HR: 11:45h
AN: NB22E-06    [Abstracts]
TI: Denitrification in Agriculturally Influenced Coastal Plain Streams
AU: * McMillan, S K
EM: smcmillan@unc.edu
AF: University of North Carolina at Chapel Hill, Institute of Marine Sciences, 3431 Arendell St, Morehead City, NC 28557 United States
AU: Ensign, S H
EM: ensign@email.unc.edu
AF: University of North Carolina at Chapel Hill, Institute of Marine Sciences, 3431 Arendell St, Morehead City, NC 28557 United States
AU: Thompson, S P
EM: sthompso@email.unc.edu
AF: University of North Carolina at Chapel Hill, Institute of Marine Sciences, 3431 Arendell St, Morehead City, NC 28557 United States
AU: Paerl, H W
EM: hpaerl@email.unc.edu
AF: University of North Carolina at Chapel Hill, Institute of Marine Sciences, 3431 Arendell St, Morehead City, NC 28557 United States
AU: Piehler, M F
EM: mpiehler@email.unc.edu
AF: University of North Carolina at Chapel Hill, Institute of Marine Sciences, 3431 Arendell St, Morehead City, NC 28557 United States
AB: Agricultural runoff from coastal plain watersheds contributes nitrogen to downstream estuarine and coastal waters. Nitrogen fuels eutrophication, which has resulted in increased algal biomass, hypoxia, and fish kills in the Neuse River Estuary, North Carolina. Denitrification is the sole mechanism of permanent nitrogen removal along the riverine to estuarine continuum, but its contribution to nitrogen attenuation in this system is not well understood. Denitrification rates measured seasonally in stream bed sediments were variable but showed a distinct spring maximum, which was likely associated with rising temperatures and added nitrogen from fertilizer application (0-150 umol N m^-2 h^-1 during the summer, fall and winter and 150-300 umol N m^-2 h^-1 in the spring). Reach-scale uptake experiments showed the potential for 65-98% retention of the watershed DIN load in ephemeral drainage ditches. Results indicated that nitrogen retention was high despite low hyporheic exchange that is typically associated with channelized streams with low gradients, straight channels and homogenous stream bed sediments. Comparison of direct denitrification rate measurements to reach scale uptake rates and a watershed mass balance showed considerable potential for nitrogen removal via denitrification in agricultural stream sediments.
DE: 0400 Biogeosciences
DE: 1860 Runoff and streamflow
DE: 1871 Surface water quality
DE: 9902 NABS Student Award Applied Research
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly