VANCOUVER - Last month, a diver alerted Vancouver Aquarium staff that he had found a number of dead and decaying sunflower sea stars in the cold Pacific waters of a popular dive spot just off the shore of West Vancouver.
Within weeks, the tentacled orange sea stars had all but disappeared in Howe Sound and Vancouver Harbour, disintegrating where they sat on the ocean floor.
And aquarium staff don't know just how far-reaching the "alarming" epidemic has been, and whether this and other sea star species will recover.
"They're gone. It's amazing," said Donna Gibbs, a research diver and taxonomist on the aquarium's Howe Sound Research and Conservation group.
"Whatever hit them, it was like wildfire and just wiped them out."
The sunflower sea star population had inexplicably exploded in recent years. In some areas they were stacked several stars deep, and those conditions may have been ripe for disease, she said.
"We are seeing some babies, so we're wondering if they will survive," Gibbs said. "We're hoping we get the natural abundance back without this overabundance."
Other species of sea star — commonly called starfish — are also affected.
Jeff Marliave, the aquarium's vice-president of marine science, said the collapse has been confirmed around the Defence Islands, north of Vancouver, and off the south shore of Bowen Island, where there is no longer any evidence of what was a huge overpopulation of the voracious cousins of the sea urchin.
"Where the population density had been highest in summer of 2012, on the western shore of Hutt Island, all the sunflower sea stars are gone from that area, with rivers of ossicles (a hard body part) filling ledges and crevices," Marliave wrote in his blog.
The aquarium has dubbed the epidemic Sea Star Wasting Syndrome.
Aquarium staff don't know the cause because they have had trouble gathering specimens for testing, as starfish that looked healthy in the ocean turned up as goo at the lab.
The epidemic has killed thousands of the marine invertebrates, which can weigh up to five kilograms and live from three to five years.
The Howe Sound research team has heard from veterinarians and other marine experts that similar die-offs have taken place in Florida and California.
"We're just not sure yet if it's all the same thing," Gibbs said. "They're dying so fast."
In July, researchers at the University of Rhode Island reported that sea stars were dying in a similar way from New Jersey to Maine, and the university was working with colleagues at Brown and Roger Williams universities to figure out the cause.
The collaboration came about after a graduate student collected starfish for a research project and then watched as they "appeared to melt" in her tank.
Like Howe Sound, the Narragansett Bay area where those starfish were collected had seen an explosion in the population in the previous few years.
"Often when you have a population explosion of any species you end up with a disease outbreak," Rhode Island Prof. Marta Gomez-Chiarri said in a statement at the time.
"When there's not enough food for them all it causes stress, and the density of the animals leads to increase disease transmission."
Unfortunately, once that disease is in the environment, it can be difficult to get the population back, she said.
"Diseases don't just completely disappear after a massive die-off."
Vancouver Aquarium staff are asking divers and other members of the public to help monitor the spread of the disease, and report any similar sun star deaths to firstname.lastname@example.org.
Note to readers: This is a corrected story. An earlier version said sea stars live up to 35 years.
Also on HuffPost:
Carnivorous Jellyfish (Athorybia rosacea)
Sea Cucumber (Enypniastes)
Dumbo Octopus (Grimpoteuthis)
Siphonophore (Physophora hydrostatica)
Galatheid Crabs (Munida quadrispina)
Vent Shrimp (Rimicaris exoculata)
Black Dragonfish (Idiacanthus atlanticus)
Dinoflagellates (Pyrocystis fusiformis)
Purple Sea Pen (Virgularia sp.)
Blobfish (Psychrolutes marcidus)
Giant Squid (Architeuthis)
Giant Isopod (Bathynomus)
Anglerfish ((Melanocetus johnsoni)
Fangtooth Fish (Anoplogaster brachycera)
Basket Star (Euryalina)
Malagasy Cave Fish (Typhleotris pauliani)
Glass Squid (Cranchiidae)
Flashlight Fish (Anomalops katoptron)
Squidworm (Teuthidodrilus samae)
Comb Jelly (Lampea pancerina)
Pancake Batfish (Halieutichthys intermedius)
NEXT: <a href="ir=Canada%20British%20Columbia" target="_blank">Amazing Sea Creatures</a>
A red lionfish (Pterois volitans) swims in the aquarium of the Schonbrunn zoo in the gardens of the Schoenbrunn Palace in Vienna on October 16, 2012. The red lionfish is a venomous coral reef fish. ALEXANDER KLEIN/AFP/Getty Images
A California sea lion and a walrus kiss each other during a show at the Hakkeijima Sea Paradise aquarium-amusement park complex in Yokohama, southwest of Tokyo, Sunday, Sept. 16, 2012. (AP Photo/Itsuo Inouye)
A two-day-old female white whale swims with her mother at the Hakkeijima Sea Paradise aquarium-amusement park complex in Yokohama, southwest of Tokyo, Saturday, June 30, 2012.(AP Photo/Itsuo Inouye)
A seahorse swims in an aquarium in the zoo of Frankfurt, Germany, Tuesday, Oct. 16, 2012.(AP Photo/Michael Probst)
