Water Resources Research Act Program

Details for Project ID 2014IL283B

Year-round wetland microbial activity impacts on nitrogen cycling annual budgets: is restoration impacting greenhouse gas emissions in wetlands?

Institute: Illinois
Year Established: 2014 Start Date: 2014-05-01 End Date: 2014-12-31
Total Federal Funds: $10,000 Total Non-Federal Funds: $20,002

Principal Investigators: Angela Kent

Project Summary: Denitrifying bacterial communities help remove excess nitrate that enters wetlands from agriculture and other human inputs, which if left unprocessed, can end up in downstream ecosystem1. Downstream, nitrate from Illinois rivers can have negative impacts on water quality in coastal zones2. Many studies have shown links between wetland microbial processes, and a decrease in nitrate available to fuel eutrophication downstream, but most of these studies take place during the growing season, usually late spring through the summer1,3. Denitrification rates are high during this period, but substantial denitrification may occur in other seasons, such that point measures or seasonal measures may not be representative ofannual denitrification rates4,5. Furthermore, cold season studies on wastewater treatment wetlands have shown an alarming winter trend that as denitrification rates slow, a greater proportion of nitrate is converted to nitrous oxide, a potent greenhouse gas, than to nitrogen gas, a more innocuous product5,6. Thus, there is a critical need to understand how wetland contributions of greenhouse gases fluctuate over time, and which drivers of microbial activity are implicated in the shift to incomplete denitrification, particularly as we seek to restore millions of acres of wetlands7. My long-term goals include evaluating microbial ecosystem services in a restoration context to ensure establishment of desirable ecosystem functions with minimal contributions to global climate change. My objectives are to determine the seasonal differences in the amount of complete and incomplete denitrification in order to understand wetland greenhouse gas emission rates, specifically focusing on whether seasonal differences are uniform between natural and restored wetlands. Furthermore, understanding the environmental or management factors that may be contributing to complete versus incomplete denitrification is imperative to ensure that wetland restoration is successful in solving water quality issues and simultaneously minimizing impact on climate change. My central hypothesis is that the ratio of complete to incomplete denitrification is influenced by microbial community composition or ecological drivers, including soil factors, or by a combination of both. Our lab has found that denitrification rates are lower in restored wetland sites 8,9, which may influence the amount of nitrate converted to nitrous oxide instead of nitrogen gas. Our rationale is that wetlands are becoming an important part in the restoration landscape, and understanding the underlying processes of the nitrogen cycle, and the ultimate fate of nitrate will help in evaluating possible secondary impacts, including greenhouse gas emissions, of landscape conversions. Our lab has worked extensively with microbial communities in wetlands, especially denitrifier communities. We have a well-established connection with the Illinois Department of Transportation who completes wetland restoration, and have identified appropriate restored sites paired with natural.reference wetland sites. This project would help establish the timing and rates of incomplete and complete denitrification, and whether this is due to the microbial drivers or to environmental variables. This may answer questions about controls on greenhouse gas production in wetlands7,10, and fit into patterns seen in other ecosystems, such as forests where winter months have a large impact on the nitrogen cycle, including nitrous oxide production11.