1. JAEL EDGERTON KENT STATE UNIVERSITY Effects of Labile Carbon Addition on Denitrification and Denitrifiers in a Headwater Agricultural Stream

2. Anthropogenic Changes to the Global N-Cycle Human activities - increased inputs of fixed nitrogen Nitrogenous fertilizer runoff- Eutrophication Hypoxia Deadzone formatio n. Microbial Denitrification – stepwise reduction of NO 3 to N 2 by facultative anaerobes Denitrification –returns biovailable N can to the atmosphere.

3. Labile Carbon Additions to a Midwestern Agricultural Stream 1. How tightly coupled are DOC and N cycling? 2. How does denitrification in an agricultural stream respond to changes in the pool of DOC? 3. Is the response mediated through changes in the microbial community? Formate:acetate coupled with 15-N tracer Whole stream uptake of C and N, and denitrification rate Microbial community structure Sensor technology -chemical and physical variables in the water column

4. Results Effectively shifted the carbon dynamics of the stream Increased N-demand via assimilatory mechanisms Did not effect denitrification rate Shifted the overall microbial community (as demonstrated by 16S rRNA gene TRFLP profiles) Assimilatory N-Uptake and Denitrification Figure credit: Todd V. Royer

5. Why wasn’t Denitrification Affected? Figure credit: Todd V. Royer

6. Future Directions Location—sediment level, reducing conditions, hypoxia Scale- centimeter scale, millimeter scale, micrometer scale R.L. Meyer et al. (2008). Marine Chemistry 110, 68–76.