The deadly sea star disease, which causes sea stars to melt into a puddle of slime, is not as a result of an infection, but the result of multiple types of bacteria living within millimeters of the sea stars.
They act by depleting the oxygen from water, which in turn suffocates the animals. The bacteria thrive in areas of high levels of organic matter in warm water.
The disease led to the death of hundreds of sea stars
The disease first came to public attention in 2013 when sea stars living off the U.S. Pacific Coast died in massive numbers. Outbreaks of the disease had also occurred before 2013, but never at such a large scale.
Sea star wasting disease has lethal symptoms like decaying tissue and loss of limbs, which eventually leads to the death of the animal.
Scientists initially suspected that a virus or bacterium might be the culprit, but their hypothesis was abandoned when subsequent studies found no relationship between the virus and dying sea stars.
New findings show that a disease can be caused by a group of virus or bacteria
The new finding that a group of nutrient-loving bacteria can drain oxygen from the water and cause wasting disease “challenges us to think that there might not always be a single pathogen or a smoking gun. Such a complex environmental scenario for killing sea stars is a new kind of idea for [disease] transmission.” says Melissa Pespeni, a biologist at the University of Vermont.
Ian Hewson, a marine biologist at Cornell University, says different ideas were tested to find the cause of the sea-wasting disease. He and colleagues analyzed differences in water temperature to exposing the animals to bacteria.
Their breakthrough came when the researchers examined the types of bacteria living with healthy sea stars and compared them with those living among the animals with wasting disease.
“That was when we had our aha moment,” says Hewson.