Marine biologists aren't quite sure what is causing the recent string of sea star deaths along the US's west coast. The symptoms include white lesions that deteriorate their arms and eventually infect the core body, the AFP reported.
Most believe they're first contracting a pathogen (either a virus, bacteria, or parasite), leaving them vulnerable to infection, at which point a second bacteria causes the more dramatic symptoms that lead to their death.
"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 University of California, Santa Cruz, told AFP.
First observed in 2013, the infection has a 95 percent mortality rate and has wiped out entire populations, which was the case in the Washington State's Puget Sound as well as on several locations along California's coast and the coast of British Canada. The two species most affected are Pisaster ochraceus (purple sea star or ochre starfish) and Pycnopodia helianthoides (sunflower sea star).
Smaller sea star epidemics have occurred over the last twenty or so years, most recently along the East Coast last year. That decline was also associated with a pathogen, though previous fall-offs were associated with warmer waters, according to the AFP.
Like most of the ocean's creatures, sea stars are an important member of the ecosystem. They "eat mussels, barnacles, snails, mollusks and other smaller sea life, so their health is considered a measure of marine life on the whole in a given area," according to the AFP.
