• Posted June 29, 2025

Toxic Mercury in Gators Is a Warning Sign for Other Species

The swamps of Georgia and South Carolina harbor something more dangerous than the alligators for which they’re best known.

Researchers studying the ancient reptiles found high levels of mercury, a potent neurotoxin. Their discovery — reported in the June issue of the journal Environmental Toxicology and Chemistry — not only affects alligators but also endangers other creatures, including people, who rely on these waterways for food.

"We can look at [alligators] in these areas as an indicator of what else might be happening in the ecosystem," said lead researcher Kristen Zemaitis, a biologist at the University of Georgia’s Odum School of Ecology.

UGA researchers studied alligators from the Okefenokee Swamp and Jekyll Island in Georgia and at the Yawkey Wildlife Center on the South Carolina coast. 

Samples of more than 100 alligators collected over several months found the highest levels in gators from the Okefenokee, in Georgia’s southeastern corner. In fact, their levels were eight times higher than those from the other two sites.

"That’s one of the results from the study that was most striking to me," said co-author Jeb Byers, an associate dean at the Odum school. 

"Mercury is a neurotoxin that is very lethal to organisms." he told Science Daily. "If it builds up, it moves through the food web and creates the perfect storm. That’s what we have in the Okefenokee."

The high concentrations in gators are evidence that the toxin can easily move up the food chain — whether it be alligators themselves or the fish they live with and eat and even to people who may rely on the waters for food.

The Okefenokee Swamp is a wildlife refuge, which shares water with two rivers: The Suwannee and St. Marys. As such, those waters and the wildlife living in them are also at risk.

"Mercury contamination can be a high concern for the people who can be consuming a lot of fish or game species from the rivers, swamps or oceans that have high mercury," Zemaitis said. "In any given ecosystem, there are some organisms that can tolerate only very little amounts of mercury, which can result in neurological issues, reproductive issues and eventually death."

Researchers found that how long the alligators had lived in a waterway was important, Science Daily noted.

Bigger, older gators had higher mercury levels, probably from consuming greater amounts of contaminated food over the course of their lives.

"Organisms can accumulate dangerous levels over the course of a lifespan," said study co-author Benjamin Parrott, an associate professor at UGA’s Savannah River Ecology Laboratory. "As alligators grow and start to eat larger animals, this increases the amount of mercury they accumulate."

Even among younger gators and hatchlings, mercury levels were surprisingly high, researchers found.

"Mothers are passing toxins and heavy metals into the egg yolks during reproduction," Zemaitis said.

Researchers now wonder what else is being affected by the contamination.

"I would like to investigate more about where exactly the mercury is coming from and how it’s getting into the ecosystem," Zemaitis said. "It would be really great to pinpoint a prominent source and also see how it’s affecting other animals in the ecosystem."

More information

The Cleveland Clinic has more about mercury poisoning.

SOURCE: Science Daily, June 12, 2025