HR: 16:15h
AN: NB24F-04    [Abstracts]
TI: Denitrification Rates in Streams Determined in an Intersite ¹⁵N Addition Study
AU: * Mulholland, P J
EM: mulhollandpj@ornl.gov
AF: Oak Ridge National Laboratory, Environmental Sciences, ORNL PO Box 2008, Oak Ridge, TN 37831
AU: Ashkenas, L R
AF: Oregon State University, Dept. of Fisheries and Wildlife Oregon State Univ., Corvallis, OR 97331
AU: Bernot, M J
AF: University of Notre Dame, Dept. of Biological Sciences Univ. of Notre Dame, Notre Dame, IN 46556
AU: Crenshaw, C
AF: University of New Mexico, Dept. of Biology Univ. of New Mexico, Albuquerque, NM 87131
AU: Dahm, C
AF: University of New Mexico, Dept. of Biology Univ. of New Mexico, Albuquerque, NM 87131
AU: Dodds, W K
AF: Kansas State Univ., Div. of Biology Kansas State Univ., Manhattan, KS 66506
AU: Findlay, S
AF: Institute of Ecosystem Studies, Institute of Ecosystem Studies Box AB, Millbrook, NY 12545
AU: Gregory, S
AF: Oregon State University, Dept. of Fisheries and Wildlife Oregon State Univ., Corvallis, OR 97331
AU: Grimm, N B
AF: Arizona State University, Dept. of Biology Arizona State Univ., Tempe, AZ 85287
AU: Hall, R O
AF: University of Wyoming, Dept. of Zoology & Physiology Univ. of Wyoming, Laramie, WY 82071
AU: Hamilton, S
AF: Michigan State University, Kellogg Biological Station Michigan State Univ., Hickory Corners, MI 49060
AU: Johnson, S L
AF: US Forest Service Pacific NW Research Station, USFS PNW Research Station 3200 SW Jeffereson Way, Corvallis, OR 97331
AU: McDowell, W H
AF: University of New Hampshire, Dept. of Natural Resources Univ. of New Hampshire, Durham, NH 03824
AU: Merriam, J L
AF: University of New Hampshire, Dept. of Natural Resources Univ. of New Hampshire, Durham, NH 03824
AU: Peterson, B J
AF: Marine Biological Laboratory, The Ecosystems Center Marine Biological Lab., Woods Hole, MA 02543
AU: Sheibley, R
AF: Arizona State University, Dept. of Biology Arizona State Univ., Tempe, AZ 85287
AU: Tank, J L
AF: University of Notre Dame, Dept. of Biological Sciences Univ. of Notre Dame, Notre Dame, IN 46556
AU: Thomas, S
AF: Marine Biological Laboratory, The Ecosystems Center Marine Biological Lab., Woods Hole, MA 02543
AU: Valett, M
AF: Virginia Tech, Dept. of Biology Virginia Tech, Blacksburg, VA 24061
AU: Webster, J
AF: Virginia Tech, Dept. of Biology Virginia Tech, Blacksburg, VA 24061
AB: Several recent studies have suggested that denitrification in streams may be a significant sink for fixed nitrogen in the landscape. Most previous studies of denitrification have relied on either acetylene block techniques using laboratory sediment core incubations not reflective of in situ conditions or indirect estimates involving changes in streamwater concentrations of nitrate. In this study, we used a new field ¹⁵N tracer addition approach that directly measures in situ rates of denitrification at the scale of entire stream reaches by determining tracer ¹⁵N-nitrate flux into nitrogen gas. We measured denitrification rates in headwater streams in 8 regions across the U.S. draining reference, agricultural, and urbanized catchments. Partial results from the first 2 years of this 3-year study showed denitrification rates ranging from undetectable to 1.1 ug N m^-2 s^-1 and, on average, accounting for about 20% of total nitrate uptake. In general, denitrification rates were higher in urbanized streams than in reference and agricultural streams. Denitrification rates also were positively related to streamwater nitrate concentrations. Results to date indicate that while denitrification is an important sink for nitrate in streams with high nitrate concentrations, it is generally low relative to total loss of nitrate from water.
DE: 0400 Biogeosciences
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly