The Springs in Trouble: What Nitrate Is Doing to Ancient Water

The springs of Marion County are among the oldest tourist destinations in North America, and among the most threatened natural features in Florida. These two facts are connected.

Silver Springs has been flowing for thousands of years. Its water originates as rain, percolates down through the porous limestone of the Floridan Aquifer, and emerges here after a journey that can take decades. The aquifer is vast. What enters it anywhere in a wide catchment area eventually surfaces at the spring vent.

For most of Florida's history, the water entering the aquifer was clean. Then agriculture scaled up. Septic systems proliferated. Fertilizers soaked through the sandy soils and into the rock. Nitrate, a compound from fertilizer and sewage, began accumulating in the aquifer. It does not filter out easily once it is in the limestone.

The results at Silver Springs are measurable and alarming. The spring's flow has declined from historic averages. Nitrate concentrations in the water now far exceed what scientists consider the threshold for plant death, the level above which the eelgrass and other native aquatic vegetation that anchor the spring's ecosystem begin to die off. Algae blooms, fed by the nitrate, replace native plants in exactly the way kudzu replaces native trees on land.

The state of Florida has set legal targets for reducing nitrate. Septic tanks in the Silver Springs basin are being converted to sewer systems. Fertilizer restrictions have been imposed in sensitive zones. Whether these measures will work, and how quickly, is genuinely uncertain.

What is certain is that the glass-bottom boat tourists who have come here since the eighteen seventies have been looking at something that took thousands of years to form. The aquifer that makes it possible does not repair itself on a human timeline.