"The cumulative effects of these different compounds on the biota is not known," Katz said.
Through Ancient Forests
There are an estimated 700 springs in Florida, including 33 "first magnitude" springs, which produce more than 65 million gallons (245 million liters) of water a day.
Springs are particularly vulnerable to contamination because anything that falls onto the ground eventually makes its way into the aquifer, the source of the spring water.
"We're used to thinking of the springs, with their clear water, as a form of beginning, but now we know that the springs are at the end of the pipe, and whatever pressures we place on the landscape in time will flow from the end of the pipe," said Jim Stevenson, a retired official with the Florida Department of Environmental Protection.
Stevenson is now the coordinator of the Ichetucknee Springs Basin Working Group, which draws together government agencies, universities, businesses, and environmental organizations to monitor spring health.
The Ichetucknee, which runs into the Santa Fe River and then joins the Suwannee, is perhaps the most pristine river in northern Florida.
Its shores are lined with old-growth cypress and hardwood forests. Beavers, otters, and manatees can be seen in the waters.
But nitrate levels in its springs are growing and have come to act as an algae fertilizer. In many places along the Ichetucknee, algae can be seen coating native plants and turning the water green.
"The Ichetucknee is dying the death of a thousand cuts with hundreds of new residents a week moving into its springshed," said Annette Long of the advocacy group Save Our Suwannee, based near Chiefland, Florida.
"More residential water wells mean less water for the river and more septic tanks polluting the water that is left."
Scientists agree that the bulk of the state's vast underground repositories of water are still clean.
But Katz, the USGS scientist, says Florida's rapid population growth is a major threat to the environmental health of the Suwannee basin.
"The more Floridians there are, the more polluting chemicals—such as nitrate compounds—hit the ground and get into the water," he said.
"We've found that the older the water in the aquifer, the fewer nitrates are in it," he added. "When you find water that's 50 or 60 years old, there are hardly any nitrates present."
Mercury levels in some fish in the Suwannee River are already among the highest in the southeastern United States. This is partly due to the naturally acidic water in the river, which favors the accumulation of mercury.
Chemicals from personal care products are also of emerging concern.
"There are a lot of opportunities for things like DEET to get into the environment," said Katz. "You apply it, take a shower, and eventually it gets into the ground water system."
Many initiatives from the state to the local level are working to protect the springs.
The state-funded Florida Springs Initiative has committed several million dollars to fund scientific research, water quality studies, and biological monitoring of the springs.
The Suwannee River Partnership is a volunteer program that encourages farmers to adopt practices that help reduce nitrate impacts on groundwater and surface water.
One businessman in Lake City has created the Ichetucknee Promise. In this program, homeowners pledge to reduce the use of lawn fertilizer, have their septic tanks inspected, and write a letter to the local city council and their county commissioner asking that more be done to protect the Ichetucknee.
The promise is sealed with a 50-dollar contribution to fund the construction of drinking water wells in developing countries.
"We can never stop to protect the Florida springs," Stevenson said. "We are going to see more and more people here generating more and more pollution. But we can't give up. These springs are too important."
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