Prior to enactment of the U.S. Clean Air Act, unhindered industrial emissions were released into the air across the nation, with many of the chemicals falling back to Earth in the form of acid rain.

Although scientists have long known acid rain can severely decrease the diversity of plant and animal communities in fresh water lakes and ponds, little is known about how microscopic bacteria respond to acidification.

Rensselaer Polytechnic Institute researchers, using their newly created database, have found a general link between increased acidity and decreased bacterial diversity, but with the most dominant species of bacteria not directly impacted by acidification.

However, some rarer types of bacterial populations were significantly or strongly correlated to acidity, rising and falling with fluctuations in water pH. The findings might eventually allow researchers to use those bacteria as indicators of lake recovery, said Professor Sandra Nierzwicki-Bauer, director of the Darrin Fresh Water Institute at Rensselaer.

The study, in partnership with the Skidaway Institute of Oceanography, appeared in a recent edition of the journal Applied and Environmental Microbiology.