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Just 78 days into 2021, the state has already reached 85% of the 637 manatee deaths logged for the entirety of 2020. — Florida Fish and Wildlife Conservation Commission report
WHETHER YOU LOVE OR HATE MANATEES, the sudden spike in manatee deaths this winter should cause concern for all Florida residents and visitors. While the images of dead manatees are shocking, their deaths are actually a symptom of a much larger ecosystem problem that imperils multiple facets of Florida’s economy.
The manatee mortality numbers this winter are largely driven by a die-off of seagrass meadows in the Indian River Lagoon (IRL) on Florida’s east coast. Seagrasses serve as the manatees’ primary food source, so many of the manatees wintering in the IRL are starving to death. But seagrass beds do far more for Florida than just feed manatees. According to the Florida Department of Environmental Protection’s website, seagrass improves water clarity by anchoring bottom sediments and provides shelter and food for juvenile redfish, sea trout, shrimp, bay scallops, crabs, lobsters and other species.
Property values and the coastal tourism business rely upon waters being sparkling clear and beautiful, with the chance to see charismatic creatures such as dolphins and manatees. Florida’s commercial and sport fishing industries rely directly on the output of fish and other species of seafood that grow up in the nurseries that seagrass meadows provide. The Florida Fish and Wildlife Conservation Commission estimates the statewide economic impact of recreational saltwater fishing alone at $9.2 billion with 88,501 jobs supported.
Most manatees show scars of strikes by boats, such as this one in Blue Spring that is missing part of its tail. COURTESY OF SAVE THE MANATEE CLUB
“With tourism being the main draw to Florida, a lot of people want to go fishing,” said Capt. Billy Norris, the owner of Pale Horse Fishing Charters in Southwest Florida and president of Tamiami Sportsman’s Coalition. “They watch the fishing shows on TV and the videos on You- Tube, but people aren’t going to want to go fishing with red tide and diminished fish populations. If fishing disappears, we’re in trouble.”
Water quality problems are a primary cause of why seagrass meadows are dying, with the IRL particularly impacted because of its location downstream from much of Florida’s heavily developed east coast. But Southwest Florida’s seagrass beds are also suffering from water quality issues and could soon experience a similar fate. Dying seagrass floating in the water doesn’t garner attention the way a floating, rotting corpse does, so the manatee serves as the 1,200-pound canary in the coalmine to alert us to the collapse of the seagrass ecosystem so critical to Florida’s greater wellbeing. What is bad for manatees is bad for Florida, its residents and its economy.
Boat strikes are a major cause of death among manatees, with only 4% of adults lacking boat scars and 25% of manatees carrying scars of at least 10 injuries caused by boats. COURTESY OF SAVE THE MANATEE CLUB
Manatee deaths and causes
As of March 19, the Florida Fish and Wildlife Conservation Commission reports a total of 539 verified manatee deaths. Just 78 days into 2021, the state has already reached 85% of the 637 manatee deaths logged for the entirety of 2020. Of the last two decades, 2020 ranked as the fourth most fatal year for manatees, with 2013 the worst year with 830 deaths. However, 2021 has already amassed nearly two-thirds of 2013’s death toll in under three months. January and February 2020 saw 143 manatee deaths, but the same two months this year saw deaths nearly triple to 416.
Manatees gather in warm water refuges in Florida during the winter. Many show scars from boat injuries. COURTESY OF SAVE THE MANATEE CLUB
Over the last decade, Lee and Brevard counties have consistently proven the deadliest for manatees, with the two counties swapping the number one spot back and forth during the last 10 years. As of March 19 of this year, Brevard has spiked to 235 deaths, with Broward second at 53, Lee at third with 39 and Palm Beach County at fourth with 33 deaths. Charlotte County has had one manatee death. So far, no manatee deaths have been recorded in Collier County this year.
Complicating the matter is that far fewer necropsies (animal autopsies) have been performed this year for a myriad of reasons, so conclusive data about the cause of manatee deaths isn’t being gathered. The reasons for the necropsy drop range from budget and personnel cuts to a higher incidence of live rescues, and then the pandemic added an additional complication since necropsies require a team of people wearing personal protective equipment that has been in short supply. For the last decade, the percent of manatee corpses that went without a necropsy ranged from a low of 2% and gradually rose to 21%. In 2020, that number jumped to 33%. So far this year, 69% of dead manatees have not received necropsies. For those that are not necropsied, death verification amounts to FWC personnel traveling to the corpse to log its length and sex.
