Florida’s new state budget includes millions for invasive aquatic plant management, like a collective $3.2 million to reduce unwanted vegetation in Lake Tohopekaliga and East Lake Toho in Osceola County. Both those lakes, like most in Central Florida, are polluted enough to fail state and federal water quality standards, according to the Environmental Protection Agency.
In fact, Florida ranks first for how many acres of its lakes are classified as “impaired” for swimming and aquatic life: 80%, according to the Environmental Integrity Project.
At Lakes Toho, mercury and high concentrations of the nutrients nitrogen and phosphorus are polluting the water. At Lake Apopka in Orange County, nitrogen and phosphorus are also a problem, along with pesticides found in fish tissue.
Those chemical pesticides, used to treat invasive plants like the underwater plant hydrilla, are what longtime angler Scott Wilson is worried about. He and many other anglers and outdoor enthusiasts say the chemicals are doing more damage to Florida waters than the invasive plants themselves.
“I've seen lakes go from some of the most phenomenal, unknown bass fisheries on the planet to being absolutely mud pit within the matter of one or two years of constant [herbicide] spraying,” Wilson said from his small fishing boat on Orange Lake, in Marion and Alachua counties.
Lately, bass fishing here at Orange Lake is actually doing quite well, according to data from the Florida Fish and Wildlife Conservation Commission. Wilson thinks it’s one of only a handful of good fisheries left in the state.
“I'm watching my Florida die,” Wilson said from his small fishing boat on Orange Lake, in Marion and Alachua counties. “I could break down and cry right now … I’ve watched my lakes get destroyed, one by one.”
The chemicals
Of the roughly 400 pesticides currently registered with the EPA, only 17 are authorized for use in Florida waters, and experts say they undergo rigorous testing before and after being approved.
But since most testing is done by the manufacturers of the pesticides in controlled laboratory settings, long-term, reliable data about the impacts of chronic pesticide use over time is “few and far between,” according to Alexis Temkin, a senior toxicologist with the Environmental Working Group.
“When pesticides get out into the real world, as they often do … those real-world exposure scenarios can often lead to very different results,” Temkin said.
Generally, toxicity studies in labs are done at very high concentrations; for instance, one study might look at how much of a pesticide is necessary to kill a certain type of fish. But in the real world, lower concentrations of that pesticide might be associated with other, more subtle health impacts, like reproductive or developmental challenges, Temkin said.
Although pesticides are certainly studied in academic and independent research, that research is “rarely considered or given as much weight as the studies that the manufacturers themselves are submitting,” to the EPA, Temkin said.
“Often, that data is just not integrated into risk assessments for pesticides in a really meaningful way,” Temkin said. “So there’s always this catch-up.”
Although pesticides and PFAS, or “forever chemicals,” aren’t necessarily one and the same, some pesticides do include PFAS: usually as “inert” ingredients, which help the pesticide’s primary, or “active,” ingredient do its job, like by stopping it from caking or foaming. But some “active” pesticide ingredients do meet the technical definition for PFAS, which might help explain growing evidence of pesticides spreading more PFAS than previously thought.
“You can only make the best decisions with the best data that you have,” Temkin said.
In Florida, decisions are made carefully about which herbicide to use and where, according to Jason Ferrell, director of the Center for Aquatic and Invasive Plants at the University of Florida Institute for Food and Agricultural Sciences.
It’s all about what Ferrell calls herbicide selectivity: “How do you select the plants you want to manage and then not do harm to the others?”
“The risk is never zero, for anything we're putting into the environment,” Ferrell said. “But because of the tremendous amount of science and research that goes into registration and pesticide use, the risk is very, very low, and often well below the risk of allowing these invasive plants to continue to breed and expand across our landscape.”
The plant
Hydrilla is a non-native, underwater plant that can create some serious risks for lake ecosystems, but in moderation, it can also provide some ecosystem benefits.
The challenge is actually reaching that ideal point of moderation with hydrilla, which grows incredibly fast: up to 191 inches a day for a single plant, Ferrell said. As it approaches the lake surface, hydrilla spreads out wide, often blocking other, native plants from sunlight.
But hydrilla can also be a great fish habitat and an effective water filtration mechanism, used to clean water in some of the state’s stormwater treatment areas. The plant’s pros and cons demonstrate how tough it can be to create a treatment strategy for a given species.
“How do you select the plants you want to manage and then not do harm to the others?” Ferrell said. “That is why these decisions are so nuanced and so difficult.”
Hydrilla in itself is not inherently bad, just a difficult plant to control.
“If you don't have any other submersed plants, hydrilla is better than nothing,” Ferrell said. “Hydrilla is not a nasty, terrible plant. But it is a plant that can do nasty, terrible things.”
Because it spreads so quickly, hydrilla can create severe flood risk by clogging up key waterways, including canals that water regulators drain to avoid overflow during heavy rainfall events. For example, it’s especially critical to keep hydrilla from blocking Lake Apopka’s single relief valve, the Apopka-Beauclair Canal, according to the St. Johns River Water Management District.
Additionally, when hydrilla shade kills other aquatic plants, those plants decay, putting more nutrients in the water and collecting into muck at the bottom of the lake. Although muck in itself isn’t bad, according to UF/IFAS, too much of it will rot, breeding low oxygen conditions and more of the nutrients plaguing Central Florida lakes.
Using a four-foot fishing net, Wilson scooped out some of the dark, smelly muck material oozing up from the bottom of Orange Lake: “Absolute chocolate milk.”
Just like other, native aquatic plants, hydrilla also decays when it dies, ultimately turning into muck. Florida treated more than 26,000 acres of hydrilla in fiscal year 2022-23, mostly with chemical herbicides.
Wilson and many others in Central Florida say they’d rather keep more hydrilla alive than rely on aggressive herbicide treatments to control its spread.
“It is not going away, so we’ve got to get smart enough to use it,” Wilson said. “It's there. All we gotta do is quit spraying it, allow it to grow and then mechanically harvest it.”
FWC says mechanical treatments aren’t as cost-effective as chemical ones, but to some extent, the jury is still out. Recently-published findings from a 2022 study suggest mechanical harvesting might be most effective as a tool used at only very specific sites, although that study focused on harvesting water hyacinth, not hydrilla.
One thing is for sure: Central Florida’s lakes and other freshwater resources aren’t healthy. Wilson says it’s past time to solve that problem.
“Every Floridian depends on clean water,” Wilson said. “The complete degradation of every freshwater body in Florida is gonna eventually, in the near future, touch every pocketbook in this state.”
