Millions of Starfish Are Literally Ripping Themselves Apart, and Climate Change May Be to Blame

Millions of starfish along the west coast of North America are dying in a particularly gruesome way: self-inflicted dismemberment. The mysterious “sea star wasting syndrome” is a nightmarish infection that has completely baffled biologists. “There were just bodies everywhere, and they were just like splats,” scuba diver Laura James told PBS. “To me, it always looked like somebody had taken a laser gun and just zapped them and they just vaporized.”

The first symptoms of these “wasting events” are white lesions that form in the starfish's appendages, weakening the surrounding tissues. This bodily deterioration causes the animals to suffer grotesque contortions, and eventually the limbs of the afflicted star pull away from the body, break off, and abandon the central disk with its insides hanging out. Normally, starfish can regenerate severed body parts, but those that are infected are unable to do so, and they typically die quickly. The mortality rate for this disease is 95%.

The cause of the disease is complex, but so far, it's thought to be a deadly cocktail of bacteria, virus, and climate change.

The outbreak, which was first noticed in June 2013, has spread to at least 12 species of Pacific sea star. It has been particularly devastating for two starfish species. One, the Pycnopodia helianthoides (also known as the sunflower sea star), is the largest and heaviest sea star in the world, growing to an average of 80 centimeters in diameter and 5 kilograms in weight.

The other Pisaster ochraceus (commonly known as either the purple sea star or ochre starfish) will be familiar to anyone who has visited the Pacific Northwest, where great numbers hang out in tide pools and rocky shores. It is a keystone species, meaning that purple sea stars have a disproportionate effect on their environment relative to their abundance. In other words, the health of their population is a litmus test for the ecosystem as a whole. This certainly amplifies concerns over these wasting events, and their potential to dramatically offset biodiversity in starfish habitats.

The syndrome is not well understood, but biologists are genetically sequencing specimens to see if they can locate the anomaly. Researchers are also encouraging a “citizen science” approach to help acquire data on the outbreak. So, if you happen to be snorkeling on the West Coast, and see a starfish suffering from the disease, or already torn apart by it, tweet a photo of it with the hashtag “sickstarfish.” Not only will this give scientists idea of how far the outbreak has advanced, it will help spread the word among the public that starfish are self-destructing on a massive scale.

So far, the best guess as to the mechanism behind the disease lives up to its gory prognosis. Biologists think it may be a one-two punch administered by both viruses and bacteria. “What we currently think is likely happening is that there is a pathogen, like a parasite or a virus or a bacteria, that is infecting the sea stars and that compromises in some way their immune system,” Pete Raimondi, chair of the Department of Ecology and Evolutionary Biology at the UCSC, told the AFP.

A sunflower sea star eating a freaking jellyfish. Photo via Andrew Cauthen/d pics.

It's also worth noting that this is not the first outbreak of sea star wasting syndrome ever observed, nor is the infection limited to the east Pacific. In 1972, large numbers of Asterias vulgaris, a starfish common in the northeast Atlantic, died off after displaying the same gory symptoms. There were also epidemics in 1978 and 1982.

Though the evidence is still speculative, there's good reason to believe that climate change is a major culprit in the propagation of the disease. The only consistent link between the outbreaks is that they were all preceded by above-average water temperatures. This is somewhat ironic since starfish have been touted as being among the most likely marine animals to survive the effects of global warming. Their calcified exteriors are very resistant to ocean acidification and, as their impressive global range demonstrates, they are incredibly adaptable.

But even these durable echinoderms have vulnerabilities. We may soon be adding millions of torn-up starfish corpses to the pile of calamities caused by climate change.