There was once a galaxy of sunflower sea stars in the Salish Sea off the British Columbia and Washington State coasts, but a new study says their near disappearance from the ocean floor should be of special concern.
Researchers at the University of California, Davis, say a wasting disease that affected many star fish from Alaska to Mexico was devastating for the sunflower sea star.
Joseph Gaydos, one of the report's authors and the chief scientist with the SeaDoc Society, said the sunflower that covered the ocean floor in many areas off southern Vancouver Island and Washington state has been virtually wiped out.
"We're really concerned that one could completely disappear," he said in an interview.
The West Coast is renowned for its 28 varieties of sea stars, some not found anywhere else in the world.
In 2013, divers and researchers started noticing the star fish were dying from a disease that experts couldn't figure out.
Three years later, they believe a virus is at fault, but Dr. Gaydos says there may also be other factors, such as water temperature, that makes certain star fish more susceptible.
The study, which was released Wednesday on the online science journal PLOS ONE, says the virus is the largest such disease epidemic affecting multiple species of marine organisms in the world.
Dr. Gaydos said it's like a canine distemper virus that tears through the Serengeti region of Africa, killing everything from lions to jackals.
"There are some diseases out there that affect multiple different species, but we haven't really found one in the marine environment that has had this much impact."
But the die-off of the sunflower, a tire-sized, multilegged, colourful orange or purple star fish, could have other implications, Dr. Gaydos said.
"They're major predators, they eat almost anything they can get a hold of, everything from urchins to mussels, to other sea stars and they'll even scavenge. I saw a picture from a diver where one was eating a bird that had died."
Researchers saw evidence of increases in red and green urchins, which feed on kelp, Dr. Gaydos said.
"Kelp is like a forest, creating a matrix for all the other species to live in, an ecosystem engineer."
He said scientists have been in discussions with the U.S. National Marine Fisheries Service to have the sunflower listed as a species of concern, an informal term referring to a species that may be in need of conservation.
The next step after that is to speak with the Canadian government, he said.
The researchers don't know why the sunflower was especially susceptible to the wasting disease while others, such as the leather sea star, seem to be thriving.
Dr. Gaydos said it could be the species' high volume at the start of the disease that contributed to the die-off.
The sunflowers were once so plentiful in the area they were piled on top of one another and covered entire areas.
"That can contribute to stress. It can also contribute to ease of transmission."