If you are ever fortunate enough to be driving down Alligator Alley an hour before sunset, you’ll discover that it seems as if Claude Monet painted everything above the sawgrass. The pinks and purples are astonishing, the green is vibrant and the water is crystalline.
But among all this is one of the most dangerous pollutants in the Everglades — mercury.
The 2020 South Florida Environmental Report, published by the South Florida Water Management District, indicated levels of mercury in different species of fish and wildlife that were in some cases far higher than EPA standards allow. American alligators, softshell turtles, white-tailed deer and the endangered Florida panther are some of the animals that have been reported to show elevated levels.
“Mercury is called a global pollutant,” said Yong Cai, department chair of chemistry and biochemistry at Florida International University and a 25-year Everglades researcher. “It can transport a long distance before it precipitates.”
Mercury enters the atmosphere when it evaporates into the air. This can happen through the combustion of fossil fuels, gold mining and the disposal of fluorescent lamps.
When mercury comes in contact with the water in the Everglades, it goes through a series of long and complex microbial processes that eventually turn it into methylmercury.
Methylmercury, a neurotoxin, accumulates in the food chain, increasing in concentration as it goes up. It is the reason why many physicians recommend limiting fish consumption.
“[The Everglades] has a lot of wet ‘depositions,’ meaning a lot of rain and the water properties make it a good environment for inorganic mercury to be methylated,” said Cai.
According to the report, elevated mercury concentrations in fish and plant life have been of concern to scientists since the 1970s. Reported levels of methylmercury in fish were four times the EPA recommended amount in 1989.
Concern reached its peak when a Florida panther was reportedly killed by mercury poisoning.
Restoration, not preservation, is the tactic scientists are using to diminish the pollutants that get into the Everglades.
“It’s been an age-old discussion between preservationists and conservationists about how we should use the environment,” said Robert Shuford, a lead scientist for ecosystem restoration and capital projects.
The big problem in the late ’70s and early ’80s was that gray water — water from toilets, washing machines and runoff — would historically get into the Everglades without being regulated, according to Shuford.
Since then, scientists with the SFWMD have put structures in place to limit the amount of surface runoff that gets into the water.
“Over the last 20 years we have gone from an area that had been getting pretty much pure runoff from surrounding areas to something that was a little more characteristic of the historic Everglades,” said Shuford.
The structures are designed specifically to cleanse the water of phosphorus. This helps in limiting the growth of cattails, which subsequently leads to higher methylation.
However, ridding the water of mercury is much trickier.
“Mercury is already in the environment for a long time and the legacy of mercury is enough for methylation to occur for many years to come,” said Cai. “You can treat the soil, you can treat the air or water, but for a natural environment like the Everglades, there is no way to decontaminate.”
Many countries have signed an international treaty that aims to limit the amount of mercury that is used and exposed to the environment. In 2017, The Minamata Convention on Mercury became effective.
The latest mercury global assessment published by the United Nations noted a modest decrease in mercury emissions as a result of continued action.
Long-term research is still being done to determine if mercury levels are actually falling. Construction of more man-made wetlands to purify Everglades water is expected until 2025.