Many of the harmful chemicals that are released into the atmosphere from industrial emissions, come right back down to Earth in the form of acid rain, a chemical concoction that includes nitric and sulfuric acid.
Researchers have long known that acid rain can severely decrease the diversity of plant and animal communities in fresh water lakes and ponds.
However, little is known about how microscopic bacteria, which form the foundation of freshwater ecosystems, respond to acidification.
To address this knowledge gap, researchers at the Darrin Fresh Water Institute of Rensselaer Polytechnic Institute have developed a broad database on the impacts of acid rain at the foundation of the biological community.
The team found a general link between increased acidity and decreased bacterial diversity, but surprisingly, most of the dominant species of bacteria were 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.
According to Sandra Nierzwicki-Bauer, director of the Darrin Fresh Water Institute and professor of biology, the findings could eventually allow scientists to use these bacteria as indicators of lake recovery.
The research is part of a much broader study on how Adirondack lakes in the US are recovering from the impacts of acidification.
For the study, 31 physical and chemical parameters were examined for each water body, ranging from water clarity and temperature to aluminum and hydraulic retention time for a one-year period.
Clone "libraries" representing the bacteria were developed from the lake samples and analyzed.
The researchers found that the species diversity in acid-impacted Adirondack lakes were similar to bacterial communities in other, non-impacted freshwater systems.
The impacts of acidity on most types of bacteria, including the freshwater classes of Actinobacteria and Betaproteobacteria, were found to be indirect, and population levels appeared more directly linked to a combination of acidity along with other environmental factors such as lake depth and carbon content.
Several less abundant types of bacteria, including a species known as Alphaproteobacteria, were strongly correlated to acidity and might someday be used as indicators of lake recovery from acidification, according to Nierzwicki-Bauer.
"I hope this study will help other scientists expand on the research and use this data to uncover additional information on how acid-impacted lakes and their ecosystems are recovering and how we can hasten that process," she added.