A bacterial species has been identified as a cause of sea star wasting disease, which has been responsible for billions of sea star deaths since 2013 and widespread loss of kelp habitats. The findings, published in Nature Ecology & Evolution, could enable the development of recovery strategies for coastal marine ecosystems affected by this disease.

Sea star wasting disease leads to the disintegration of sea stars and affects over 20 species, including sunflower sea stars. Since it emerged in 2013, it has become the largest documented marine epidemic recorded in a non-commercial species, destroying populations of sea stars along the Pacific Coast of North America, from Mexico to Alaska. The loss of sea stars also enables populations of their prey, sea urchins, to rapidly expand and overgraze on kelp forests, which are critical habitats for a range of marine species. Over a decade of investigations into the cause of the disease have previously been hampered by the absence of visible pathogens in infected sea stars and a lack of fully unexposed and healthy individuals from wild populations.

Melanie Prentice, Alyssa-Lois Gehman and colleagues conducted seven controlled exposure experiments using wild and captive-bred quarantined sunflower sea stars, which indicated that a living non-viral agent was involved. Gene sequencing was then used to profile the microbial communities of diseased and healthy tissue from the sea stars. This led to the identification of the pathogen Vibrio pectenicida as a causative agent of the disease, which was confirmed in laboratory experiments in which sea stars were exposed to pure samples of the bacteria.

The findings will enable testing of this disease across environments and species, which will improve understanding of how it is transmitted and how it can be better managed in order to respond to outbreaks in the wild.