A marine epidemic that has killed over 20 different species of sea stars from Alaska to Mexico — the largest ever documented — has been happening over the past decade. Scientists have long sought the culprit and have finally identified it, according to a new study in Nature Ecology & Evolution.
The identified strain of Vibrio — the same bacterial genus that can cause cholera — has infected the sunflower sea star. The strain, V. pectenicida, can cause exterior lesions and melt the sea stars’ tissues over a two-week process that eventually kills them.
“Understanding what led to the loss of the sunflower sea star is a key step in recovering this species and all the benefits that kelp forest ecosystems provide,” said Jono Wilson, the director of ocean science for The Nature Conservancy’s California chapter, in a press release.
The Sea Star Wasting Disease
In the past decade, the disease known as the sea star wasting disease (SSWD) has wiped out over 90 percent of sunflower sea stars. These sea stars can sprout 24 arms and can grow up to the size of a bicycle tire, and they also support kelp forests.
“When we lose billions of sea stars, that really shifts the ecological dynamics,” said Melanie Prentice, the first author on the study and an evolutionary ecologist at the Hakai Institute and UBC, in the release.
“In the absence of sunflower stars, sea urchin populations increase, which means the loss of kelp forests, and that has broad implications for all the other marine species and humans that rely on them. So losing a sea star goes far beyond the loss of that single species,” added Prentice.
Read More: Spiky, Star-Shaped Creatures Show the Deep Sea Is a “Connected Superhighway”
Diagnosing Sick Sea Stars
Because sea stars lose their arms and show similar signs of contortion from other stressors and diseases, the researchers needed to identify the disease from a known pathogen. They first ruled out viruses, and it wasn’t until the team used microbial analysis to examine the blood of the sea stars that they found V. pectenicida.
“When we looked at the coelomic fluid between exposed and healthy sea stars, there was basically one thing different: Vibrio,” said Alyssa Gehman, senior author of the study and a marine disease ecologist at the Hakai Institute and UBC, in the release. “We all had chills. We thought, That’s it. We have it. That’s what causes wasting.”
The research was a four-year process, supported by The Nature Conservancy, the Tula Foundation, UBC, and other institutions, according to the release.
Recovering Marine Life
Now that the pathogen has been identified, researchers can focus on the resilience of the disease and what drives it. Rising ocean temperatures could be increasing the disease since Vibrio is known to reproduce rapidly in warm water, according to Gehman.
The culprit is now known, and researchers hope that this will help recovery efforts for these marine ecosystems.
“This finding opens up exciting avenues to pursue and expands the network of researchers able to develop solutions for recovery of the species,” said Wilson in the press release. “We are now actively pursuing studies looking at genetic associations with disease resistance, captive breeding of the animals, and experimental outplanting to understand the most effective strategies and locations to reintroduce sunflower sea stars into the wild.”
Read More: Discover How Starfish Gained Five Arms After Evolving From 500-Million-Year-Old Ancestor
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