Florida’s manatees starving to death
Lush seagrass gardens giving way to deserts
BREVARD COUNTY, Fla. – A sunbleached skull, scattered ribs and the decaying husks of dozens of manatees sully the smooth tan sand on a handful of mangrove islands north of Manatee Cove Park in Brevard County.
The emaciated remains, reported by waterfront residents or spotted by boaters, have been collected and dumped on the sandy outcroppings by state wildlife officers, turning these idyllic tropical settings into sea cow mass graveyards.
The smell of death hangs in the air. Vultures own the sky above as they circle what is quickly becoming an environmental catastrophe.
Up and down the Sunshine State, manatees, the gentle giants of the inland waterways, are dying en masse. They are starving. The mangrove coves and canals that once were havens for the creatures are increasingly empty of them. Decades of conservation success have given way to jumbles of bones and carcasses all around Florida.
“I think it will be the highest (number of manatee deaths) we’ve ever documented,” said Martine de Wit, who runs the Florida Fish and Wildlife Conservation Commission’s marine mammal pathology lab in St. Petersburg.
Who or what is responsible?
We humans, the residents of and visitors to Florida, own the reasons all this is happening, biologists say. Evidence from the massive die-off suggests this is a completely human-made famine. The sewage, detritus and fertilizers we have been dumping into our coastal waters for decades have created blooms of bad plant life while choking to death the seagrass on which the manatees and other marine life depend.
At the same time, our power plants lure manatees to winter farther north than they otherwise would be, increasing their risk of starving before seagrass grows back in the spring.
Once upon a time, biologists were sure it was mostly speeding boats and their propellers that threatened to wipe out manatees. It was a problem we could fix, and indeed speed limits, manatee crossing signs and fines made a positive impact, biologists say. Manatee numbers rebounded.
This problem — the loss of habitat and food — is not so easily remedied.
‘Ground zero’ is central Florida
While manatees throughout Florida are being impacted by famine, Brevard County hosts the largest population in the state and has become “ground zero” for the tragedy.
Already 696 manatees have died in 2021, triple the average number of deaths for this time of year. That’s more than one in 10 of the known manatees counted by biologists. The most deaths by far — 292, or 42% — were in Brevard County and the Indian River Lagoon.
Decades of runoff from septic tanks and fertilized front lawns, as well as sewage leaks, eventually changed the balance of life in the closed system of the lagoon in such a way that the grasses and microorganisms that supported them died out and didn’t come back.
The bottom — like increasingly more places statewide — is grassless, leaving a desert where once a garden for manatees thrived. And not just for manatees: As the seagrass that anchors the food web of Florida’s coastal waters disappears, it impacts the lives of sea turtles, shrimp, fish and crabs, too.
The die-off has not been terrible for all creatures. It’s been good for vultures and marine scavengers. Horseshoe crabs now reign supreme in the area.
But the negative fallout is huge and can be measured in dollars as well as lost animal life. Tens of billions in yearly tourism revenue is at stake. Lush seagrass spawns a lucrative saltwater fishing industry and ecological tourism, including people who come from near and far to see manatees and catch glimpses of mothers and calves grazing or leisurely moving through the waterways.
The fallout of famine
Before the coronavirus pandemic, dead manatees would end up with de Wit at the marine mammal pathology lab in St. Petersburg. There the veterinary pathologist would dissect and test to figure out why the creatures were dying. But this year, two-thirds of the dead never made it to her.
Coronavirus rules preclude too many examiners in the lab at once. So FWC biologists examined sea cow carcasses in the field when they could get to them, which wasn’t all the time.
The known causes of death this year include cold stress and natural causes.
But de Wit and most biologists studying the problem see one fact underlying the phenomenon: the loss of tens of thousands of acres of seagrass.
In the Indian River Lagoon alone, two phytoplankton blooms devastated seagrass in 2011, followed by two years of brown algae blooms, ultimately killing 47,000 acres of seagrass, or about 60% overall in the estuary. Not much has grown back since.
As seagrass withers statewide, manatees have little to eat, leaving them vulnerable to disease, cold and starvation. An adult manatee eats 100 to 200 pounds of seagrass per day to survive.
“Of all the events I’ve gone through myself, this one makes me wonder what are the long-term health effects on manatees with prolonged starvation,” de Wit said. “I’m not as optimistic as I was.”
Ironically, the manatees’ dramatic comeback after boating rules changed may have made things worse in the face of the looming environmental disaster.
