A Boom in Starfish Babies Is a Good Sign After the Chaos of Melting Disease

In 2013 and 2014, a shocking number of starfish died along the Pacific coast, their bodies melting away from a mysterious wasting disease. Now, a glimmer of hope has emerged: it looks like the number of young starfish is rebounding on the Oregon coast, according to a new report from researchers at Oregon State University. They're hoping these will translate into more healthy adult starfish, but it's still no guarantee that the starfish plague is over.

From Alaska to Baja California, starfish (also called sea stars, because they aren't technically fish) have been ravaged by what could be a virus. During the worst of outbreak, marine biologists saw them sprout lesions and pull apart or disintegrate, a horrible way to go.

Motherboard reached out to Bruce Menge, professor in the Department of Integrative Biology at Oregon State University, who led the study. He explained that the number of baby starfish, also called recruits, seems to be climbing. In fact, despite the wasting disease that had been going around in the spring of 2015, there were weirdly more baby starfish in the water than ever.

"The numbers of recruits was unprecedented in my decades-long career studying this system," said Menge in an email. "Numbers were up to 300 times that we quantified in the previous 15 years, and qualitatively, far higher than I've ever seen dating back to at least the early 1980s."

According to Menge, similar results were found in coastal waters in northern and central California. The surprising bump in the number of baby recruits might be a result of more food being available, as there were fewer adult starfish around competing for prey like immature mussels. But we still can't say for sure if this encouraging number of babies means they're all recovering.

"The uncertainty in the large number of recruits out there is whether or not they'll survive to adulthood," said Menge. "The disease is still happening, though not at the epidemic level that it was." Baby starfish are vulnerable to the disease, too. "So, cautious optimism is the word."

In 2013, BC saw up to 90 per cent of its sunflower star populations demolished by the same wasting disease. Researchers there still have reason to worry. Along Canada's west coast, the numbers of young starfish are rebounding, but that doesn't mean they'll survive into adulthood. And that has far-reaching and disastrous consequences for the entire ecosystem.

"In the two years following the mass mortality of sea stars around Vancouver, we've seen lots of juvenile sunflower stars, but by spring, they were gone," said Isabelle Côté, professor of marine ecology at Simon Fraser University, in an email. "The same thing is happening on the west coast of Vancouver Island."

Jessica Schultz, a grad student at Simon Fraser working with the Vancouver Aquarium, released a recent report that shows how the loss of sea stars could trigger what's known as a trophic cascade. These occur when the high-tier predator is removed from an environment.

Even with the loss of one predator, lower rungs of the food chain begin to overpopulate­—causing the delicate ecological balance to be thrown out of whack.

According to Schultz's survey, the populations of the sunflower sea star, a common species in Howe Sound, disappeared so quickly in 2013 that the researchers were unable to determine where the disease happened first, as they all seemed to succumb at once. "It is still very rare to encounter a sunflower star of more than about 20 cm diameter [in Howe Sound]," said Côté, who was part of the team who helped Schulz. Before the outbreak, "the largest were up to nearly 100 cm."

There were also way more green urchins around—four times the normal number—which is a common prey of the sunflower star, they said, and shrinking kelp coverage (food for the green urchins) in many of the sites they sampled along the BC coast.

West coast starfish, and other creatures in their food web, aren't out of the woods yet.