A Star Is Born … And Then Wastes Away Again
With the second coming of the Blob, sea star wasting disease may make a return.
Early in the summer of 2019, sea stars seemed to be on the mend roughly four years after the initial outbreak of a devastating wasting disease that reduced huge numbers of stars to piles of goo.
“In June and July, it was feeling like a good year,” says Alyssa Gehman, a Hakai postdoctoral researcher at the University of British Columbia. “We were seeing some evidence of recovery.”
Seeing these positive signs, scientists planned a survey trip for the late summer to document the sea stars’ recovery. But when they examined the waters off Calvert Island, on the Central Coast of British Columbia, they encountered disease déjà vu.
One of the hardest hit species in 2015 was the sunflower star, a predatory sea star with up to two dozen limbs that can grow to a meter in diameter. For years after the initial wasting disease outbreak, scientists only found juvenile sunflower stars the size of a salad plate, or smaller.
“This year, we were starting to see 40- to 60-centimeter sunflower stars on occasion,” says Hakai diver Ondine Pontier, who has been part of the team conducting subtidal surveys every year since the outbreak began. “Nothing bigger though.”
While that’s only half the size of the largest sunflower stars, it was still a promising sign that the hard-hit species might be on the road to recovery. Then came the gut punch.
“When we came back in August and early September, we saw what looks like a new wasting outbreak,” Gehman says.
The cause of the wasting syndrome is thought to be a virus, but the exact culprit and how it spreads is still a topic of active research. However, scientists have established a link between a persistent pocket of warm water—nicknamed The Blob—and the initial disease outbreak. Warmer waters exacerbate the disease.
“I came home and saw the tweets from NOAA that the Blob was back,” says Gehman, who added that what the new Blob means for wasting is still unknown. “We were getting hopeful, but the trend isn’t for temperatures to stay down.”
Not all sea star species suffer to the same extent. As populations of one species drop, other less-susceptible species, such as leather stars, can flourish. Leather stars aren’t immune to wasting, but their infection rates are much lower for reasons we don’t quite understand yet. Regardless, losing that many sea stars has a ripple effect through the ecosystem.
The recent prognosis isn’t great, but there are still promising signs that suggest sea stars can be resilient over time. In select areas, divers have begun to notice even larger sunflower stars in pockets of cooler water. Still, with optimism comes the realization that we don’t know what will happen as climate change throws wrench after wrench into our understanding of coastal ecosystems. We’ll be there to find out.