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Microbes in Natural Illinois Wetlands Protect Water Quality

Author: Debra Levey Larson

URBANA - Wetlands are filled with highly diverse plant and animal life that create self-sustaining ecosystems and benefit the overall water quality and environment. But in the past 200 years, due to increasing land development and agriculture, the United States has lost 53 percent of its wetlands and Illinois has lost 90 percent.

"The No Net Loss federal policy was established in 1989 to begin replacing the wetland acreage lost to development," said University of Illinois graduate student in microbial ecology Diana Flanagan. "But, what we learned from looking more carefully at the populations of microbes in Illinois wetlands is that the replacement or constructed wetlands were less effective at providing water quality functions than the natural wetlands."

Flanagan explained that wetland microbes, although tiny organisms, have a great deal of potential to reduce the nutrient pollution from fertilizer run-off into the Mississippi, so that it never reaches the downstream water systems, such as the Gulf of Mexico. Microbes in waterlogged wetland sediments can "breathe" nitrate and transform it into atmospheric nitrogen. This process, known as denitrification, reduces the amount of excess nitrate that flows into downstream ecosystems.

Flanagan and her U of I advisor Angela Kent collected and analyzed soil samples from six pairs of constructed and natural wetlands across Illinois. "Microbial populations all perform different functions in the environment, "said Flanagan. "We wanted to identify the composition of microbes in each of the samples. Although the microbes are all unique, they each have one gene in common. Each group of microbes has a slightly different DNA sequence for this gene, and we were able to use these differences to determine the make-up of the microbial populations in those wetland samples.

"When we compared the activity in the natural wetlands to the constructed wetlands, we found that the differences seen in the denitrification rates were correlated to the pattern seen in the microbial community composition. This suggests that the microbial populations responsible for denitrification have not been restored in the constructed wetlands."

"Denitrification is a microbial process, so it makes sense that composition of the microbial community would impact this process," said Angela Kent, assistant professor in the Department of Natural Resources and Environmental Sciences in the College of Agricultural, Consumer and Environmental Sciences. "Soil microbes are very diverse, however - there can be 5,000 or more different kinds of bacteria in a gram of soil. We were concerned that this diversity was so great that we wouldn't be able to detect the connection between microbial community composition and the denitrification process. Given this diversity, it's also interesting that we saw clear patterns of microbial community composition among natural and constructed wetlands."

Flanagan said that she hopes this information and further research into environmental factors that influence wetland microbes will be used to inform landscape managers, designers and other landowners.

"This work has generated hypotheses about the environmental factors that influence wetland microbes and their activities," said Kent. "Next, we will carry out experiments where we change some environmental factors and observe the impact on wetland microbial communities to determine if our hypotheses are correct. Ultimately, we hope to make recommendations about how to enhance beneficial microbial processes in wetlands."

Funding for this study was provided by the University of Illinois and USDA.

Source: Diana Flanagan, (618-214-6850; dflanaga@uiuc.edu)