Manatees are dying in droves this year. The die-offs could spell trouble for Florida

The Indian River Lagoon, pictured here in 2017, is in extreme environmental distress, and it's impacting the lives of hundreds of manatees that live there. By Scottie Andrew, CNN

(CNN) -- Despite their portly frame and inherent meekness, Florida's manatees are survivors.

When power plants began popping up along Florida's East and West coasts, manatees learned to follow the flow of the unseasonably warm water.

When boats with sharp motors increasingly flooded their habitats, they learned how to live with debilitating injuries, or tried to.

And when their favorite source of food began to disappear when toxic algae infested the water, they learned to eat less, often at the cost of their health.

Their gentle nature belies a deceptive resilience. Unathletic as they may seem -- they tip the scales at around half a ton -- they're built to endure.

But how much more can one species take?

Decades of environmental stress culminated this year in one of the worst manatee die-offs in recent history: As of May 21, at least 749 manatees have died in Florida in 2021, in what the Florida Fish and Wildlife Conservation Commission has called an unusual mortality event, or UME.

Manatee advocates who've sounded the alarm for years saw it coming.

"Manatees are literally that sentinel species," says Patrick Rose, executive director of the Save the Manatee Club, a 40-year-old nonprofit co-founded by Jimmy Buffet. "They're warning us of what else is going to come if we don't do a better job while there's still time to do something about it. If we don't, our own lives will suffer."

Florida, the third-most populous state in the US and still growing, stands to lose more than its state marine mammal if manatees go extinct. The same issues that have caused their mass deaths are disrupting freshwater and saltwater sanctuaries, killing off fish and other species and mucking up the water that millions rely on for their livelihoods. Florida beaches are now as well known for red tide as they are for pristine white sand and watercolor sunsets.

Rose thinks around 1,000 manatees could wind up dead by the end of the year. If manatees continue to die at such a rate, with an estimated 7,500 animals left in the wild (before factoring in this year's deaths), it could be only a matter of years left to save them -- and clean up Florida's water.

A sea of problems faces manatees

West Indian manatees had been on the mend for many years before their fortunes changed. Their recovery from near-extinction in the 1970s to a population over 7,000 was heralded as a victory for conservation. The US Fish and Wildlife Service, in a decision that proved controversial, even downlisted the West Indian manatee from endangered to threatened in 2017 due to the major population gains.

But problems had been bubbling below the surface for decades, and in 2021 it seems they've boiled over. The stressors facing manatees are numerous and entwined, and one can't be conquered without addressing the other, said Michael Walsh, a clinical associate professor at the University of Florida College of Veterinary Medicine who specializes in aquatic animal health.

The trouble, Walsh says, begins in the water.

When nutrients from wastewater or runoff containing fertilizers, microplastics or toxic chemicals leach into a manatee's marine habitat -- whether freshwater or saltwater -- they can throw off the balance of the water and cause harmful algae blooms to form.

The blooms blanket the surface of the water and shade out the seagrasses underwater that rely on the sun to survive, killing the grasses.

The seagrasses that survive the malevolent blooms are then overgrazed by manatees whose sources of food have shrunk, so the plants can't quickly regrow and continue to feed the manatees, Walsh said.

And when seagrasses die, gone is the manatee's favorite food source. They may start to nosh on other plants that don't fortify them the same way, or make do with less food (manatees should eat somewhere around 10% of their body weight per day, which translates to about 100 pounds of grass for an 1,000-pound adult manatee) and begin to lose weight. Over time, this leads to malnutrition and, eventually, starvation, Walsh said.

While climate change is generally warming water temperatures, warmer temperatures can foster the growth of harmful algae, which may kill seagrasses in their favorite warm water oases. So manatees may travel hundreds of miles until they find a new source of food and, hopefully, warm water. But the colder it gets, the more food they'll need to consume to stay warm, Walsh said. If there's less food, they'll succumb more quickly to cold stress -- for their impressive girth, they don't have enough blubber to keep themselves warm when the water temperature drops below 68 degrees Fahrenheit.

What's more, manatees have learned to rely on the warm water outflows from power plants on both coasts of the state -- about two-thirds of all manatees stay warm this way, according to a 2013 estimate. If those plants close as the state transitions to more sustainable energy sources, manatees will lose a reliable haven for warmth, leaving them with few options for wintering, Rose said.

There's also the problem of people: Florida has around 21.4 million residents, according to a 2019 Census Bureau count (a figure that may be higher now, given the number of Northeastern expats who moved down during the pandemic). Couple unimpeded population growth with an infrastructure system the American Society of Civil Engineers described as "deteriorating," and the pressure on water treatment systems in the state can be debilitating.

"Add up starvation, together with red tide, severe cold weather mortality ... these are just absolute catastrophic losses that they may never be able to recover from," Rose said.

Just under 90 manatees have been rescued in 2021 so far, according to the Florida Fish and Wildlife Conservation Commission. But most manatees who've died have not been necropsied, and some of their bodies were too decomposed to study, according to the commission's preliminary mortality report for the year.

The last comparable unusual mortality event occurred in 2010, when temperatures in Florida fell to historic lows in a cold snap that proved extremely dangerous for manatees. More than 760 manatees died that year, according to the FWC.

But 2021's count is already approaching that number, and the year isn't even halfway through.

What went wrong in manatees' favorite habitat

Perhaps no ecosystem in Florida is a better example of the dire state of the manatee than the Indian River Lagoon. An ecologically rich estuary that spans more than 150 miles along the East Coast -- enough room for manatees to forage and raise their calves without bumping snouts -- more than one-third of the country's manatees call it home at some point throughout the year.

