5.7B sunflower sea stars have died in past decade, bringing species to brink of extinction

New research shows that more than 90 per cent of sunflower sea stars off the West Coast have died over the past decade, and the species is close to extinction. 

The study, led by Oregon State University, the Nature Conservancy and over 60 partner institutions led by the International Union for Conservation of Nature, estimates that as many as 5.75 billion sunflower sea stars have died since 2013. The loss represents a 90.5 per cent decline.

Alyssa Gehman, a postdoctoral researcher at the Hakai Institute and the University of British Columbia (both partner institutions on the study), says the die-out has put the sunflower sea star on the critically endangered list — one step away from extinction. 

Gehman says it’s a devastating loss.

“They’re gorgeous stars. They’re really charismatic. They’re large. So if you think about the size of a Frisbee, they’re actually four times that size,” Gehman said. “They’re voracious predators.”

The sea stars — also called starfish — which are brightly coloured orange or purple and have as many as 20 to 30 arms, were commonly found along the West Coast from Mexico to Alaska. 

“There are many of them here on the British Columbia coast — or there were,” she said.

The decline in the population is partly due to an outbreak of sea star wasting syndrome, a disease that starts with lesions, little white spots on the skin, and eventually causes the sea star to dissolve.

Healthy, multi-armed sunflower sea stars are renowned predators, but this Howe Sound specimen appears to be dying from sea star wasting disease. (Donna Gibbs/Vancouver Aquarium in Schultz et al. 2016)

While researchers are still trying to figure out the exact cause of the disease, warming waters have exacerbated it. 

“The disease spread is associated with the anomalously warm water. So the marine heat waves that you probably have heard about in the Pacific … caused the disease to move faster within the sea stars and potentially also transmit faster between stars,” she said.

Subsequent effects of decline

Sunflower sea stars are a key predator of sea urchins. With the loss of the sea star population, the sea urchin population has exploded which, in turn, has led to the decline of many marine kelp forest environments.

“These are just beautiful ecosystems or critical habitats for multiple organisms and they support multiple fisheries,” she said. 

Kelp forests provide habitat for a whole ecosystem of animals in the ocean, so the loss of kelp can have cascading implications for other creatures. (Monteray Bay Aquarium)

Unfortunately, Gehman says, there’s little chance of recovery for the sunflower sea star population as it stands. The increasingly rare sea stars were last seen in Mexico in 2016, in California in 2018, and only in a handful of cases in the outer coasts of Oregon and Washington in 2018.

Researchers are now focusing their efforts on a few remnant populations in B.C. and Alaska to understand why they have survived.

“[These populations] are going to be incredibly important to our ability to respond to this devastating loss,” she said.

Gehman says they are soliciting help from the public in locating these populations. If you are out and see a sea star, you can take a picture and upload it to seastarwasting.org 

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