ALBANY, N.Y. - A crystalline Adirondack lake once held up as an example of a "dead" lake devastated by acid rain has now become a symbol of nature's ability to heal itself once pollutants are curbed.
As the name implies, Brooktrout Lake teemed with trout before air pollution from faraway cities began to change the chemistry of lakes and soils in the 6-million-acre Adirondack Park. In 1984, biologists found that Brooktrout Lake and hundreds of others in the rugged region were completely devoid of fish.
Now there are signs of recovery. After the Clean Air Act amendments of 1990 tightened emissions limits on Midwest coal-burning power plants, acid rain decreased significantly. As expected, the pH levels of Adirondack lakes began to rise, becoming less acidic. The surprising thing was how fast it happened.
"Nobody predicted Brooktrout Lake would come around as fast as it has," said Clifford Siegfried, director of the New York State Museum and a freshwater ecologist who has studied Adirondack lakes since 1984. "Most predictions were for decades of recovery."
Last fall, biologists stocked Brooktrout Lake with 20 adult trout and 2,000 fingerling trout. It was the first time a once-dead Adirondack lake had been restocked with fish after improving enough to sustain fish.
The stocking isn't for the benefit of anglers, but scientists.
"This is a whole lake experiment, an ecological experiment of the highest order," said Charles Boylen, a biologist at Rensselaer Polytechnic Institute's Darrin Fresh Water Institute. He has studied Adirondack lakes since 1994 under a $7 million grant from the Environmental Protection Agency.
"This is a great opportunity to see how nature deals with this phenomenon of acid recovery," he said.
This spring, researchers returned with sonar equipment to see how the fish fared after the snowmelt flooded the lake with a winter's worth of acid deposits. The fish survived. "We're all primed for a productive season," Boylen said.
The researchers will visit the lake every few weeks to observe the fish to see if they reproduce and grow. And they'll monitor the entire ecosystem of the lake to document changes in plankton, algae, plants, insects, loons, salamanders and other species as the natural balance returns.
For ecologists, it will be interesting to watch what happens to the naturally recovering flora and fauna with the introduction of trout, Siegfried said. "These communities have adapted to having no fish for several decades. The top predator is the midge larva," a wriggler the size of an eyelash. "These are nice juicy morsels for trout. They'll likely wipe out that population."
Scientists also will be watching the behavior of a pair of loons that have been nesting on the lake for years. In the past, they've had to go to another lake to feed. Now they'll find trout right at home. "We'll see how that affects fish survival," Siegfried said. "They can eat 1,500 fish annually."
Sampling must be done numerous times over the course of each year because the lake changes significantly from week to week. The acid level is affected by precipitation and temperature, and the abundance of certain organisms rises and falls over short periods.
Collecting samples isn't easy. The trail to Brooktrout Lake is six miles long, and equipment has to be carried in. A state helicopter is sometimes used to make the job easier.
The recovery of Brooktrout Lake may be short-lived, however. Tim Sullivan of E & S Environmental Chemistry in Corvallis, Ore., was contracted by New York state to develop mathematical models that predict what will happen in response to various levels of air pollutant emissions. The outlook isn't good.
"While there has been a substantial decrease in acid deposition, the improvement in lake chemistry has been relatively small," Sullivan said. "If we continue to operate under existing emissions regulations, the lakes that have been recovering will stop recovering and will start to get worse again over the next couple of decades. For some lakes, it will be worse than it ever has been."
That's because soils in the Adirondacks, particularly at higher elevations, have been depleted of calcium and other acid-neutralizing minerals, weakening their ability to serve as a buffer against acid rain, Sullivan said.
To prevent reacidification of the region's most sensitive lakes, such as Brooktrout, further emission controls are needed, he said.
"Recovery is a dangerous word in the hands of politicians. They think the job is done," Boylen said. "But even with more stringent regulations, there's still more consumption of fossil fuels than in years past. If we don't learn to conserve our energy consumption or rely on sources other than fossil fuels, the societal demands will continue to put more and more emissions into the atmosphere."
Darrin Freshwater Institute: http://www.rpi.edu/dept/DFWI/
New York State Museum: http://www.nysm.nysed.gov/