Ed Gullekson / Science Advances
The skin lesions are the first sign that something is wrong. Then limbs fall off and the body disintegrates while it liquefies. What was once a starfish is just a puddle on the ocean floor.
Since 2013, the lavish starfish disease on the Pacific Coast has killed so many starfish that scientists say that this is the largest plague ever observed in the wild marine species. Where there were dozens of stars, divers report that they have not seen any.
And while the epidemic itself is a naturally occurring (though particularly devastating) phenomenon, newly published research indicates that climate change may have exacerbated the lethality of the disease.
"What we're thinking is that the warm water anomalies made these starfish more susceptible to the disease that was already out there," says Joe Gaydos, science director at the University of California, Davis & # 39; SeaDoc Society and an author of a study today in the journal Science Advances .
He and his co-authors analyzed data collected by scuba divers and found that divers would see less living starfish at unusually high water temperatures.
"Thinking that the warmer water temperature itself can cause animals to get sick faster or become more vulnerable is a kind of double blow," says Gaydos. "It's a bit nerve-wracking."
Water surface temperatures have steadily increased worldwide as the Earth warms due to man-made climate change.
The study did not investigate why warmer water could make marine stars more susceptible to disease. The authors hypothesize that the relatively simple immune system of animals may become weaker when starfish become hot.
And the same survey results for divers also confirm an earlier finding: that the mass extinction of starfish causes a cascade of other ecosystem changes. The sea urchins, which eat starfish normally, multiply with abandonment. Whole rocks, once covered with starfish, are now covered in shells.
The Urchins eat seaweed.
"We see these big urn-fish where the urchins ate the whole kelp," says Gaydos. Seaweed forests, like tree forests, are a place where many different species live and feed.
"We have more biodiversity if we have more kelp, so it starts a cascade," he adds. "If you look at land, it would almost be like cutting down a forest."
It is unclear whether the starfish population will recover massively in the coming years. The studies published last year suggest that some starfish may survive the disease and hope that the animals will recover over time.