As the state’s manatee counts doubled over the past two decades, boating advocates like Bob Atkins of Merritt Island warned wildlife officials that seagrass growth wasn’t keeping pace and manatees faced imminent famine. Boaters for years shouldered too much of the blame for the manatee’s plight, Atkins and fellow advocates said.
“This situation is tragic but not a surprise,” said Atkins, president of the boating advocacy group Citizens for Florida’s Waterways.
This year’s FWC stats show boaters being responsible for 4.8% of the manatee death toll. They typically cause 20% to 25% of the deaths on any given year. Boats have killed 34 manatees in 2021, just one fewer death than the state’s five-year average.
Boaters point to power plants, too. Manatees migrate to natural warm water refuges like freshwater springs but also to artificial ones, such as the warm-water discharge zones at power plants. That puts them in areas with scant seagrass during colder months. Before power plants, manatees seldom migrated farther north than Sebastian Inlet on the east coast and Charlotte Harbor on the west, fossil records show.
But in Brevard County, hundreds of manatees huddle flipper to flipper each winter at Florida Power & Light’s plant in Port St. John, keeping them farther north than they’d otherwise be.
“We’ve been warning the agencies for years that either we eliminate the artificial warm-water outflows (at power plants) and risk some manatees not returning to natural migration and at risk of cold stress mortality, or do nothing and keep stressing the system until the loss of seagrass threatens the life of the IRL (Indian River Lagoon) itself and everything dies including many more manatees,” Atkins said.
Manatees die when water dips below 68 degrees Fahrenheit for too long.
A special state and federal task force looked at the issue of warm water discharges at 10 power plants luring manatees too far north in the winter but little action has come thus far from the initial draft plan they put out in 2004.
In October, the task force issued another action plan that includes restoring flow to springs and developing other warm-water habitats not dependent on industry, gradually decreasing manatee dependence of power-plant discharges. That way sea cows will have time to adapt to new warm-water networks.
But the proposals are too late to stop what’s happening now. The death toll was so bad that last month, the National Oceanic and Atmospheric Administration declared Florida’s manatee die-off an “unusual mortality event,” potentially freeing up federal money to look deeper into the matter.
Disaster decades in the making
Seagrass and sea cows led a balanced coexistence in the Indian River Lagoon but in 2011 algae blooms began to ramp up yearly, blocking light, choking out oxygen and eventually killing off more than half the waterway’s seagrass.
“We are witnessing the impacts of a destabilized Indian River Lagoon food web,” said Duane DeFreese, executive director of the Indian River Lagoon National Estuary Program. “There are no quick fixes to this problem. If food resources decline, animal population size will adjust to carrying capacity.”
Manatees at first adapted to the seagrass loss, shifting their meals to whatever drift algae was left. But that changed the mix of bacteria in their guts, resulting in a bizarre sort of “toxic shock” that caused an acute, fatal cardiovascular syndrome. The manatees drowned as a result, and in 2013, 830 manatee died statewide.
Most biologists predict this year’s death toll will far surpass that record.
DeFreese is optimistic the situation can be reversed — and manatees can be saved — if municipalities and residents can manage to improve water quality in the long term. For that to happen, local governments need to get more aggressive in keeping sewage and runoff from Florida’s coastal waters, he said.
But for Pat Rose, the executive director of Save the Manatee Club, that’s not the first order of business.
“First priority must continue to be given to the rescue and rehabilitation of sick or injured manatees,” said Rose.
He long has criticized Florida for lack of action on preventing manatee deaths near power plants and for removing federal protection from the animals.
“I fear that the FWS is preoccupied with rashly removing the manatee from the endangered species list altogether rather than ensuring that imperiled manatees are truly and fully recovered,” Rose said.
Long road to recovery
During a recent kayaking trip on the lagoon, there were no live manatees visible along the vast shallows south of the space center. There was only the dead.
Donna Kirk of Winter Park had no idea just how bad it was until she explored these islands by paddle board.
“I had heard they were starving, but I didn’t know it was to this degree,” Kirk said.
Their remains should be left alone. Anyone caught taking manatee bones could face a 2nd degree misdemeanor for possessing parts of a federally protected species. Penalties can be severe.
And despite the ongoing famine, biologists warn against feeding manatees. Doing so keeps them lingering in grassless areas.
Green shoots of hope reign eternal for both seagrass and sea cow.
But de Wit said their road to recovery will be long. “When you go through prolonged starvation, it is sometimes impossible to turn the body around, even when you start eating again,” she said.
The hope is that nature will find a way.