“There’s extra effort going into rescuing manatees, which is fantastic, and the Fish and Wildlife Commission has been doing yeoman’s work out there,” said Patrick Rose, aquatic biologist and the executive director of the Save the Manatee
Club. “However, only about one in three is being necropsied, so there’s an awful lot we still won’t know for sure about what’s happening. We’re trying to get the Commission more support both for staffing and funding. In the long run, if this continues at these rates, it’s going to jeopardize the ability to defend the rules and protections and also come up with the proper solutions as to what the problems are because it is quite important to understand why they’re dying.”
Manatees had already lost some of their protections when the U.S. Fish & Wildlife Service reduced their endangered species status from endangered to threatened in 2017. Mr. Rose said scientists argued that downgrading the protection, based upon the species’ increase in numbers over several decades, was premature because no plan was in place to protect key resources the manatees needed for their continued viability. He said among the key resources that needed addressed were the seagrass beds that were collapsing even then in the Indian River Lagoon. An article from 2019 on the U.S. Fish & Wildlife Service’s website about algal blooms around the St. Lucie River, which drains into the IRL, mentions that algal blooms could indirectly affect manatees by shading out seagrass beds and causing them to die, but states that the “temporary loss of these feeding sites will cause manatees to feed elsewhere until the grassbeds return.” How- ever, by 2019, 50,000 acres of seagrass beds had died in the IRL, representing a substantial loss of food for both the manatees and other aquatic life forms that rely upon seagrass.
Rescued manatees being brought to rehabilitation facilities this winter show signs of emaciation from starvation, such as the scrawny manatee on the right that is so thin that the back of its skull ridge is visible as a “peanut head.” COURTESY OF SAVE THE MANATEE CLUB
Still, even without hauling a 1,000-pluspound carcass onto a trailer to transport to a lab for necropsy for the definitive, final cause of death, some factors of the manatee’s general condition can be apparent in the field. Manatees that are starving show signs of emaciation through a loss of fat in the neck area, resulting in the back of the skull being visible in a condition referred to as a “peanut head,” as well as loose folds of skin across the underside. Stress from cold temperatures shows up as white lesions on a manatee’s skin, especially on the fluke, snout and flippers. Whether such visible anomalies indicate the cause of death or are only contributing factors, such as a manatee being too weak from starvation to swim away from an oncoming boat, can’t be known without a necropsy or the implementation of a procedure to collect more data in the form of a partial “field necropsy.”
A manatee is released back into the wild after being rescued and rehabilitated. PHOTO BY HEATHER MURPHY / COURTESY OF SAVE THE MANATEE CLUB
“As humans, we’re always trying to point our finger at one thing, but there’s this concept that ecologists talk about of multiple stressors,” said Dr. James Douglass, associate professor of marine science in the Water School at Florida Gulf Coast University. “There may be one thing that’s the straw that breaks the camel’s back, but you can’t ignore all of the stresses that built up over time that allowed that last straw to be fatal. In many of these deaths there’s probably an interaction of multiple causes, and the death gets attributed to a single cause, such as cold stress, but perhaps this manatee has been sick since it’s last red tide exposure, malnourished because it doesn’t have as much grass as it used to, it’s got an old wound from the boat strike and the cold is what finishes off the manatee.”
A manatee rescued this winter shows signs of emaciation from starvation, evidenced by the folds of loose skin on the belly. COURTESY OF FLORIDA FISH AND WILDLIFE CONSERVATION COMMISSION
For the years within the last decade that lacked an unusual environmental event, such as a severe red tide or prolonged cold spell, most showed boat strikes as one — if not the — leading cause of mortalities for the year. Red tide shows up as one of the causes, or contributors, to death along the Southwest Florida coast but only rarely along the east coast. Although insufficient necropsies are being done to absolutely determine the causes of many manatee deaths this year, the FWC has acknowledged on its website that “initial assessments indicate the high number of emaciated manatees is likely due to a decline in food availability [as] seagrass and macro algae coverage in this region and specifically in the Indian River Lagoon has declined significantly.”
Shoal grass is one of the species of seagrass that grows in the seagrass meadows that provide not only food for manatees but also serve as nurseries for the fish, shrimp and crabs that Florida’s sport and commercial fishing industries rely upon. COURTESY OF FLORIDA ATLANTIC UNIVERSITY
Melody Kilborn, Southwest Region public information director for the FWC, replied to a request for additional information by sending an email with a link to the same FWC page about the unusual manatee mortality event on the Atlantic Coast, tips for how the public can help manatees and the following statement: “As you can imagine, our staff have been very busy out in the field working hard on this topic and many others. Unfortunately, I don’t have any research staff available today to provide a quote for you.” This proved to be a common theme among many working in manatee research; arranging interviews had to be delayed or simply proved impossible because of their front-line work attempting to rescue live manatees amid the current emergency.
While the IRL is where manatees are suffering most for lack of food, Capt. Norris has noticed manatees in Southwest Florida exhibiting unusual feeding behaviors.
