If you’ve seen a manatee lately – surfacing in a ring of river water, basking in their namesake park in Lee County or drifting the Gulf – odds are the creature has herbicide coursing through its veins.
To the list of woes plaguing the warm-blooded mammals, already dying in droves from red tide, boat collisions, habitat loss and scarce food, a paper released last week adds glyphosate.
Researchers found the weed-killer, the world’s most-used pesticide, in more than half of all Florida manatees the study sampled.
In the first three months of this year, more than 539 manatees have died in Florida, an alarming rate, says Pat Rose, who directs the nonprofit Save the Manatee Club.
“This is one more serious reason for concern that long standing human caused exposure of fertilizers, human waste and other byproducts are endangering our aquatic ecosystems and the species that depend on them for their survival,” Rose wrote in an email.
When they tested the sea cows’ blood, researchers found the substance, the active ingredient in Roundup and Rodeo, in the plasma of 55.8% of the creatures, and that concentrations of glyphosate in their plasma went up in the decade between 2009 and 2019.
The same level of glyphosate exposure manatees experience can cause kidney and liver damage in laboratory animals, which concerns Calusa Waterkeeper John Cassani.
The creatures’ chronic exposure in Florida waters may impact their immune and renal systems, further compounding the stress caused by other environmental factors, such as harmful algal blooms and cold weather.
“Manatees are Exhibit A that Florida’s waters are in crisis and they shouldn’t be facing this kind of pesticide threat,” said Jaclyn Lopez, Florida director of the Center for Biological Diversity in a statement. “Our beloved, chubby sea cows are dodging boat strikes, reeling from red tide and starving in the Indian River Lagoon because of water pollution. It’s heartbreaking to add chronic glyphosate exposure to the list of factors threatening manatee survival.”
Because glyphosate’s harm threshold isn’t yet clear, humans must do a better job of keeping it and other plant-killers out of waterways, Rose said – not just because they might harm the animals, but because they also deplete their food supply by causing harmful algae blooms that can shade out and kill manatees’ pastures.
“With such catastrophic losses of seagrasses it will be all the more important to protect our freshwater vegetation which can be further stressed by continued direct applications of glyphosate as well as runoff from upland applications in association with agricultural activities,” Rose said.
Published in the journal Environment International, the study found manatees were exposed to glyphosate in non-agricultural areas, such as the Crystal River, and that exposure was higher during winter, when manatees depend on the warm water refuge.
However, some question the paper’s underlying premise and some of its subsequent conclusions.
Two things, especially stand out.
The study says that Lake Okeechobee is polluted by pesticides and fertilizer that flow into its water from farm fields to its south. “(Lake Okeechobee) receives nutrient loads and other pesticides from the Everglades Agricultural Area,” the authors write.
Except it doesn’t, says South Florida Water Management District spokesman Randy Smith.
“Water flows south from Lake Okeechobee into the Everglades Agricultural Area, then through stormwater treatment areas and into Everglades National Park,” Smith said. “On the very, very rare occasion when stormwater warrants it, pumps might be turned on to provide flood prevention for residents of the communities, but it is not common practice, and it is not part of maintaining water levels on the EAA,” Smith said.
To blame farming for the lake’s glyphosate loads is a mistake, he said.
“I’ll go back 20 years to when I started, when the (district’s) governing board said ‘You will not use those pumps ever unless there is a threat to human safety and life in the surrounding communities due to high water levels.’”