Scientists Uncover Cause of Sea Star Die-Off

Researchers have finally found the reason behind the deaths of over 5 billion sea stars during a decade-long epidemic.

Commonly referred to as starfish, these creatures typically have five arms, though some species can possess up to 24. They display a range of colors, from orange to purple to brown and green.

Beginning in 2013, a disease that has devastated sea star populations spread from Mexico to Alaska, leading to significant declines in more than 20 species. The Sunflower Sea Star was hit particularly hard, losing about 90% of its numbers within the initial five years of the outbreak.

“That’s really alarming,” remarked Alyssa Gehman, a marine disease ecologist at the Hakai Institute in British Columbia, who helped identify the disease’s cause.

She described that a healthy sea star has arms that are puffy and straight, while the disease causes lesions and eventually leads to the arms falling off.

The culprit has been identified as a type of bacteria that also infects shellfish, as detailed in research published in the journal Nature Ecology and Evolution.

Rebecca Vega Serre, a marine microbiologist at the University of California, Santa Barbara, stated that these findings address long-standing questions about serious diseases affecting ocean life.

It took more than ten years of research to pinpoint the disease’s origin.

Initially, some studies proposed that a virus might be responsible, but the densovirus thought to be involved was actually a common inhabitant of healthy sea stars and not linked to the sickness, as explained by Melanie Prentiss from the Hakai Institute, who co-authored the study.

Efforts to determine the disease’s cause often overlooked the real threat, focusing instead on tissue samples from deceased sea stars, which lacked vital fluids.

However, the latest study analyzed the coelomic fluid and discovered the presence of the bacteria Vibrio pectenidia.

“Tracing the causes of environmental diseases, especially underwater, is pretty challenging,” said microbiologist Blake Usimaima from the University of North Carolina Wilmington, who was not part of the study. He praised the team’s thorough investigation as “really smart and significant.”

With a clearer understanding of the disease’s cause, scientists have a better chance of intervening to assist the sea stars.

Prentiss mentioned that researchers can now test remaining sea stars for health and consider relocating them or reintroducing them to previously inhabited areas.

They can also explore whether certain populations might have innate immunity and if treatments like probiotics could enhance their resistance to diseases.

Such restoration efforts aren’t just crucial for sea stars but are vital for the entire Pacific ecosystem.

The sunflower sea stars, which may appear harmless at first glance, are voracious predators, consuming most of the organisms found at the ocean floor, according to Gehman, who remarked on their “greedy” eating habits.

With the decline of sea stars, populations of sea urchins tend to surge, often overwhelming approximately 95% of Northern California’s kelp forests within a decade. These kelp forests provide crucial food and habitat for numerous marine creatures, including fish and seals.

Researchers remain hopeful that these new insights will aid in the recovery of sea star populations and allow the kelp forests, often likened to “sea rainforests,” to regenerate.