“I’ve seen manatees in the last couple of years on the surface eating mangrove seed pods and brush that’s coming out on the outgoing tide, which should not be the case,” he said. “They should be eating seagrass on the bottom, not eating lawn clippings off the surface of the water. But they’re hungry, so they have to eat something.”
News that manatees are starving might prompt some kindhearted people to try to feed them. Not only is this illegal, but it’s also bad for the manatees. Beyond the fact that it would be necessary to purchase 150 pounds of lettuce — per day — to feed one manatee, feeding teaches them to associate food with humans, which puts them at even greater danger of boat strikes. It also encourages them to stick around after the weather warms, when they should be leaving their winter warm water refuges, spreading out and migrating to places where seagrass grows more plentifully. Even an officially organized feeding program is not currently being considered.
“We need to avoid that solution at all costs, and it would only have to be a last resort,” Mr. Rose said. “Fortunately for this season, it appears the warmth has come just at the right time. Those manatees need to be free to go, so the last thing we want to do right now is feed them in the Brevard County area because that would only cause them to want to stay there longer when they need to leave to go find food in more remote areas.”
Saving seagrass is the key, for manatees and more
Beyond making them reliant upon humans, just feeding manatees also fails to replace the functions the seagrass meadows serve and fails to help all of the other creatures that rely upon seagrass beds. Beyond feeding manatees and sea turtles, stabilizing bottom sediments and providing food and shelter for the juvenile fish and seafood that support sport and commercial fishing jobs, seagrass meadows absorb some — but not all — excess nutrients flowing off the land and even serve to sequester carbon dioxide from the atmosphere to help mitigate climate change. Researchers from the Florida Coastal Everglades program of the National Science Foundation’s Long Term Ecological Research Network determined that seagrass meadows sequester as much carbon into the soil below their roots as tropical upland forests do. That “blue carbon” could also release into the atmosphere if seagrass meadows die.
“For 25 years, at least, it’s been understood that if you really want to monitor the health of an estuary in Florida, look at the seagrasses,” said Dr. M. Dennis Hanisak, research professor and director of the Marine Ecosystem Health and the Indian River Lagoon Observatory programs at the Harbor Branch Oceanographic Institute of Florida Atlantic University. “When the seagrasses are doing well, the implication is all of the things that depend on it, like fishes, crabs and manatees, are going to be in relatively good health. That’s why there’s been a lot of monitoring of seagrasses and why we know how much seagrass was lost in the lagoon.”
As flowering plants, seagrasses need a lot of light for their photosynthesis process, so this is why they are vulnerable to water quality issues. The different types of seagrasses have evolved for the varied salinity levels of brackish water in estuaries, much like the different types of mangroves, so freshwater releases down canal systems can stress them. Algal blooms floating in the water shade out their sunlight. Harmful algal blooms are fueled by excessive quantities of nutrients flowing into the water, caused by anything from lawn fertilizer to leaky septic tanks to aging municipal sewage plants. Algae can also grow directly on seagrass, once again blocking the sunlight needed for the plants to produce their own food. Big boats or jet ski tour groups churning the water, causing turbidity, blow up silt and sand from the bottom that settles upon the seagrasses, coating their leaves to block the sunlight they need for photosynthesis. When the seagrasses can’t photosynthesize and have used up their stored foods, they die, releasing more nutrients into the water as they rot as well as releasing the bottom sediments their roots once held in place. Both lead to water quality becoming even worse. Spraying of herbicides in freshwater to kill invasive water plants or even to make holding ponds have clear-looking water flushes both chemicals and more nutrient-releasing rotting matter into estuaries.
Indian River Lagoon had suffered some seagrass decline in the 1980s, but programs to counter the decline had worked well until the early 2010s, when a series of harmful algal blooms hit. The first was a super bloom of phytoplankton, followed the next year by an algal bloom called brown tide. Dr. Hanisak said at least 60% of the seagrass in the lagoon was lost, and now the northern part of the lagoon is basically devoid of seagrass.
“Brown tide causes harm because it outcompetes everything else so it’s the only thing in the water, and it’s so small a lot of organisms can’t eat it,” said Dr. Michael Parsons, director of the Vester Marine & Environmental Science Research Field Station at Florida Gulf Coast University and a harmful algal bloom researcher. “If there were organisms trying to filter phytoplankton, like oysters or scallops, they can’t filter these cells out, so they starve to death. The cell number gets so high it cuts how far light can penetrate. The water is like a brown milkshake, so the seagrasses aren’t getting enough light, and it kills them. It can cause a whole ecosystem failure.”
While the east coast has suffered devastating seagrass losses, Southwest Florida has its own seagrass bed problems. Charlotte Harbor suffered a harmful algal bloom last year that impacted seagrass.
