Scientists zero in on cause of starfish die-offs – ‘It’s the largest mortality event for marine diseases we’ve seen. It’s been causing catastrophic mortality.’Posted by Jim at Monday, June 23, 2014
By Ashley Ahearn and Katie Campbell, Earthfix
17 June 2014
ORCAS ISLAND, Washington (PBS) – Drew Harvell peers into the nooks and crannies along the rocky shoreline of Eastsound on Orcas Island. Purple and orange starfish clutch the rocks, as if hanging on for dear life.
In fact, they are.
“It’s a lot worse than it was last week,” said Harvell, a marine epidemiologist at Cornell University. She’s been leading nationwide efforts to understand what is causing starfish to die by the millions up and down North America’s Pacific shores and on the east coast as well. It’s been called sea star wasting syndrome because of how quickly the stars become sick and deteriorate.
“It’s the largest mortality event for marine diseases we’ve seen,” Harvell said. “It affects over 20 species on our coast and it’s been causing catastrophic mortality.”
Scientists have been working for months to find out what’s causing the massive die-off and now Harvell and others have evidence that an infectious disease caused by a bacteria or virus may be at the root of the problem. The disease, they say, could be compounded by warming waters, which put the sea stars under stress, making them more vulnerable to the pathogen.
Harvell has studied marine diseases for 20 years. She had thought that the syndrome might spare Washington’s San Juan Islands. Until recently, pockets of cold water and swift currents seem to have protected the local sea star population from the epidemic.
But with the arrival of summer, the waters around the San Juan archipelago have warmed. From what Harvell and her team see as they survey beaches, there’s not much time for these starfish — or sea stars, as scientists prefer to call them since they’re not fish.
Harvell crouches in the sand and points at a withering orange pisaster ochraceus, or ochre star, one of the most common sea stars found in the intertidal zones of the West Coast. One arm is curled over on itself, another hangs by a thread of gnarled flesh.
“The whole arm is flat. It looks dried out, wasted, thin, deflated. Sea stars are not supposed to look like that,” Harvell said. “My expectation is that within the next month all of the stars will die.” [more]