But just as decades of human-made environmental degradation have caught up with manatees, the Indian River Lagoon is dying, too. An estimated 58% of the estuary's seagrasses have died in the last 11 years, according to the St. Johns River Water Management District, a regulatory agency that oversees the Indian River Lagoon.

Some parts of the lagoon are rife with microplastics, or small pieces of plastic that may never fully break down, even more so than in other well-tread waterways in Florida. A 2018 study found that crabs and oysters in Mosquito Lagoon, part of the Indian River Lagoon system, contained averages of 4.2 and 16.5 microplastic pieces per individual, the highest volume of microplastics recorded in invertebrates at the time.

As with manatees, the pollution, algal blooms and poor water treatment infrastructure are likely responsible for the Indian River Lagoon's problems, too, says Duane De Freese, marine biologist and executive director of the Indian River Lagoon Council and the Indian River Lagoon National Estuary Program.

Now, parts of the lagoon resemble a graveyard. CNN affiliate WPEC shared photos in early May of manatees washed up on the shore of the Indian River Lagoon, their bodies like deflated balloons. Their bones, picked clean by vultures, were haphazardly strewn across the sand where they'd washed up.

Manatee deaths are simply a "symptom of a system that is under stress and near collapse," De Freese said.

"This is about more than just the environment," he said. "It's about human health, it's about quality of life, it's about the economic vitality of our coastal communities. And if we fail to act in a science-driven way to solve these problems, as the population grows, these problems will grow with it."

And the natural elements that Floridians treasure -- clean water, fresh seafood, tourism, robust fisheries and, naturally, manatees -- will decline along with the environment, he said.

Saving the Indian River Lagoon requires money, which De Freese says is lacking. Though Gov. Ron DeSantis has passed laws like the Clean Waterways Act, which would fund projects to reduce nutrient pollution in vulnerable waters, overhauling the state's water infrastructure requires more than one bill, De Frees said.

But water quality and conservation is becoming a bipartisan issue among Florida lawmakers.

Republican Rep. Brian Mast and Democratic Rep. Stephanie Murphy introduced a bill in Congress this month that would improve federal funding for research and rehabbing of manatees and other marine life. The Palm Beach Post reported that Florida members of the House of Representatives wrote to President Joe Biden to ask for "robust funding" to support the Everglades, where some manatees spend their winters. Biden has confirmed his proposed infrastructure bill would be used to protect and restore the Everglades and other "major land and water resources."

Although "the ship turns a bit slower" up in Washington, De Frees said, support among lawmakers for cleaning up Florida's waters is good news. Those policies just need to be implemented quickly -- within the next few years, really -- to make a difference.

Novel solutions could be key to saving them

Saving Florida's manatees -- and restoring Florida's water quality -- has inspired a cooperative, occasionally tenuous relationship among manatee advocates and agencies, from Rose's Save the Manatee Club and the US Fish and Wildlife Service to veterinarians like Walsh and even US Geological Survey biologists who study the way polluted water impacts manatee health.

Also a recent addition to that crew -- farmers.

Jim Anderson lives in Ruskin, a coastal community known best for its tomato crops (and tomato festival). But about 25 years ago, after he noticed nearby seagrass beds were being torn up by boat propellers, Anderson switched from farming sod to farming seagrasses.

Since then, Anderson has operated a seagrass nursery for his business, Sea & Shoreline. He and his team grow half a million plants of 150 varieties, suitable for freshwater and saltwater. Seagrass restoration is a new industry in the state, and there's room for collaborators, he said.

In regions of freshwater and saltwater habitats where seagrass cover is sparse, Sea & Shoreline will plant seagrasses and place a protective cage over them to keep hungry manatees from eating them before they've taken root. Every few weeks, a dive team cleans the cage and mows the grass to foster its growth, he said.

Anderson and his team have found success already in another favorite spot of manatees -- Crystal River in western Florida. Sea & Shoreline has planted over 50 acres of seagrass there in the last four years and vacuumed up the toxic algal blooms. It's restored the pristine water clarity that lent the river its name, he said.

"It's expensive to do it, but how expensive is our water quality?" he said.

The prognosis of Florida's beloved 'sea cow'

Manatees would prefer not to fight for survival. They float through the water unrushed, soaking up their surroundings like bulbous gray sponges with snouts. Unlike the more aggressive dolphins or sharks of Florida, manatees do not provoke conflict. They'd rather flee, almost apologetically, than upset another creature.

But manatees have had to fight for decades. It's a battle they've won before through persistent conservation efforts, though humans are as much their downfall as their salvation.

Rose, now 70, has spent the last 40 years advocating on behalf of the "sea cows." He's seen their numbers shrink to less than 1,000 and bounce back again. Rose is "not willing to accept that we can't fix this," he said.

"But, I will tell you," he said, "it's going to be really, really hard."

Having delayed his retirement indefinitely to continue his work, Rose has some hope for the manatee's survival. Walsh and De Freese do too, and Anderson is optimistic that his seagrass restoration will continue to pay off for Florida's sea cow.

They're but four men in the campaign for manatees' survival. Local activists, Floridians who treasure their coasts and the life that relies on clean water, have kept the heat on officials to help save manatees. Their work continues until the day manatees can graze and swim and feel comfortable in the home they share with humans -- a day, manatee defenders hope, that will come while manatees still have some fight left.

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