Deadly Bacteria Identified as Starfish Killer

Mystery Disease Ravaging West Coast Marine Life Finally Solved

A decade-long battle against a devastating epidemic threatening starfish populations along the U.S. West Coast has reached a critical turning point. Marine biologists have pinpointed a specific bacterium as the culprit behind the mysterious Sea Star Wasting Disease (SSWD), a scourge that causes disfigurement and ultimately death.

Unmasking the Microbe

Canadian and American researchers, publishing their findings in Nature Ecology & Evolution, have identified *Vibrio pectenicida* as the primary agent of SSWD. This pathogen, a distant relative of cholera bacteria, has been confirmed as the cause after extensive laboratory investigation. The research team focused on the microbial composition of both healthy and diseased starfish, isolating three key bacterial suspects from the *Vibrionaceae* family. *Vibrio pectenicida* was found to be overwhelmingly present in sick specimens and entirely absent in healthy ones.

Sunflower Star’s Plight Highlights Devastation

While at least twenty species of sea stars have succumbed to SSWD, the sunflower star, *Pycnopodia helianthoides*, has been particularly hard-hit. Southern populations off the coast of Mexico are now extinct, and those in northern waters near Alaska have dwindled to just over ten percent of their former numbers. The loss of this keystone species is triggering a significant ecological imbalance, leading to an unchecked surge in sea urchin populations. These urchins, normally prey for sunflower stars, are now “over-grazing” vital kelp forests in the Pacific, causing widespread habitat destruction.

Confirming the Pathogen

To solidify their findings, the scientists conducted crucial experiments. They isolated a specific strain, FHCF-3, of *Vibrio pectenicida* from the bodily fluids of infected starfish. Through meticulous testing, they confirmed this particular strain’s direct role in causing the devastating symptoms of SSWD.

Potential Link to Shellfish Farming

The precise origin of the bacterium remains under investigation, but researchers suspect a connection to commercial shellfish farming, particularly scallops. *Vibrio pectenicida* is known to infect scallop larvae, although a different strain is typically involved. Swan neck mussels, which share a strong genetic similarity to the FHCF-3 strain, have also been observed to be victims of the bacterium. This observation was noted in an accompanying *News & Views* article in Nature.

The long road to identifying the pathogen underscores the complexities of marine epidemiology. Few marine biologists specialize in this field, making the identification of underwater disease agents a lengthy process. As a comparison, the cause of the decline in the Californian Sea Power Shell took a decade to uncover, and the ciliate responsible for mass mortality in Caribbean Sea Insels during the 1980s remained a mystery for an extended period. The current perpetrator of the *stony coral tissue loss disease*, a grave threat to Caribbean coral reefs, is still unknown.

Future Conservation Efforts

With the culprit identified, the focus now shifts to potential solutions for starfish conservation. Future research may explore breeding starfish that are resistant to the bacterium or investigate bacteriophages—viruses that prey on bacteria—as a potential biological control agent. Until effective interventions are developed, hope remains for the remaining sunflower stars to be protected from the devastating effects of SSWD.