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Acid rain pushes lakes to the brink

Once pristine Lake Annie is showing the effects of Florida's power plants, incinerators and traffic jams miles and miles away. Carried by the wind, sulfuric acid and other chemicals from burned fossil fuels are altering the rural lake west of Lake Okeechobee and hundreds of other bodies of water across Florida.

The exact nature of the changes remains to be seen, but scientists are gathered in Tampa for three days to share information collected while they track acid rain's effects on Florida.

Once described as an environmental hazard largely confined to portions of Canada and New England, the evidence is well-documented that acid rain pollutants continue to enter Florida's lakes and streams, including Lake Annie, west of Lake Okeechobee.

"Perhaps this is a very significant time for lakes like Lake Annie," said Edgar Lowe, director of environmental sciences for the St. Johns Water Management District.

Lowe has a particularly good grasp of Lake Annie's changing conditions because of a unique convergence of circumstances that makes the 91-acre lake a very unusual, if very unlikely, acid-rain laboratory.

"Lake Annie is a window into the past as well as into the aquifer" from which most Floridians get their drinking water, Lowe said after his

presentation Tuesday.

The lake is in central Highlands County, on the sprawling property owned by the Archbold Biological Station, one of Florida's oldest, most respected scientific research institutions. Archbold was founded in the 1930s by a New York philanthropist so researchers could study Florida's unique scrub habitat, which today holds dozens of threatened and endangered plant and animal species.

Seemingly protected from mankind's intrusion, Lake Annie's waters have instead become more and more acidic over the years.

Lowe and his research staff know this because one of his top scientists, Lawrence Battoe, has tested Lake Annie's waters for long-term changes since he was a graduate student in the mid-1960s. And for 10 years before that, the U.S. Geological Survey had taken occasional samples, making the lake one of the most carefully evaluated during a relatively long period in fast-growing Florida.

The research has also underscored Lake Annie's uniqueness. Scientists know that the lake is about 44,000 years old, far older than many Florida lakes, especially its clear ones. The lake relies on the shallow aquifer, rather than direct rainfall, for about 90 percent of its water. The 300 feet of sand beneath the lake readily transports the ground water and any contaminants the water holds directly into and out of the lake.

The long-term sampling has clearly shown that the lake has become more acidic, especially since the 1970s, when the pace began to quicken.

Lowe said a comprehensive biological evaluation of the lake's plant and animal species must still be undertaken to see what, if any, changes have been wrought on life forms.

But biological research already conducted in a number of acidic North Central and Panhandle Florida lakes has shown that Lake Annie is teetering on the edge of change.

Dan Canfield, a University of Florida researcher, described Tuesday how largemouth bass stocked into two especially acidic North Florida lakes simply have not reproduced, even though they are sexually mature, function properly and build nesting beds.

"We have yet to find a young bass in those lakes," Canfield said. "Why they are not reproducing, we don't know."

At the same time, a common gamefish species known as the shellcracker or red ear, is not found in lakes as acidic as Lake Annie has become.

"Acidic lakes tend to have reduced species abundance and biomass, just like up North" in New England and Canada. As did most of his colleagues, Canfield added that much work remains before researchers can clearly trace the intricate relationships in and around Florida lakes and the effects created by acid rainfall.

As if Lowe and his researchers didn't already have enough on their hands, he described another chronic pollution problem that, as elsewhere in Florida, has befallen Lake Annie: "Levels of mercury in bass taken from Lake Annie are well above the 0.5 parts per million that's considered the safe limit" for human consumption. "It has one of the highest (mercury) levels in the state."