State Water Resources Research Institute Program

Project Id: 2010IL207B
Title: Linking microbial community structure to water quality function: investigating nitrogen cycling during early floodplain development
Project Type: Research
Start Date: 3/01/2010
End Date: 2/28/2011
Congressional District: 15
Focus Categories: Wetlands, Nutrients, Water Quality
Keywords: wetland restoration, denitrification, nutrient cycling, microbiology
Principal Investigators: Kent, Angela; Kent, Angela
Federal Funds: $ 37,662
Non-Federal Matching Funds: $ 76,661
Abstract: Land use change and increased nutrient inputs in combination with wetland losses have exacerbated degradation of Illinois waterways and downstream waters. Floodplain restoration along the Illinois River can potentially mitigate nutrient loading and improve water quality. Microorganisms are responsible for biogeochemical cycling of nutrients, but little is known about the relationship between microbial community composition and ecosystem processes. Further, microbial processes and the populations responsible for microbially-mediated ecosystem functions are influenced by environmental factors that are likely to vary dramatically in response to changes in land use. Understanding the response of microbial communities and their activities to land use change is essential for restoration of wetland water quality functions.

Restoration of the Emiquon Preserve, a floodplain adjacent to the Illinois River, could potentially reduce nutrient (nitrate) export and improve water quality along the Illinois River. Excess nitrates from agricultural runoff can be converted to gaseous forms through the processes of denitrification (NO3- → N2O or N2). Denitrification is an anaerobic process that occurs in saturated soils and sediments. In contrast, nitrification (NH4+ → NO3-) is an aerobic microbial process. Both of these processes are sensitive to oxygen levels, and should be responsive to fluctuations in water levels in the newly restored Thompson Lake at Emiquon. Changes in water saturation of soils will influence oxygen availability in the floodplain sediments, and will affect the balance between nitrification and denitrification processes. Wetland vegetation can introduce oxygen to sediments through their roots, and thus may have some capacity to buffer the rhizosphere environment against extreme fluctuations in oxygen availability. Wetland vegetation may also be an important factor in determining the relative importance of nitrification and denitrification.

We propose to investigate the link between microbial community composition and activity, specifically related to nitrogen cycling, in response to changing water levels in early floodplain development. The proposed research will address the following objectives:

  1. Track changes in nitrogen-specific microbial populations related to denitrification and nitrification along a moisture gradient.
  2. Assess the influence of plants on the relationship between denitrifier and nitrifier populations through comparison of microbial communities associated with rhizosphere soil and bulk soil.
  3. Assess the production of nitrogen gas along a moisture gradient at Emiquon Preserve.

Microbial function will be assessed using denitrification and nitrification assays while microbial community structure will be carried out using "DNA fingerprinting" techniques on the total microbial community, and on specific microbial populations responsible for denitrification and nitrification. Comparison of microbial populations in rhizosphere and bulk soil across a moisture gradient will allow us to determine the capacity of plants to stabilize the soil microbial habitat against fluctuating environmental conditions.

Further understanding of the relationship between microorganisms and their activity in response to changing water regimes can potentially enhance management of this floodplain ecosystem, thus, contributing to the goal of improving quality of Illinois waterways.

Progress/Completion Report, 2010, PDF

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