Brooktrout Lake, located in the Adirondack Mountains near Speculator, N.Y., was once a crystalline body of water that had become a textbook example of a dead lake caused by acid rain. The 1990 Clean Air Act amendments tightened emission limits on coal-burning power plants in the Midwest and acid rain events significantly diminished. Since then, pH levels of lakes located in the Adirondacks have rebounded much quicker than originally predicted.

“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.”

While still not ready for fishing, the state did stock the lake with adult and fingerling trout last fall. Examinations this spring determined that the fish had survived the winter. State biologists said they look forward to watching how the wildlife reacts to the positive changes.

Not everyone was as optimistic. Some consultants predicted the changes were the results of several acid-neutralizing minerals that were naturally occurring at the higher elevation, and once such stores were depleted, the problem would return if additional emission controls were not put in place.