By Lourdes Mederos, UF/IFAS Communications
A disturbing scene met snorkelers in Palm Beach County’s coastal waters – sea stars (also known as starfish) with missing limbs, open wounds and bodies falling apart on the ocean floor.
The condition known as Sea Star Wasting Disease has scientists concerned, suggesting its persistence and widespread nature requires further monitoring.
University of Florida scientists in Fort Lauderdale now confirm the cause as Sea Star Wasting Disease (SSWD), marking the first documented case in Florida’s Atlantic coastal waters and in the nine-armed sea star in a study just published in Southeastern Naturalist.
The discovery, made by researchers with the UF’s Institute of Food and Agricultural Sciences (UF/IFAS), represents a major expansion of the disease into the Atlantic Ocean. The disease has devastated starfish populations along the North American Pacific coast, from Mexico to Alaska, with significant die-offs in the Channel Islands and Gulf of Alaska, and has also been reported in Antarctica’s McMurdo Sound in 2019 and 2022; however, it has not been recorded in Florida’s marine ecosystem until now.
The disease has devastated sea star populations along the Pacific coast for over a decade, yet it has not been recorded in Florida’s marine ecosystem until now.
“Documenting when and where marine life are being impacted by disease is a critical first step to understanding the negative impacts and environmental stressors that threaten ecosystem health,” said Melissa Miller, a wildlife ecologist at UF/IFAS Fort Lauderdale Research and Education Center (FLREC).
Alex Romer, a quantitative ecologist at the FLREC, was snorkeling recreationally on July 6, 2024, when he spotted the outbreak along the waters of Lake Worth Cove in Palm Beach County.
He encountered dozens of nine-armed sea stars, normally common and healthy in these waters, showing signs of a fast-acting and fatal condition. The signs included curling limbs, dead tissue and, in many cases, bodies disintegrating into the sand.
“My area of expertise isn’t marine biology, and any observant snorkeler in Lake Worth Cove could have been in my shoes that day. I simply felt a responsibility to ensure this outbreak didn’t go unreported,” said Romer.
Nine-armed sea stars are more than just favorites among beachgoers, divers and snorkeling enthusiasts. As predators and scavengers, they play a vital role in ocean waters by turning over sediment and cycling nutrients. A decline in their numbers could ripple across the seafloor community, affecting the health of other marine species.
Romer returned the next day to document the outbreak and collect tissue samples. While some live sea stars survived, those that didn’t left behind only black, powdery imprints of their former shape.
DNA lab analysis revealed no trace of another sea star-associated disease known as densovirus, which was once suspected as a major cause of SSWD.
“This finding strengthens the scientific consensus that SSWD cannot be attributed to the densovirus alone,” said Romer. “If a pathogen is involved, it may be an entirely different agent. Alternatively, environmental stressors, such as extreme heat, salinity changes or pollutants, may be contributing factors.”
Sea surface temperatures in the area were more than 1°C (1.8°F) above average during the time of the event. Researchers also noted unusually low tides and nearby stormwater runoff, which may have intensified stress on shallow-water fish populations.
“When nine-armed sea stars forage, they churn the sand for worms and shellfish. If their numbers drop, that sediment-mixing slows, giving algae a chance to overgrow meadows. Thinner seagrass means fewer nursery spots for young sportfish,” said Romer.
Though nine-armed sea stars can grow back lost limbs, the rapid disintegration and high mortality observed are not typical behaviors for the species and are consistent with wasting disease pathology, said Romer.
“This event is now the southernmost confirmed case of SSWD in the Atlantic Ocean and expands the list of known affected species,” he said. “The findings raise new concerns about the vulnerability of Florida’s marine invertebrates and the need for continued monitoring.”
Romer encourages the public to report unusual wildlife sightings to the Florida Fish and Wildlife Conservation Commission at 888-404-FWCC (3922) or record them on community science platforms such as iNaturalist.
“Community reports give researchers an early warning for invasive species, wildlife disease, and threats to vulnerable species. The more people participate, the better scientists can spot opportunities for action. If you’re spending time in natural areas, bring a camera and a keen eye. Your observations matter,” said Romer.
Banner photo: A pair of nine-armed sea stars, Luidia senegalensis, crawl near the Blue Heron Bridge in Palm Beach County at night. (iStock image). This piece was originally published at https://blogs.ifas.ufl.edu/news/2025/06/18/nine-armed-sea-stars-dying-in-atlantic-waters-uf-ifas-scientists-document-first-case-of-disease-in-florida/.
