Bacteria Kills Hundreds of Starfish
A marine biologist at the University of British Columbia, Christopher Harley was examining the tide pools on a shoreline on Vancouver Island in 2014 when he saw many starfish with their arms either twisted, missing, or dead.
Not long ago, he said that one of his favorite parts of the ecosystem, the “supremely weird” sea stars are “dissolving away.”
An outbreak of starfish wasting disease in 2013 has spread through the Pacific Coast of North America, causing billions of starfish to crumple and disintegrate. And over the last decade, Sunflower starfish, the world’s largest starfish lost 90 percent of its population. Because sea urchins are normally preyed on by starfish, their population grew by a lot and ended up wiping out entire kelp forests.
Unfortunately, the disease killed 20 star fish species throughout the Pacific Coast. Many efforts have been taken to try and bring back these species. The Nature Conservancy led a recovery program for the Sunflower starfish species is trying to bring back the animal to its natural habitat, and dozens of aquariums have been working together to captive-breed them. Experts say that it should be easier, now that we know the cause.
Although the cause of the disease has remained unknown—on Monday, a recent study showed that the killer is a bacteria called the Vibrio pectenicida.
Dr. Harley, who was not part of the research, but was waiting for an answer for over a decade stated, “I have been waiting for this for a long time.”
A marine ecologist at the Hakai Institute in British Columbia, Alyssa-Lois Gehman led a team of scientists and ran many experiments over a course of four years to find the cause. They published what they had found in Nature Ecology and Evolution which helped find cures for the starfish which would’ve not possible without knowing the cause of the disease.
During the study, Dr. Gehman and her team of scientists quarantined animals and if they got sick, they would put them with healthy starfish to see if those would get sick too. The newly infected starfish would become the starting points for the researchers. The researchers would take sample of coelomic fluid from the animals’ bodies and put it in healthy star fish. Ceolomic fluid is the blood of starfish which carries the nutrients.
Focusing on coelomic fluid and not on tissue samples was a “big breakthrough,” according to a disease ecologist at the University of Washington, Drew Harvell, also a part of the research team.
Researchers heated samples of the coelomic fluid to kill whatever might be in it, and injected it into other healthy starfish. Dr. Gehman said that none of the starfish injected with heat-treated fluid died or even lost an arm. On the other hand, about 90 to 100 percent of starfish that did not get the fluid ended up dying.
They examined the healthy and unhealthy starfish, and realized Vibrio pectenicida was only in the unhealthy starfish. They then isolated the bacteria and grew it in the lab, then tested it in the field and confirmed that it was the one harming starfish.
Dr. Gehman said, ‘To have one pathogen, V. pec, stand out so clearly as causing the disease was surprising and exciting.”
An evolutionary ecologist and geneticist at the Sunflower Star Laboratory in Moss Landing, California, Lauren Schiebelhut said there are two ways to help the starfish recover. One included choosing starfish that show the most resistance to the bacteria. The second way is to give them probiotics that have other microorganisms that might help them face the pathogens. This technique has worked with coral reefs.
Dr. Schiebelhut stated, “Those are just a few of the things that opened the door that we couldn’t do.”
There are many questions that still are unanswered. How does the bacteria travel to one starfish to another? Is the bacteria introduced to North American coasts or was it native? Is it increasing in the food of the starfish?
An ecologist at the U.S. Geological Survey, Kevin Lafferty asked, “Where did it come from?” He also added that if it was introduced through aquaculture, researchers could stop future spreads from happening.
Dr. Lafferty said that when this disease hit California in 2013, it had felt like a starfish apocalypse. He remembered snorkeling in kelp forests and seeing many sea stars melting, twisted, or simply just piles of skeletons.
“Maybe these are the lucky ones from the old saying, ‘Thank your lucky stars,’” he said.
Dr. Harvell said the finding was “incredibly fulfilling and important” after so many years of hard work. He added, “For me, it’s the discovery of the decade.”
