HR: 14:45h
AN: NB23E-06 INVITED     [Abstracts]
TI: Factors Controlling Denitrification and NO₃ Uptake in Three Tropical Puerto Rican Streams Using a ¹⁵N Tracer Approach.
AU: * Potter, J D
EM: jody.potter@unh.edu
AF: University of New Hampshire Department of Natural Resources, 215 James Hall, Durham, NH 03824 United States
AU: McDowell, W H
EM: bill.mcdowell@unh.edu
AF: University of New Hampshire Department of Natural Resources, 215 James Hall, Durham, NH 03824 United States
AU: Merriam, J L
EM: jeff.merriam@unh.edu
AF: University of New Hampshire Department of Natural Resources, 215 James Hall, Durham, NH 03824 United States
AU: Thomas, S M
EM: sthomas@mbl.edu
AF: Marine Biological Laboratory Ecosystems Center, 7 MBL Street, Woods Hole, MA 02453 United States
AU: Peterson, B J
EM: peterson@mbl.edu
AF: Marine Biological Laboratory Ecosystems Center, 7 MBL Street, Woods Hole, MA 02453 United States
AB: An intensive study that was part of the LINX II project was conducted to determine nitrogen transformations of 3 low-order streams with contrasting land use. Short term (24-hour) additions of K¹⁵NO₃ and NaBr were performed on forested, urban, and agricultural streams to determine anthropogenic impacts on N retention in tropical streams. Stream water and organic matter samples were collected before, during, and after the experiment. We hypothesized that there would be greater uptake into biomass and higher denitrification (¹⁵NO₃ to ¹⁵N₂ and ¹⁵N₂O) in streams with greater human impacts and stream nitrate concentrations. Background nitrate concentrations ranged from 148 ug N/L in the forested stream to 259 ug N/L in the agricultural stream to 875 ug N/L in the urban stream. Denitrification to ¹⁵N₂ was undetectable in the forest stream, was small in the agricultural stream, and was highest in the urban stream. Denitrification to ¹⁵N₂O was detectable in all 3 streams and followed the same increasing pattern with ambient nitrate concentrations. Incorporation of ¹⁵N into biomass was lowest at the forest stream, intermediate at the agricultural stream, and highest at the urban stream. Nitrate loading associated with change in land use resulted in greater denitrification and uptake in biomass.
DE: 0400 Biogeosciences
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly