PARENT SESSION
Organized Oral Session 44: Linking the practice of stream restoration with the science of stream ecology
Organizer(s): PM Mayer, J Williams, and S Kaushal
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 511 C, Level 5, Palais des congrès de Montréal
Ecosystem restoration and denitrification in an urbanizing watershed of the Mid-Atlantic U.S.
Kaushal, Sujay*,1, Groffman, Peter2, 1 University of Maryland Center for Environmental Science, Frostburg, Maryland, USA2 Institute of Ecosystem Studies, Millbrook, New York, USA
ABSTRACT- Substantial removal of nitrate can occur in the hyporheic zone of streams, but this process may be impaired in urbanizing watersheds due to alterations in hydrology and the transport of nutrients. We tested whether geomorphic restoration of streams could increase rates of denitrification in a coastal watershed draining into the Chesapeake Bay using an in situ 15N tracer technique. Throughout seasons, rates of denitrification in hyporheic wells were spatially variable across sites and ranged from undetectable levels to greater than 200 micrograms of N/kg sediment/day. Rates of denitrification were significantly greater in the restored reach of the stream as compared to the unrestored reach. In the restored reach, sandy riparian areas designed for frequent overland flooding showed higher rates of denitrification as compared to vegetated riparian areas designed for less flooding. Higher rates of denitrification in the restored reach coincided with significantly lower concentrations of nitrate in hyporheic ground water. Spatial patterns in denitrification were consistent seasonally, but rates of denitrification appeared to increase over time following restoration. Denitrification in the hyporheic zone of streams can represent a considerable loss of nitrogen, which has been previously difficult to quantify. Geomorphic restoration of stream channels and hyporheic zones may have the potential to significantly reduce the amount of N delivered to coastal waters.
Key words: streams, restoration, denitrification, hyporheic zone