HR: 1330h
AN: NB33L-07    [Abstracts]
TI: Nitrogen dynamics and foodweb interactions in two contrasting Arctic streams
AU: * Wilcox, H
EM: hwilcox@mbl.edu
AF: The Ecosytems Center Marine Biologiacl Laboratory, 7 MBL ST, Woods Hole, ma 02543
AU: Sanzone, D M
AF: National Parks Service, 201 First Avenue, Fairbanks, Ak 99701
AU: Peterson, B J
AF: The Ecosytems Center Marine Biologiacl Laboratory, 7 MBL ST, Woods Hole, ma 02543
AU: Benstead, J P
AF: The Ecosytems Center Marine Biologiacl Laboratory, 7 MBL ST, Woods Hole, ma 02543
AU: Deegan, L A
AF: The Ecosytems Center Marine Biologiacl Laboratory, 7 MBL ST, Woods Hole, ma 02543
AU: Bowden, W B
AF: University of Vermont Rubenstein School of Environment & Natural Resources , 304 Aiken Center , Burlington, VT 05405
AU: Parker, S M
AF: University of Alabama, Box 870344 , Tuscaloosa, AL 35487
AU: Huryn, A D
AF: University of Alabama, Box 870344 , Tuscaloosa, AL 35487
AU: Green, A C
AF: The Ecosytems Center Marine Biologiacl Laboratory, 7 MBL ST, Woods Hole, ma 02543
AB: We used a ¹⁵N tracer addition to quantify nitrogen dynamics and foodweb interactions in two contrasting tributaries of the Ivishak River in the Arctic National Wildlife Refuge, Alaska. We added ¹⁵NH₄Cl simultaneously to spring and mountain streams for 4 weeks in summer of 2002 and measured ¹⁵N: ¹⁴N ratios in inorganic and biomass compartments over distance and time. ¹⁵N labeling was rapid in both streams despite low temperatures and higher than expected discharge. Compartment-specific ammonium uptake lengths (Sw) in the flashy mountain stream were initially high (7 km) due to elevated discharge, but decreased significantly thereafter (200-400 m). Uptake lengths in the hydrologically stable spring stream were similar throughout the release, but varied slightly between compartments (80-150 m). Most of the added ¹⁵N-NH₄ in the spring stream was taken up by bryophytes, whereas active uptake of N in the mountain stream was by filamentous algae. Chironomids (Diamesinae and Orthocladiinae) appeared to be feeding primarily on epilithon and filamentous algae, whereas simuliids were feeding on seston in both streams. Our data show that nitrogen retention in the two streams differed and depended on turnover of organism biomass, which was controlled by physical conditions such as temperature and discharge variability.
DE: 1615 Biogeochemical processes (4805)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly