For the second year in a row, more Florida manatees died than normal as the species battles a human-caused seagrass famine.
At least 800 manatees died statewide in 2022 after hundreds succumbed to starvation and malnutrition on Florida’s Atlantic coast last winter, according to preliminary data released this week by the Florida Fish and Wildlife Conservation Commission.
That follows the record-breaking 1,100 manatee deaths in 2021, caused in large part by decades of pollution-fueled seagrass loss in the 156-mile Indian River Lagoon, often considered one of North America’s most biodiverse estuaries. The 800 deaths exceeds the five-year-average of 741 manatee deaths per year, a number that increased after 2021′s die-off.
“Manatee mortality is getting substantially worse,” said Pat Rose, an aquatic biologist and executive director of the Maitland-based nonprofit Save the Manatee Club. And it’s directly related to decades of nutrient pollution, he said.
“It should be a warning that Florida could be facing more of this in the future,” Rose said.
Manatees spared from red tide blooms
While starvation and chronic malnutrition remain the leading cause of death on Florida’s Atlantic coast, there are likely a few reasons 300 fewer manatees died last year compared to 2021: a relatively warmer winter caused less stress on the species; there may now be a smaller manatee population after 2021′s mass die-off; and biologists verified fewer carcasses on the east coast last year, according to wildlife officials.
But the largest reason the death toll was lower in 2022 was less-severe red tide in the Gulf of Mexico this past year. While widespread toxic red tide blooms killed 84 manatees in 2021, just four manatee deaths have been linked to red tide last year so far, preliminary data shows.
“The red tide numbers will turn out much lower than 2021 because there was really no red tide bloom for most of the year — it only popped up in October after Hurricane Ian,” Martine deWit, the state’s manatee veterinarian based in St. Petersburg, wrote in an email to the Tampa Bay Times on Wednesday.
There are still necropsy tests awaiting results, so a few more red tide-related manatee deaths may be verified over the next few weeks, deWit said. But for now, the four manatee deaths from red tide occurred within roughly the last month of the year — when red tide blooms were at their peak in the Tampa Bay area.
Biologists located two dead manatees in Boca Ciega Bay in Pinellas County five days apart between Dec. 13 and Dec. 18, according to wildlife data. Two other manatees, one in Collier County and one in Sarasota County, are also suspected of having died from red tide blooms, according to wildlife officials.
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Manatees can die from red tide-related causes after inhaling toxins while swimming through a bloom. Or they can become ill after eating seagrass covered in the toxic stew.
The public also needs to remember that boat strikes are still a concerning cause of death for the marine mammals, Rose said. At least 76 manatees died in 2022 after being struck by boats, data shows.
Last year also brought with it another unsettling trend for manatee deaths: Researchers verified at least 19 deaths of manatees that were crushed or drowned in human-made water control structures like locks and dams. That’s the highest number of structure deaths since the state began keeping the data in 1974, according to the wildlife commission.
One theory to explain the increase in flood-gate deaths is a possible change in manatee population distribution, according to Rose.
Lettuce still on the menu for starving manatees
During a news conference in Bonita Springs on Tuesday, Florida Gov. Ron DeSantis said the state is vying to secure $100 million annually to improve water quality in the Indian River Lagoon. Seagrass coverage has declined 75% in the estuary between 2009 and 2021, according to data from the St. Johns River Water Management District.
With manatees facing unprecedented starvation, state and federal wildlife officials last year launched the first-ever manatee feeding trial to supplement the animal’s lacking diets with hand-fed butterleaf and romaine lettuce. On Dec. 16, the feeding began once again in Brevard County at the Florida Power & Light Cape Canaveral Clean Energy Center.
As of Wednesday morning, state biologists have put out roughly 30,000 pounds of lettuce into the cordoned feeding area, according to Michelle Pasawicz of the Florida Fish and Wildlife Conservation Commission.
There’s little evidence so far to determine whether the feeding trial has worked to stave off more starvation deaths, but biologists hope it’s making a difference.
“I’d like to think that our feeding program at least helps some manatees and has staved off some of those mortalities,” said Tom Reinert, a regional director with the wildlife commission, during a call with reporters Wednesday.
“We’re reaching quite a few animals at the feeding site.”