Marine scientists say the sea stars are under attack by an unknown wasting disease that turns their bodies to goo, and the results are gruesome, nasty and grisly.
All along the Pacific coast, sea stars are experiencing their largest known die-off, which is affecting more species of sea stars than any other attack in recent memory, biologists said. A smaller and isolated Atlantic outbreak, at points off Rhode Island and Maine, has also been noted.
Formerly known as starfish — a term scientists rejected because they’re more like a sea urchin than a fish — sea stars have been killed by disease several times over the past few decades. But each of those events affected only a single species, marine scientists said, not up to seven, as the new plague has. Divers have previously reported mass sea star deaths in warmer waters south of Santa Barbara, Calif., but not in waters as cool as those of Washington’s Puget Sound.
Scientists disagree slightly on the potential ecological impacts of the current die-off. Sea stars control mussel populations by relentlessly eating them. In their absence, mussels may proliferate and ruin portions of undersea kelp forests that hide small fish from predators and help protect coastal areas from sea surge and storm flooding.
That impact “is very unlikely,” said John Pearse, a professor emeritus of ecology and evolutionary biology at the University of California at Santa Cruz, who believes scientists will figure the problem out before it gets out of control.
But a colleague who is closely studying the disease isn’t so sure. “We are at the onset of the outbreak,” said Pete Raimondi, chair of the Department of Ecology and Evolutionary Biology at Santa Cruz.
More important, said Drew Harvell, a Cornell University professor of ecology and evolutionary biology who studies marine diseases, “these kinds of events are sentinels of change. When you get an event like this, I think everybody will say it’s an extreme event and it’s pretty important to figure out what’s going on.”
Scientists do know that wasting is happening on both coasts, but they don’t know if the two die-offs are linked. They know that tens of thousands of sunflower stars have perished in British Columbia alone since the summer, but they don’t know exactly how many or every place there’s a disease outbreak.
They decline to blame climate change or acidic waters or other warming-related issues, saying that would be just speculation.
Not knowing is scary, Harvell said. If a similar thing were happening to humans, the Centers for Disease Control and Prevention would commit an army of doctors and scientists to unraveling the mystery.
“We have far less resources with ocean organisms to get to the million-dollar question: What is the causative agent?” Harvell said. Is it a bacterium, a virus, a parasite or some disease introduced by an invasive species that plopped out of a ship that had been in foreign waters?
What scientists agree on is that they aren’t close to knowing what’s causing the outbreak, let alone stopping it. Having first detected it this summer, they’ve identified the illness as a wasting disease because sea stars fall apart and waste away, but they really don’t know much else.
“It came from out of nowhere,” said Laura Rogers-Bennett, a senior environmental scientist for the California Fish and Wildlife Service who studies sea stars near San Francisco.
Raimondi started a Web site to track locations where sea stars are turning up dead, inviting anyone who sees one anywhere on the West Coast to report it. “We can build an epidemiological map,” he said. “Here’s where it exists and where it doesn’t exist. You can look for initiation points, causes; if they initiated in warm water, you might have a smoking gun.”
Sea stars have endured localized wasting events in warmer waters, such as in Southern California in 1983 and 1997. But such disease is extremely rare in colder waters, “and that’s a serious concern for us,” Rogers-Bennett said.
Harvell said an event stretching from Southern California to British Columbia with multiple species is virtually unheard of. Pisasters, shaped like stars on the American flag, and vibrant sunflower stars as big as a trash can’s lid, are among the many sea stars affected.
“We collected three different species just from here,” Harvell said, referring to the Atlantic coast, “and five or six species on the West Coast.”
Along with dolphins, whales and sharks, sea stars are, well, stars of the sea. People can wade into the water and pick one up or scuba to greater depths and touch them where they live on reefs. They are harvested — unfortunately, biologists say — to be dried and turned into household decorations.
In British Columbia, Neil McDaniel, a marine naturalist who dives into deep waters to photograph sea stars, said he’s shocked at what’s happening there.
It started in August, when a recreational diver in Howe Sound noticed that sunflower stars — among the world’s biggest, quickest and prettiest — “were kind of dissolving,” McDaniel said. An emergency call to the Vancouver Aquarium brought scientists to the site. What they observed sounded so awful that McDaniel had to see it for himself.
“My dive buddy and I were astonished to see the devastation going on,” McDaniel said. Sunflower stars are usually bright orange and plump, McDaniel said in a telephone interview. But these “looked emaciated. The body walls were rupturing, the internal organs were falling out through ulcerations. It looked like the walking wounded.”
Over the past several years, Howe Sound had become almost overpopulated with sunflower stars, about a dozen per square meter in some areas, McDaniel said. Half the sea stars they saw this summer appeared infected.
When McDaniel returned about a month later, “there was 99 percent mortality. Tens of thousands died in Howe Sound alone in the course of one month,” he said. “These are marvelous animals and such iconic animals, and to see so many of them dying kind of takes your breath away.”
Raimondi has been sending dead sea stars to labs for studies. The bodies might yield an explanation: a communicable disease, a toxin or a parasite. Similar research is happening at the University of Rhode Island.
“We don’t know much yet,” said Marta Gomez-Chiarri, a URI professor and researcher. Although sea star wasting in the Atlantic isn’t new, this episode has been under observation for only two months. “We know it is infectious and that whatever is affecting East Coast species can be transmitted to the West,” she said.
“I’m hoping this is a kind of freakish but natural event, and the sunflower star population will recover,” McDaniel said. “You feel quite helpless. It’s hard to say if things will ever be the same.”