty clearly linked to El Nino.
RAIMONDI: We knew absolutely when the warm water turned off the disease would also turn off and that's not the case this time. And so this one's much spookier than in the past.
PRICHEP: What's causing this outbreak is a difficult question.
IAN HEWSON: There's roughly 10 million viruses per milliliter of seawater. There's a million bacteria per milliliter seawater. And this is the same seawater that floats through the veins of the sea stars.
PRICHEP: Microbiologist Ian Hewson is part of the team that's trying to figure out which of these millions of possibilities is causing the disease. But even if scientists find it they still need to know what's letting it take hold.
HEWSON: For example, you know, if we are under stress conditions we tend to get sick and the same thing occurs to animals in the marine environment.
PRICHEP: And that marine environment has lots of possible stressors for a sea star.
HEWSON: The oceans, as they absorb more carbon dioxide, are becoming more acidic. There's also temperature changes. There's also environmental pollutants. For example, everything from agricultural runoff through to little nano-particles put out by the pharmaceutical industry.
PRICHEP: Hewson says that figuring this out could take months, if not years, and by then the coast could look very different. Oregon states Bruce Menge says, cute little sea stars are actually predators. If they're not around, the things they eat like muscles could take over which can affect the whole ecosystem.
MENGE: The local diversity of a species will be greatly reduced in abundance or maybe eliminated.
PRICHEP: But there may be some hope. Menge says, that baby sea stars that hatched right when the epidemic hit are just starting to wash back in from the ocean.
MENGE: We think they are less affected by the disease than the big ones, so that is a possibility for a recovery.
PRICHEP: But while these little ones seem less affected they still do get sick. And so we still don't know whether the sea star population as a whole will recover - or continue to waste away. For NPR News, I'm Deena Prichep. Transcript provided by NPR, Copyright NPR.