A Cownose Ray swims in a tank during a preview of the newly renovated Suzanne and Walter Scott Aquarium at Henry Doorly Zoo in Omaha, Neb., Wednesday, April 4, 2012.The aquarium opens to the general public on Thursday, April 5. (AP Photo/Nati Harnik)
King penguins stand in an enclosure at the Hakkeijima Sea Paradise aquarium-amusement park complex in Yokohama, near Tokyo, Sunday, Sept. 30, 2012.(AP Photo/Itsuo Inouye)
In this photo taken Thursday Aug. 2, 2012 and released by the Monterey Bay Aquarium, a male weedy sea dragon at the Monterey Bay Aquarium swims with some of his newly hatched babies on in a sea dragon display thats part of the aquariums special exhibition, The Secret Lives of Seahorses. in Monterey, Calif. The inch-long fish, Australian relatives of the seahorse, were carried as eggs on a brood pouch under the father sea dragons tail. (AP Photo/Monterey Bay Aquarium, Randy Wilder)
Activists from environment campaign group Greenpeace wearing cardboard tuna cutouts hold a protest in front of South Korea's embassy in Manila on November 29, 2012. The activists sought conservation commitments from the fishing powers in the upcoming global summit on Pacific tuna fisheries to be hosted by the Philippines next week. NOEL CELIS/AFP/Getty Images
This Sept. 5, 2012 photo shows Serena, a dugong at the Toba Aquarium in Toba, Japan. Dugongs, a sea mammal related to the manatee, are rare in captivity. The aquarium gift shop sells stuffed dugongs and dugong cookies. (AP Photo/Linda Lombardi)
This May 9, 2012 photo provided by the New England Aquarium in Boston shows a rare calico lobster that could be a 1-in-30 million, according to experts. The lobster, discovered by Jasper Whites Summer Shack and caught off Winter Harbor, Maine, is being held at the New England Aquarium for the Biomes Marine Biology Center in Rhode Island. The lobster is dark with bright orange and yellow spots. (AP Photo/New England Aquarium, Tony LaCasse)
Pterophyllum scalare fish are displayed at the 2012 Taiwan International Aquarium Expo in Taipei on November 9, 2012. More than one hundred fish tanks from many countries will be on display in the four day exhibition at Nangang Exhibition Hall from November 9 to 12. Mandy Cheng/AFP/Getty Images
In this Oct. 15, 2012 photo provided by the Wildlife Conservation Society, Mitik, an orphaned Pacific walrus calf rescued off the coast of Alaska, emerges from his tank at the New York Aquarium in the Brooklyn borough of New York. Mitik suffered from a number of ailments when he was rescued in July but is making progress as he receives round-the-clock care at the aquarium. (AP Photo/Wildlife Conservation Society, Julie Larsen Maher)
Phenacogrammus interruptus fish are displayed at the 2012 Taiwan International Aquarium Expo in Taipei on November 9, 2012. More than one hundred fish tanks from many countries will be on display in the four day exhibition at Nangang Exhibition Hall from November 9 to 12. Mandy Cheng/AFP/Getty Images
This photo taken July 4, 2012, at the Alaska SeaLife Center in Seward, Alaska, shows a baby beluga calf being rehabilitated at the center. The whale was approximately two days old when it was found in Bristol Bay, Alaska, and separated from its mother. Staff from the Alaska SeaLife Center is receiving help with the whale's care from the Georgia Aquarium in Atlanta, Shedd Aquarium in ChiCago and SeaWord in San Diego.. (AP Photo/Mark Thiessen)
A Pacific white-sided dolphin calf swims along with its mother Piquet, Tuesday, June 12, 2012, at Chicago's Shedd Aquarium. The baby male dolphin, which does not have a name, was born on Memorial Day. (AP Photo/Kiichiro Sato)
A seahorse (Hippocampus Reidi) is displayed during a news conference before the 2012 Taiwan International Aquarium Expo in Taipei November 5, 2012. More then one hundred tanks of fish from many countries will be on display in the four day exhibition at Nangang Exhibition Hall from November 9 to 12. Mandy Cheng/AFP/Getty Images
A still unnamed King penguin chick that hatched on April 9 is unveiled at The Aquarium at Moody Gardens, Monday, April 23, 2012, in Galveston, Texas. A blood test will be conducted to determine the gender of the bird who came into life weighing about 20 ounces. This chick is the 14th King penguin chick to have been successfully bred at the aquarium. Due to space limitations, this chick will be go to another facility once weaned from its parents. The chick currently is in the main penguin exhibit at the aquarium which also home to Gentoo, Macaroni, Rockhopper and Chinstrap penguins. (AP Photo/Houston Chronicle, Johnny Hanson)
A Rock Beauty angelfish looks out from its tank at the Greater Cleveland Aquarium in Cleveland Wednesday, Jan. 18, 2012. Developed by Marinescape NZ Limited, Ohio's only free-standing aquarium opens Thursday with two preview days for annual pass holders and opens to the public Saturday, Jan. 21. (AP Photo/Mark Duncan)
This image provided by the Cabrillo Marine Aquarium shows a female Argonaut, or paper nautilus, a species of cephalopod that was recently scooped out of the ocean off the California coast. The baseball-sized animal is making herself at home at the aquarium, bobbing up and down in her tank furling and unfurling her sucker-covered arms. This strange octopus is rare in California, because it only lives in tropical and subtropical waters. (AP Photo/Cabrillo Marine Aquarium, Gary Florin)