Recent findings from the University of Georgia’s Odum School of Ecology and Marine Extension and Georgia Sea Grant indicate there may be increased quantities of mercury in the waters of Georgia and South Carolina.

Through examining alligators from the Okefenokee Swamp, Jekyll Island, and Yawkey Wildlife Center, UGA researchers detected significant mercury levels, raising alarms about the heavy metal’s presence in the environment.

“Alligators are very ancient beings, and we can observe them in these regions as a signal of what else might be occurring in the ecosystem. Researching them can relate to various aspects of the food web,” stated Kristen Zemaitis, lead author of the study and a graduate of the Odum School.

The presence of mercury in these waters not only affects the well-being of the alligators but may also pose serious health risks to other species depending on these waterways for nutrition, including humans.

Mercury levels are significant for the overall ecosystem

Trace amounts of mercury, a potentially hazardous substance, are frequently detected in runoff and precipitation flowing from major industrial zones. Prior studies have demonstrated accumulating heavy metal levels in smaller creatures in Georgia swamps, though less is known about organisms higher up in the food chain, like alligators.

By analyzing dietary habits and blood samples from over 100 alligators over several months, researchers found that the location of the alligators significantly impacted findings.

Alligators residing in the Okefenokee Swamp exhibited mercury concentrations that were eight times greater than those observed in the other two research locations.

If (mercury) accumulates, it traverses the food web and engenders a perfect storm. That’s the situation we’re facing in the Okefenokee.” —Jeb Byers, Odum School of Ecology

“That’s one of the findings from the study that struck me the most,” remarked Jeb Byers, co-author of the study and UGA Athletic Association Professor in the Odum School. “Mercury is a neurotoxin that is extremely harmful to organisms. If it accumulates, it traverses the food web and creates a perfect storm. That’s the situation we’re facing in the Okefenokee.”

Mercury levels in alligators demonstrate that the toxin can easily ascend the food chain.

Whether it’s the alligators themselves or the fish with which they share their habitat, this study serves as a warning for any humans who may fish or hunt in the vicinity. Although the Okefenokee Swamp is a wildlife refuge, it shares waterways with the Suwannee and St. Marys rivers, which indicates a potentially increased risk of mercury contamination in fish and other wildlife inhabiting those waters.

“Mercury contamination can be a serious concern for those who may consume large quantities of fish or game species from rivers, swamps, or oceans that are high in mercury. In any ecosystem, there are organisms that can only tolerate minimal amounts of mercury, which can lead to neurological issues, reproductive complications, and ultimately mortality,” Zemaitis noted.

The age of alligators is crucial in mercury analysis

It wasn’t solely the habitats of the alligators — the duration of their residence was also significant.

The researchers found that mercury concentrations were higher in larger, older alligators. This was not only due to prolonged exposure but likely because these alligators consumed more contaminated prey over time.

“Organisms can accumulate dangerous levels over their lifetimes. However, we often take age into account but not diet,” explained Benjamin Parrott, an associate professor at UGA’s Savannah River Ecology Laboratory and Odum School, and co-author of the study. “What our research indicates is that as alligators grow and begin to consume larger prey, this amplifies the amount of mercury they accumulate.”

Concerning younger alligators and hatchlings, the results were surprisingly similar. Mercury levels appeared to be inherited by their offspring.

“Some of the hatchlings exhibited exceptionally high mercury levels, which we did not anticipate. Mothers are transmitting toxins and heavy metals into the egg yolks during the reproductive process,” Zemaitis remarked.

Research highlights the necessity for future investigations on mercury effects

It seems likely that high mercury levels in the environment are not only affecting alligators, Zemaitis emphasized.

“Now that we are aware of this issue concerning one of the top predators in these ecosystems, we wonder what else may be impacted?” she said. “I would like to delve deeper into the origins of the mercury and how it enters the ecosystem. It would be very beneficial to pinpoint a major source and determine its effects on other species within the ecosystem.”

The study was supported by the Jekyll Island Authority and the Okefenokee Swamp Park, with contributions from co-authors Thomas Rainwater, of the Tom Yawkey Wildlife Center and Clemson University; Yank Moore, of the Conservation for Jekyll Island Authority; and Kimberly Andrews, a coastal ecology expert with UGA Marine Extension and Georgia Sea Grant.

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