A deadly virus caused a massive starfish die-off along North America's Pacific coast beginning in 2013. Between 2014 and 2015, the "sea star wasting disease" had killed millions of starfish, decimating between 80 and 99 percent of purple sea stars (Pisaster ochraceus) and affecting about 40 other sea star species.
Researchers who have been monitoring sea stars, however, reported that after being hit by the most severe marine ecosystem epidemic, sea stars appear to make a comeback.
A large number of baby starfish has been observed in the past several months off the coast of Oregon two years after the disease nearly wiped out the population of the animals.
"Although historically P. ochraceus recruitment has been low, from fall 2014 to spring 2015 an unprecedented surge of sea star recruitment occurred at all sites, ranging from ~7x to 300x greater than in 2014," the researchers wrote in their study, which was published in the journal PLOS ONE on May 4.
The researchers, however, warned that while the appearance of these juveniles offers some hope for sea star populations, it does not mean that the threat of the disease is over. Another round of the disease may prove disastrous.
Study lead author Bruce Menge likewise said that the surge in juvenile starfish populations does not mean that more of the marine creatures are being born.
"It wasn't a case of high settlement, or more sea stars being born. They just had an extraordinary survival rate into the juvenile stage," said Menge, a professor of marine biology at Oregon State University. "Whether they can make it into adulthood and replenish the population without succumbing to sea star wasting disease is the big question."
The sea star wasting disease is characterized by the emergence of lesions, followed by body fragmentation that eventually leads to the death of the affected animal.
The wasting is believed to be caused by the sea star-associated densovirus, albeit there may be other still unidentified factors that triggered the epidemic, which is feared to potentially affect the biodiversity in starfish habitats.
Some researchers attributed the outbreak to warmer waters caused by global warming but research conducted by Menge's team did not find an association between water temperatures and the outbreak.