Allison Gong often keeps live sea stars for her college biology classes at CSU Monterey Bay. Early this fall, however, she was alarmed to find her animals eating each other. Even worse, they were beginning to disintegrate.
“Healthy stars don’t get eaten by other stars, so seeing cannibalism always raises the ‘uh-oh’ flag,” says Gong, associate research biologist at UC Santa Cruz’s Long Marine Laboratory. “Then, the stars began dropping arms and melting away.”
Gong’s sea stars, commonly known as starfish, were affected by sea star wasting disease. The symptoms were first described in 1978, and several outbreaks have occurred since. Now, the wasting sickness has arrived in Monterey Bay.
“The disease is very grisly,” says Amanda Bates, a lecturer at the U.K.’s University of Southampton. “The fleshy tissue of the animal is presumably damaged by the infection and breaks down. Essentially, it’s a flesh-melting disease.”
Gong was appalled and slightly fascinated as she watched her sea stars develop white lesions, become soft and mushy and slowly lose their limbs. As Gong’s sea stars were pulling themselves apart, their fellows along the North American coast were engaging in the same activity.
“The sea stars began dropping arms and melting away.”
Over the past few months, scuba divers in British Columbia as well as researchers in Alaska, Washington and California have reported hundreds of melting sea stars from at least 10 different species. The timing of these outbreaks suggests they are connected, and researchers are concerned about the potential regional impacts.
“One of the affected species is Pisaster ochraceus, the ochre star,” Gong explains. “This star is a keystone species; its absence causes a change in the makeup of the biological community.”
Researchers are still scratching their heads over the cause. The outbreaks appear to be connected to an extended period of warm ocean temperatures over the summer. “We don’t yet know what agent or combination of agents is causing the symptoms,” Bates says. “The only way I found to control the disease was to move animals to cooler temperatures.”
Although infected sea stars have been found in Santa Cruz and Big Sur, the disease may not yet be prevalent in Monterey. Steven Litvin, research coordinator of the Marine Life Observatory Program at Stanford’s Hopkins Marine Station in Pacific Grove, hasn’t seen any despite research that often takes him underwater.
“If you see sick stars,” Litvin says, “the best thing to do is report it. Here at Hopkins, we have asked everyone doing field work to keep an eye out.”
10/31/13 UPDATE: As of late this week, researchers at Hopkins Marine Station report numerous sick sea stars in the kelp forest adjacent to the Station, confirming sightings earlier this month by recreational divers in the area. -DLG