Something Is Killing Florida’s Manatees in Record Droves

Something Is Killing Florida’s Manatees in Record Droves
Photo: Eva Marie Uzcategui/AFP, Getty Images

Florida’s iconic manatees are in danger. The Florida Fish and Wildlife Commission said last week that as of May 21 almost 750 manatees have already died this year.

The current manatee mortality record was set in 2018, when 804 animals died, and this year is on track to crush that sad record. We don’t have that any manatees to spare: Before this year, there were only around 7,500 Florida West Indian Manatees left in the wild. That population could take a huge hit if deaths reach 1,000 this year, as some experts project they will. The last time there was a die-off this big was in 2010 when a cold snap caused 760 manatees to die.

It’s not totally clear what’s murdering the manatees, but there’s evidence of a number of factors involved. A big problem for the sea cows is that seagrass, their favourite food, is dying out, partially due to intense algae blooms that have been plaguing Florida for the past couple of years. Blue-green algal blooms — which are caused by nutrient-rich runoff from agriculture and other industries — have been regularly cropping up in the bodies of water the manatees inhabit. A red algal bloom, a natural occurrence that is supercharged by pollutants and other human factors, raged throughout the state in 2018, killing fish and closing beaches. Climate change is also heating up waters, allowing algae blooms to flourish as well.

The algal blooms are terrible news for the seagrass. Indian River Lagoon, one of the country’s most biologically diverse estuaries where thousands of manatees come to visit each year, has seen deadly red algae increasingly creep into its waterways over the past decade. Correspondingly, 58% of the seagrass in the lagoon has died off since 2009, the local river water management district said. Manatees, which weigh an average of 1,200 pounds (544 kilograms), need to eat between 60 and 54 kg (27 and 54 kilograms) per day. With seagrass being scarce, it seems like manatees may be quite literally starving to death, which is one of the saddest sentences I’ve ever typed.

When red tides invade manatee habitat, the toxins produced by the algae can accumulate in seagrass, providing another vehicle to kill the poor sea creatures. In 2013, an aggressive red tide killed more than 200 manatees.

There are also concerns about pesticide levels in the manatees themselves. A study published in March in Environment International sampled the plasma of manatees and found glyphosate, a widely-used herbicide and the active ingredient in weedkillers like Roundup, in more than 50% of the animals sampled. The study also found that glyphosate levels in manatees “significantly increased” between 2009 and 2019, possible due in part to sugarcane farming in the Florida Everglades. Chronic exposure to glyphosate, the study said, could have impacts on the renal systems of manatees, and weaken their immune systems as they’re being exposed to algae blooms or cold stress from changing temperatures.

Manatees dying out is, obviously, a huge bummer for sea cow fans. But trouble for manatees is also terrible news for Florida’s ecosystem as a whole.

“Manatees are literally that sentinel species,” Patrick Rose, executive director of the Save the Manatee Club (which, by the way, was founded by Jimmy Buffet) told CNN. “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.”

Even without widespread algae blooms and dwindling seagrass, it’s already pretty dangerous to be a manatee. The species have historically suffered from loss of habitat as well as collisions with powerboats. The Fish and Wildlife Service added them to the endangered species list in the 1970s when there were just a couple hundred manatees left in the wild in Florida. But in 2017, when populations were back up above 6,000, the Trump administration downlisted manatees from “endangered” to “threatened,” prompting outcry from conservation groups who say that we still have a long way to go to protect the slow-moving critters. This year’s die-off shows why that outcry is warranted.