“It was this mucky green algae, on the eastern shore of Charlotte Harbor in particular, and it killed a vast amount of seagrass beds there,” Dr. Douglass said. “Particularly the deeper edge of the bed where it already wasn’t getting enough light, the seagrass got covered with this algae and died, so that it’s similar to what happened in the Indian River Lagoon where there was this critical event of a big algae bloom that knocked the seagrass way back. There is some seagrass surviving in Charlotte Harbor, but it was just decimated by this green algae bloom. Indian River Lagoon is in really bad trouble, but Southwest Florida, we’re headed that direction. It’s just going to take us a little bit longer to get as bad, but it’s pretty bad here now. We’ve already lost a lot of seagrass over here, too.”
Now in his late ‘30s, Capt. Norris has watched the changes that have taken place in the seagrass beds over his lifetime and is concerned.
“Twenty years ago, Estero Bay was awesome — there was grass everywhere,” he said. “As a kid 30 years ago, Big Hickory had seagrass all the way through it — it was beautiful. For lack of a less-disheartening word, it’s just decimated by pollution, the constant red tide from fertilizer, the runoff from the streets. We’ve reached maximum capacity of infrastructure and sustainability as far as the fishery goes.”
Capt. Norris said there were just two healthy seagrass beds left in Estero Bay, and the Tamiami Sportsman’s Coalition is in the process of fundraising and gaining permits to erect non-combustible motor zone signs to protect them from another danger to the seagrass beds — propeller scars. Much like boat strikes to manatees, prop scars to seagrass beds are largely avoidable if boaters take more care. He said the problem is largely that visitors are inexperienced with boating in Florida’s shallow waters. He learned from Dr. Parsons that it takes seven years for a seagrass bed to recover from the prop scar damage that happens in a few minutes, and he said he typically sees 10 or 15 boats a day get hung up in the shallows.
“You see these guys blowing over the flats — and it’s not malicious — they just don’t know it’s shallow,” he said. “They get stuck, burn their engine out trying to turn around, and blow all that out. Over time it adds up, little by little, whittling away at the seagrass, which directly affects the manatees because that’s what they eat.”
The blueprint for a way back from the brink exists. Tampa Bay suffered seagrass degradation in the 1970s but implemented programs to restore their beds. However, Dr. Hanisak said it takes 10 years to start seeing improvement in the seagrass beds and 25 years to reach restoration. Prevention is preferable to restoration, and creatures from manatees to redfish can’t wait that long.
“If you just look at boating, cold stress and red tide, that’s a pretty major trifecta of mortality, and now we’re adding malnutrition,” Mr. Rose said. “This is so frustrating as an aquatic biologist because we should never have been here. We’ve known what to do to not be here, but we didn’t do it. Now we have to find a way to do what we know can be done and must be done.” ¦
In the KNOW
Report injured, orphaned or dead manatee
Call 1-888-404-FWCC (1-888-404- 3922) on a landline
Dial #FWC on a cellphone
VHF Channel 16 on a marine radio
Be prepared to provide information for the following questions:
Is the manatee alive or dead?
When did you see the manatee?
What is the exact location of the manatee?
How long have you observed the manatee?
What is the approximate size of the manatee?
What is the location of the public boat ramp closest to the manatee?
Does the manatee have a “tag” attached near its tail?
Can you provide a contact number where you can be reached for further information?
After contacting the FWC’s Wildlife Alert Hotline, a manatee biologist will call you back to the number you provided. In the meantime, please take pictures and/or a video of the manatee to send to the biologist. This footage can assist in determining what is wrong with the manatee and/or to help identify the individual through any unique characteristics if it happens to leave the area prior to further evaluation of its condition.
Source: Florida Fish and Wildlife Conservation Commission
In the KNOW
How to protect seagrass
Avoid prop scars: Use only a pole or electric trolling motor over seagrass beds
Don’t fertilize your lawn during rainy season
Use mechanical methods to clear plants out of water instead of spraying herbicides
Certain plants and fishes can be introduced into ponds to keep them clean
Talk to your HOA about implementing these more environmentally friendly procedures
Source: Article interviewees
In the KNOW
Save the Manatee Club 407-539-0990 www.savethemanatee.org
Tamiami Sportsman’s Coalition 321-626-7541 www.facebook.com/ tamiamisportsmanscoalition
Boating safely around manatees
Have someone designated as a “manatee lookout” on your boat.
Look for “footprints” left in the water by manatees (those circle patterns left on the water’s surface).
Wear polarized sunglasses to better see manatees underwater.
Last but not least: GO SLOW in manatee zones and in shallow water, following all posted signs.
Never give a manatee food OR water, as it teaches them to seek out human interaction.
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