Ochre sea stars have suffered a 95 percent die-off in SLO County

The mass die-off of sea stars along the West Coast continues unabated, including in San Luis Obispo County, where an estimated 95 percent of ochre sea stars have died.

That was the grim news delivered Monday by Pete Raimondi, a marine biologist who is the chairman of the department of ecology and evolutionary biology at the Long Marine Lab of UC Santa Cruz. About 100 people packed the Morro Bay Veterans Hall to hear Raimondi talk about the crisis, known as sea star wasting syndrome.

From Alaska to Mexico, from 70 to 99 percent of sea stars, often called starfish, have died. Areas on the East Coast have also been affected.

The disease was first detected in 2013 and spread rapidly.

“In some places, they are completely gone,” Raimondi said. “It’s bad, and it’s been bad for the past several years.”

Researchers with Raimondi’s lab monitor eight tide pool locations in San Luis Obispo County twice a year, including Shell Beach, Diablo Canyon and Montaña de Oro State Park. About 15 species of sea stars are affected by the disease.

However, the iconic and charismatic ochre sea star has been hardest hit. With their bright orange or purple coloring, ochre sea stars are one of the most recognizable tide pool species.

Researchers believe the disease is caused by a virus that weakens the animals and allows bacterial infections to set in. First, the sea star develops lesions. Then it begins to droop, and its arms fall off.

“It’s super creepy,” Raimondi said. “They can go from healthy to a pile of debris in 24 hours.”

There is no cure for the disease, and scientists can do little but monitor its progress. It is unknown whether the disease is the result of a new virus or whether the sea stars have been weakened by stressors in their environment, such as rising sea temperatures or pollution, making them more vulnerable to the disease, he said.

Rouvaishyana, manager of the Morro Bay Natural History Museum, said few park visitors are aware of the withering syndrome, but State Parks is troubled by it.

“We are concerned with the phenomenon because sea stars are a keystone species for the intertidal area,” he said.

In fact, ochre sea stars were the original keystone species, a wildlife biology concept that states the effect of some species on their ecosystem is vastly disproportionate to their abundance. Sea stars are crucial because they keep mussel and urchin populations in check.

“Mussels take over areas and reduce biodiversity when the stars are eliminated,” Raimondi explained. “We have seen dramatic impacts on kelp forests.”

Raimondi’s researchers have documented places where mussels have taken over some tide pools and forced out other species. Urchins feed on kelp and, without sea stars to keep them in check, they can devastate kelp forests.

The good news is that researchers are finding a lot of baby sea stars in tide pools. Animals like sea stars often react to stress by reproducing as much as possible, he said.

This story was originally published February 15, 2016 at 4:19 PM with the headline "Ochre sea stars have suffered a 95 percent die-off in SLO County."