Manatees, aka sea cows, are so iconic to Florida, that the state even has one county named after these gentle, endangered marine mammals. 

The numbers of surviving manatees along the Florida coast has increased significantly since a 1991 aerial survey estimated less than 1,300 left. Roughly five years ago, there were over 6,300 manatees spotted. That’s the good news for manatees and those who love them. The bad news is that since the start of 2021, more than 539 of them have died in Florida waters. Red tides, boat collisions, and habitat loss are the greatest threats to the survival of Trichechus manatus, says Fort Myers News Press. 

But a recent study published in Environment International adds one more challenge for the beloved sea creatures: the controversial herbicide, glyphosate. 

Best known as the active ingredient in Monsanto’s Roundup weed killer, glyphosate has been at the center of over 125,000 suits filed. Plaintiffs who filed claims against Monsanto allege that they developed a rare form of cancer, non-Hodgkin’s lymphoma, because of long-term exposure to the herbicide and its inert ingredients.

Last year, Bayer AG, which acquired Monsanto for roughly $63 billion, agreed to settle the majority of the lawsuits for over $10 billion. Despite the staggering settlement, which does not include another $2 billion Bayer has proposed for resolving any future Roundup cancer claims, glyphosate and Roundup are declared safe to use by the US Environmental Protection Agency (EPA). 

Fort Myers News Press says glyphosate is ubiquitous in Florida waters; the controversial substance is “one of the go-to weapons in land managers’ and homeowners’ arsenals for combatting [sic] weeds.”

Although a direct link between the deaths and glyphosate has not been established, “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,” Pat Rose, Save the Manatee Club director, wrote in an email to Fort Myers News Press.

The study found that glyphosate was detected in the plasma of nearly 56% of the manatees tested. Moreover, concentrations of the herbicide (glyphosate is also registered by the EPA as a pesticide) were found to have increased in manatee blood between 2009 and 2019. 

Lab animals exposed to the same level of glyphosate as the manatees have developed kidney and liver damage. 

Chronic exposure to glyphosate in Florida waterways could impact the endangered marine mammals’ immune and renal systems. Manatee health is already compromised by the stress caused by environmental factors, such as harmful algal blooms; glyphosate, theoretically, could be pouring salt on the wound. 

“Manatees are Exhibit A that Florida’s waters are in crisis and they shouldn’t be facing this kind of pesticide threat,” Jaclyn Lopez, Florida director of the Center for Biological Diversity wrote in a statement, per Fort Myers News Press. 

Lopez added, “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.”

In 2015, the World Health Organization’s International Agency for Research on Cancer declared glyphosate a probable carcinogen to humans. But that agency is the only one to make such a declaration. The EPA maintains that glyphosate is safe when used as directed, even though the agency late last year issued a report that suggested the herbicide poses a risk to endangered plant and animal species.  

In addition to the potential threat caused by glyphosate residue in the body of all mammals, the herbicide may kill aquatic plants like seagrasses that manatees feed on. Furthermore, environmental advocates maintain that glyphostae may itself be the cause of harmful algae blooms. 

The study was funded by “For Everglades Foundation and Fulbright Commission (Uruguay-U.S.) (and) the College of Veterinary Medicine of the University of Florida,” the authors write in the acknowledgements. To read the full article in Fort Myers News Press, click here.