On a windless, cloudless night in late January, Salish Sea ecologist Russel Barsh and his team of scientists at the Kwiáht biology lab scoured Indian Island for sea stars. No humans live on what is technically the island, a tiny bit of rock just south of Eastsound on Orcas Island, but the winter low tide reveals a colorful variety of the island’s other inhabitants: violently mating sea slugs, dazzling red octopuses, reptilian-looking snail fish, and the island’s famous sea stars—one as big as a yard wide—that have traditionally feasted on the mussels and clams hidden in the sand.

Indian Island’s sea star population—like other sea star hangouts up and down the West Coast—experienced a swift and mystifying die-off that inspired alarmist headlines in 2014. Marine biologists looked on with horror as appendages of the keystone species—a species that plays a fundamental role in its ecosystem—washed ashore. But this year, Barsh and his crew found something hopeful: hundreds of sea stars, babies, mostly. And healthy, from the looks of it.

The discovery, which other sea star monitoring sites have also documented, is a big deal. Barsh and his colleagues, a scrappy team of conservationists who have been hyper-focused on Salish Sea ecology since 2006, were specifically looking to see whether Indian Island’s sea star population would make a comeback. To some extent, it did.

“At this point, at worst we’re at less than 1 percent morbidity, no bits and pieces [of sea stars] like we saw last summer,” Barsh told me after the January survey. “Now the question is how many of the little guys we’re seeing will be lost to predation and disease this year.”

Barsh has reason to be cautiously optimistic, or optimistically cautious. Other monitoring sites have picked up on the explosion of new, healthy-appearing babies and the absence of adults. But just because the babies look healthy now doesn’t mean that they won’t get sick. And just because there are lots of them at present doesn’t mean they’ll survive into adulthood.

“The real question is: Will that class of babies correspond to adults in the future?” asked Peter Raimondi, sea star researcher and chair of the department of ecology and evolutionary biology at the University of California-Santa Cruz. “It’s certainly a good sign." But, he said, expectations will be tempered if more babies than usual end up dying prematurely. "We’re not sure that the disease is gone," he noted.

That’s the other mystery afoot. Despite a major report identifying a possible culprit of sea star wasting disease late last year, scientists still don’t really know what caused the sea star deaths. In November, a national research team (including Raimondi) published a study showing that sick sea stars carried something called a densovirus, a malady typically found in arthropods (like insects and crustaceans). The researchers found that viral tissue from sick sea stars injected into healthy ones got the healthy ones sick. At the same time, they also discovered that the virus has existed in what were thought to be healthy sea stars going as as far back as 1923.

If a long-existing virus did cause the die-off, was its outsize mortality rate exacerbated by other causes, like warming ocean temperatures and other stressful conditions? Some scientists suggest that the virus may have struck sea stars whose immune systems were already compromised, like the way pneumonia might do more harm to human beings with AIDS. But that doesn’t rule out the other possibilities. Was last year’s bout of sea star wasting a freaky way that nature automatically controls an overburdened sea star population? Or did humans (once again) cause something troubling and irreversible in an animal species?

Barsh doesn't trust the big, bad virus explanation alone. “The issue isn’t that we have superbugs; the issue is that we’re weakening ecosystems’ ability to adapt to new pathogens,” he said. “[With] chemical insults and new molecules that fool animals’ endocrine systems, there’s a fair chance that we’re just tuning down everything’s immune system, and then you see huge die-offs of organisms, because the immune response of every animal affected is so degraded.”

“It wasn’t absolutely clear that [the densovirus] was causing it,” Raimondi, the UCSC researcher, explained. “Even if it was a densovirus, it doesn’t mean that there wasn’t something in the environment that caused individuals to be susceptible.”

Ian Hewson, a Cornell University ocean microbiologist and lead author on the densovirus study, isn’t ruling out environmental causes, either. “Certainly the oceans are warming and acidifying, no question about it,” Hewson said. But there’s not a clear correlation between sea star wasting and warming temperatures, he added—even though warmer temperatures make sea stars more stressed out. Researchers haven’t yet looked into how ocean acidification could affect sea stars’ susceptibility to the virus, and it’s difficult to replicate conditions that would stress out sea stars in a lab.

“We’re calling it one disease, but it’s probably a set of symptoms that can be linked to many things,” Hewson said. “I’m not discounting the possibility that there’s some unmeasured environmental factor in this disease.”

It’s likely sea stars will recover from this last bout of sea star wasting, Raimondi added. But scientists still need to figure out whether humans played a role in the startling die-off. Otherwise, it could happen again, and sea stars might not bounce back.

In response to the ongoing concern, last week Congressman Denny Heck (D-WA) introduced legislation that would fire off a 120-day emergency research protocol to stop sea star wasting disease—or other marine diseases like it—from spreading.

“Starfish are a keystone species, meaning their decline will hit the ecosystem and economy hard if something isn’t done soon,” Heck said in a statement. “The Marine Disease Emergency Act will work to save our delicate ecosystem and prevent the inevitable backlash for our marine environment and fishing industries.”

An emergency action plan sounds like a good idea. Then again, Barsh points out that the lack of longitudinal—or long-term—research on sea star communities is one of the reasons why sea stars’ mass disappearance is so poorly understood. Hit-and-run studies don’t do much to explain why sea stars are getting sick in certain places and not others. That’s also one of the reasons why Barsh and his research team at Kwiáht are wholly dedicated to sticking it out on islands in the Salish Sea.

“Sometimes it takes a long time to figure something out to the point where you’re right,” Barsh said.

This article has been updated since its original publication.