When Rayna Holtz and Yvonne Kuperberg began monitoring a strip of west-side beach a few years ago, searching for dead sea birds as part of a citizen science project through the University of Washington, they soon realized they likely wouldn’t find any dead birds. So the two women, also Vashon Beach Naturalists, began recording other sea creatures they saw on their monthly walks, thinking it would be interesting to watch how their populations changed over time. Little did they know they would soon see one of the Puget Sound’s most iconic sea creatures — the sea star — nearly disappear from the beach, hit by a mysterious disease that has decimated sea star populations up and down the West Coast.

“I would say the disease hasn’t been abating. It looks to me like it’s raging,” Holtz said last week. Holtz is now one of a handful of islanders collecting data on sea star wasting disease, which came to local waters last year. That information is sent on to scientists, who now believe they are narrowing in on the cause of the gruesome disease. The issue has drawn attention from researchers at the University of California, Santa Cruz, Cornell University, University of Rhode Island, Brown University, Western Washington University and the Seattle Aquarium.

This summer researchers announced they believe the wasting disease — which kills sea stars by causing them to develop lesions, ooze liquid and fall apart — is caused by a virus or bacteria that spreads through the water or through touch. They also believe environmental conditions, likely warm water, may exacerbate the disease.

The disease, which was first spotted about a year ago and was observed on Vashon last winter, has now been spotted as far as north as British Columbia and as far south as Mexico. On Monday it was reported to have infected sea stars in captivation on the Olympic Peninsula.

Holtz says that her and Kuperberg’s beach counts have been somewhat informal, but they believe data from their walks from Sunset Beach to Cove Walk tell a story about Vashon’s experience with sea star wasting disease.

In July of 2010, the women counted 40 sea stars on their walk; in July of 2011 they counted 44; and in July of last year, 40 again. However on their most recent walk, on July 14, the two pored over the beach even more than usual and counted just 16 sea stars, two of which were visibly sick, as well as two dead stars.

“We wondered whether we were going to find any at all. We were really searching,” Holtz said. “That’s probably a much more detailed count than the ones that preceded it.”

Other islanders have reported steep declines in the sea star populations at some of Vashon’s most well-known beaches, with an especially bad die-off in June.

In May, a group of students taking oceanography and environmental science at Vashon High School counted about 800 sea stars at several beaches around Quartermaster Harbor as well as KVI beach, a project funded through a grant from the Washington Environmental Council. They estimated that about 15 percent of the sea stars were infected with the wasting disease, according to Tom DeVries, who recently retired from teaching oceanography at the high school.

Students returned to the same spots in mid-June and found that 60 to 80 percent of the sea stars were gone, DeVries said, and many of the ones that were left were  visibly sick and “at death’s door.” The early summer die-off was also seen at other beaches around Puget Sound, DeVries said, leading some to speculate that warm water could play a role.

“The students were surprised, dismayed and somewhat astounded by the fact that these starfish were disintegrating almost before their eyes, and they hadn’t known about it before we undertook this project,” DeVries said. “To see these starfish infected is pretty depressing.”

Holtz observed the same thing across the harbor in Dockton. After completing a training last winter, Holtz did her first formal sea star count at the Dockton marina, gathering information for the Multi-Agency Rocky Intertidal Network (MARINe), a coalition of research groups collecting sea star survey data. In Feburary Holtz counted two dozen sea stars, only one of which was visibly sick, in a certain part of the marina. She also saw 25 juvenile sea stars clustered together in another area.

“They were all so fat and brilliant. I thought these guys really have resistance,” she said.

However, when Holtz returned to the marina earlier this month, she counted just one juvenile sea star and no adult stars.

“I couldn’t believe my eyes,” she said. “The areas that had not been touched in February have succumbed now.”

One islander has seen the same phenomenon under the water as well. Karlista Rickerson, an avid scuba diver, dives frequently at Tramp Harbor and at the Maury Island Marine Park and estimates she’s seen about 80 percent of the sea stars disappear there. Some from the scuba community have been asked to count sea stars as deep as 120 feet, she said. Unable to dive that deep, Rickerson says she’s watched the disease progress higher up, taking photos and doing her own informal counts.

“There aren’t any to count anymore,” she said last week.

Some islanders, however, report a more hopeful picture. Jeff Adams, a marine water quality specialist with Washington Sea Grant who trained islanders last winter to collect sea star data for MARINe, has been doing his own observations under the north-end ferry dock with beach naturalist Kelly Keenan. The two say that there was a large die-off there as well, but those stars didn’t seem to experience the second wave of die-offs that was seen in other places in June, and in recent months, sea star numbers have held steady. At their last count, they saw 20 or 30 sea stars on six pilings, a number Adams called encouraging.

“The fact that they seem to be hanging in there is encouraging in the least,” he said. “As long as we’ve got some survivors, we’ll start to repopulate.”

Adams, who forwards volunteer data from Vashon and the Kitsap Peninsula on to MARINe, said citizen science has played an important role in the study of sea star wasting disease, as researchers look at why it may affect sea stars in some places  more than others. MARINe has hundreds of survey sites along the West Coast.

“There are only so many researchers, and for issues where volunteers can collect information just as efficiently, it’s a great way to expand the reach,” he said.

While so far just a few Vashon Beach Naturalists have volunteered to look at island beaches, Adams said anyone can get involved. With summer here, he’s also looking to talk with local crabbers. Knowing whether crabbers are still seeing sea stars crawl into their pots could provide a glimpse of how the disease is affecting sea stars in deeper water.

“I’d love to hear from crabbers, if they are catching any,” he said.

Rickerson, the scuba diver, said she wonders how the mass die-off of sea stars may affect the rest of the shoreline ecosystem. Sea stars are considered a critical keystone species, feeding on many other organisms, including barnacles and shellfish, and keeping intertidal communities in balance.

Rickerson also collects and examines water samples for Public Health — Seattle & King County, and she said her most recent sample revealed far less plankton than she normally sees this time of year. She wonders if perhaps there has been a surge in the creatures that feed on the microorganisms — creatures that typically fall prey to sea stars.

“There are too many questions. All I can do is ask more,” she said.

On a sunny day last week, Holtz, a Vashon Beach Naturalists leader who can ramble off the scientific names of different sea stars, paid a visit to the beach near the Cove Motel and examined some large pilings, what would normally be prime habitat for sea stars. She found them mostly covered with mussels and barnacles, with a few purple sea stars near the waterline and one sick sea star tucked inside a hollowed-out area. Walking farther down the beach, however, she was excited to see a cluster of small juvenile sea stars in the bow of an old boat.

Holtz noted that as sea stars weather the disease, she hopes to see more people volunteer  to be eyes on the beach.

“I think that on the one side it’s scary because you don’t know if they’re going to rebound. But on the other hand, it’s a rare opportunity to see the impact of a keystone species, to see what it really means,” she said. “I think it’s very important not to miss this chance to learn whatever we are going to learn from it.”

For information on collecting sea star data for MARINe, contact Jeff Adams at jaws@uw.edu or (360) 337-4619.