Sea Stars Dying in Tide Pools

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A seagull at Treasure Island dining on the remnants of a sea star killed by wasting disease now spreading along the West Coast.
A seagull at Treasure Island dining on the remnants of a sea star killed by wasting disease now spreading along the West Coast.

At least 40 visible sea stars were alive and well in the Treasure Island tide pools in South Laguna at noon this past Saturday. But by 3 p.m., eight had disintegrated like wet bread.

An epidemic, which has destroyed sea stars along the West Coast beginning last June, has reached the shores of Laguna Beach.

Snorkelers reported finding sea star legs piling up in underwater rocky crevices near Crescent Bay and Shaw’s Coves in North Laguna and rolling eerily along the ocean bottom.  The limbs will eventually wash up on shore.

Of 76 sea stars spotted last Sunday at Treasure Island, a quarter of the population exhibited signs of what scientists have named sea star wasting disease, said Jeff Rosaler, director of education and research at the Laguna Ocean Foundation and a Treasure Island tide pool educator.

A dead sea star's disembodied leg floats to the surface of a tide pool at Treasure Island in South Laguna.
A dead sea star’s disembodied leg floats to the surface of a tide pool at Treasure Island in South Laguna. Photos by Jeff Rosaler. 

Scientists categorize sea stars as a “keystone” species, which means they keep their prey – mussels, snails and urchins — in check.  Without them, as with the extinction of other species, the balance of nature runs amuck. Urchins have been known to overpopulate and do deadly damage to local kelp forests.

In the tide pools on Sunday, observers watched as legs fell off the sea stars, their bodies split in half, small lesions became rips in the sea stars’ spiky skin, and white flesh and orange gills spilled out.

An octopus, about 15 inches long, crept out from under a nearby rock and tore a dangling leg off a melting sea star. The next day, only the empty external skeleton of two limbs remained. Seagulls fought and feasted over other dismantled sea stars lodged in rock crannies.

While the affliction is not an anomaly, scientists are stumped and finding the massive outbreak “particularly troubling,” said Pete Raimondi, of UC Santa Cruz, who is the lead investigator into the disease.

In the past, unusually warm water caused the wasting of sea stars, particularly during an El Nino, but that’s clearly not the case this time, said Raimondi. “That’s what’s so concerning about this. In the past, when the die-off was associated with warm water, you had this idea that things would get back to normal. But it’s not warm water. We’re in a cool water period.” Sea stars usually thrive in normally cool Pacific Ocean temperatures.

Also disturbing to Raimondi is how far the disease is spreading and the number of sea stars it’s affecting.

The culprit is believed to be an infectious microorganism, which appears to be attacking a specific marine species and would not likely affect humans, scientists say. Raimondi said researchers are “pretty clear” what the infectious agent is but they are unsure of its origin and decline to disclose whether it’s naturally occurring or manmade.

“These guys are epidemiologists and they have a protocol that they follow,” said Raimondi.  ”They don’t release anything until they follow the protocol. They’re in the process now of challenging organisms.  Once that work is done, they’ll be able to release the information.”

The sea star death-rate along the West Coast was described as “catastrophic” by Ian Hewson, an assistant professor in microbiology at New York’s Cornell University, who is collaborating with Raimondi in collecting data and testing possible causes of sea star wasting. Raimondi contributed to a report released last month, published by UCSC’s ecology and evolutionary biology department’s Pacific Rocky Intertidal Monitoring project.

Hewson is overseeing experiments at UCSC and the University of Washington to establish the suspected cause of the disease. Scientists are inoculating two healthy sea stars with possible infectious agents.  If healthy sea stars also contract the disease, which could be as soon as two days, the cause will then be definitive and results will be published in scientific journals before being released to the public, which could take up to six weeks.

Tsunami debris and radioactive fallout from the Fukushima nuclear power plant melt-down in Japan have not been entirely ruled out as a cause Hewson said, but Raimondi called it unlikely.

“The path of the debris and presumably the radiation is far to the north of here,” said Raimondi. “It’s mostly in the Pacific Northwest. No one’s been able to detect levels of radiation that are even above background in North America. There’s no possibility at this point that the stuff has gotten here.”

Hewson added that human pollutants are also being considered. “The ocean is really subject to a great deal of human influence,” he said, “everything from run-off and fertilizer use to actual toxicants in various products and treatments that end up in the sea. We haven’t been able to disprove any of these pollutants as a cause.”

Signs of the current epidemic in Laguna were noticed last fall, when water temperatures were more summerlike, hovering around 70 degrees, said Laguna Ocean Foundation’s chair, Louise Thornton.

Over the past two weeks, the mortality rate has become epidemic, said Rosaler, the tide pool educator.

Former episodes of the wasting disease occurred in the early 1980s and late ‘90s. Warm El Nino currents washed in from Mexico and destroyed sea stars as well as the local kelp forests, which were scavenged by ravenous sea urchins that had lost a once-abundant food source.

Biologist Nancy Caruso, who helped replant the 100-acre kelp forest now flourishing off Laguna’s coastline, doesn’t expect a surge in the urchin population or damage to kelp forests because of the die-off of sea stars.

“I don’t see anything going on with the kelp,” she said.  “It’s a stress-induced problem with the sea stars and we need to figure out what the stress is.”


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