Study finds nitrates not only problem affecting springs
By Cindy Swirko
Reduction of nitrate-rich fertilizer and septic system waste alone will not stem the growth of unwanted algae that is fouling Florida’s springs, while the velocity of water bubbling from the aquifer has a greater role in spring health than believed.
Those are the primary findings of a new springs study by the St. Johns River Water Management District and the University of Florida, and they are a bit of a surprise to some, including Dean Dobberfuhl, SJRWMD water resources bureau chief.
“I thought nitrate would be more important than it turned out to be,” Dobberfuhl said. “But we also knew there were numerous things that control the springs, so while we thought nitrate would be more important, it didn’t necessarily surprise me that there are other important drivers in the system.”
Florida’s springs — openings of the vast underground Floridan aquifer — are cultural treasures, enormously popular recreation spots, economic boosts and complex ecological webs of water, sunlight, plants and animals.
But the springs are increasingly imperiled, which makes them a battleground between environmentalists and business groups such as Associated Industries of Florida, the Florida Fertilizer and Agrichemical Association and the Florida Chamber of Commerce.
The study — the Collaborative Research Initiative on Sustainability and Protection of Springs, or CRISPS — began in 2014 to better understand the influence of natural and human-caused factors on the health of springs.
For UF, the Institute of Food and Agricultural Sciences and the Water Institute joined in the study.
Silver Springs in Ocala and Alexander Springs in the Ocala National Forest were studied, but many of the findings can be applied to springs in general.
Springs are increasingly filled with thick filaments of algae that will grow on aquatic grass, rocks, the spring floor and anything else to which it can anchor. The algae does not substantially contribute to the diet of other spring life such as snails and turtles, and it ugly.
Scientists wanted to learn if reducing nitrates alone can reduce the algae and improve the health of the spring. The study found it will not.
Instead, other factors, including water flow, have a major impact in the growth of algae on the aquatic grasses that are so vital to the ecosystem.
Faster water results in less algae growth on plants by curbing initial colonization and by sweeping away some of the algae that did grow.
David Kaplan, an assistant professor in UF’s Department of Environmental Engineering Sciences, said part of the research involved putting a piece of plastic in a part of the Silver River to block water flow.
“Those plants stopped waving around underwater and stood up because the water was still. Within a week they were 100 percent coated in algae,” Kaplan said. “Next door, the grass was waving around. Where we didn’t block the flow, the algae didn’t accumulate. And when we took that plastic away and let the flow go back through, the algae within a day went back to background levels.”
The study points the need for understanding the entire spring system to find the best moves for protecting them.
Environmentalists and springs advocates said the role of water velocity slow the rate of water withdrawals from the aquifer by municipal systems, residential growth, agriculture and industry.
Eric Hutcheson has been diving in Florida’s springs for decades and has witnessed a reduction in flow over the years. While other factors such as drought can affect it, Hutcheson believes too much pumping is the culprit.
“If you got in a helicopter and flew 3,000 feet straight up from Silver Springs, you could see the Villages, On Top of The World — all of the major developments of this area,” Hutcheson said. “It’s real simple — the rise of these developments, the fall of our water flow.”
Jim Gross, executive director of Florida Defenders of the Environment, said the study provides data that should be used by the district when considering whether to grant water use permits.
“I think they will but maybe not in the near term,” Gross said. “It just depends on what kind of leadership we have in Tallahassee.”
Casey Fitzgerald of the district’s water and land resource bureau said the findings will be discussed at a UF Water Institute symposium next month.
An analysis showed pumping was a minimal impact on the flow of Silver Springs, Fitzgerald said. The major factors were dought and damming.
“There has been an explosion of vegetation that is backing up and putting pressure on the springhead so there is less flow,” Fitzgerald said. “We are looking at options to remove some of that vegetation including a more aggressive campaign against invasion exotics like hydrilla…and to reroute some flow to get more velocity into the system.”
He added that efforts to reduce nitrates from getting in the aquifer should continue.
Whatever action is eventually taken, Kaplan said the study should continue to build on the foundation of CRISPS and learn whether the action has been effective.