Manatees congregate in warm waters near power plants as U.S. winter storms graze Florida

RIVIERA BEACH, Fla. — A polar vortex that has hit much of the U.S. with ice and snow has dealt a glancing blow to Florida, dropping coastal temperatures and causing the Sunshine State’s manatee population, still recovering from a mass starvation event several years ago, to seek warmer waters.

Besides inland natural springs, a popular destination for the docile aquatic mammals is the warm-water outflows of about a dozen power plants around Florida. Manatees have been attracted to the warm-water discharges for decades, following a watery travel route that mother manatees have taught to manatee calves. Public viewing areas are located near power plants in Riviera Beach, Fort Myers and Apollo Beach.

Dozens of the sea cows, which can grow up to 10 feet (three metres) long and 1,200 pounds (544 kilograms), have been congregating for the past week near Florida Power & Light Company’s Riviera Beach plant, where the company opened the Manatee Lagoon attraction in 2016. The two-storey, 16,000-square-foot complex is free and open to the public. They’re hosting a family friendly ManateeFest on Feb. 1.

“Manatees are such a special species that we have in our waters here in Florida, because they are a sentinel species, which means that they’re an indicator for any water problems that we may have or any environmental issues we may have,” Manatee Lagoon education manager Rachel Shanker said. “They’re kind of the first animals to start to respond to any changes in the environment. And because they’re so charismatic, people really take note of that.”

The facility is open all year, but the best chance to see the animals is from Nov. 15 to March 31, when Florida water temperatures can drop below 68 F, which is deadly to manatees. While boating collisions are the top man-made threat to manatees, cold stress is the most common natural threat.

“So during the power generation process, that power plant puts out clean, warm water, and that warm water draws the manatees in when it gets cold,” Shanker said.

Ocean water is sucked in from the bay and used to cool the plant, but no chemicals or other substances are added to the water, Shanker said. The warm water discharged from the plant is the same ocean water, just warmer, and completely safe for wildlife.

The number of manatees near the power plant can fluctuate, but Shanker said Friday that the most they’ve counted this year is about 85.

“The manatees come here to Manatee Lagoon for that warm water, but we don’t have a large population of seagrass right here on our property,” Shanker said. “And so they’ll come here to Manatee Lagoon to get warm, then when they start to get hungry, they will travel out to find those seagrass beds, and they’ll go feed until they get full, and they get cold, and they’ll come back to our warm water to get warm.”

According to the Florida Fish and Wildlife Conservation Commission, 565 manatee deaths were recorded in 2024, similar to the 555 deaths recorded a year earlier. Those numbers are down significantly from 2021, when officials recorded over 1,100 manatee deaths, mostly caused by starvation. Pollution from farm, urban and other sources has decimated the seagrass on which the animals depend.

“The centre of those problems was in the Indian River Lagoon, where over the years, they’ve had these problems with all these algal blooms,” FWC manatee veterinarian Martine de Wit said. “And that affected the water clarity and quality, and seagrass had died off in that area.”

Indian River Lagoon is located along the Atlantic Coast in central Florida. State waters are home to more than 8,000 manatees with at least a third living or migrating through Indian River Lagoon.

State wildlife officials tried to mitigate the casualties by temporarily feeding lettuce to manatees. After two especially deadly winters, seagrass in the area began to recover, and manatee deaths have dropped.

“Seagrass is resilient, and it came back on its own, and manatees found it,” de Wit said.

While overall deaths have come down over the past two years, records show a spike in dead calves for this past year. The seagrass famine left many manatees so malnourished that they were physically unable to reproduce for several years, de Wit said. When the food returned, those previously starving animals all began reproducing at the same time.

“When you have higher pregnancy rates, more manatees being born, you always have a proportion that does not make it,” de Wit said. “I think that was just a measure of the reproduction coming back after all those lean years since 2020.”

The U.S. Fish and Wildlife Service on Monday rejected efforts by several Florida environmental groups to get the manatees back on the endangered species list. The manatee was downgraded from endangered to threatened in 2017 and will remain in that classification.

Florida’s manatee population is recovering, but officials and residents need to remain vigilant in protecting the threatened species, de Wit said.

“We always look into the future, and there are significant threats to manatees statewide,” de Wit said. “It’s looking better now, but you cannot sit back and watch it unfold, because we know it needs management and conservation efforts to protect them.”