HR: 16:00h
AN: NB24F-03    [Abstracts]
TI: What controls nitrate removal in streams of varying land use?
AU: * Tank, J L
EM: tank.1@nd.edu
AF: University of Notre Dame, Dept. of Biological Sciences, Notre Dame, IN 46556 United States
AU: Bernot, M J
AF: University of Notre Dame, Dept. of Biological Sciences, Notre Dame, IN 46556 United States
AU: Hamilton, S K
AF: Michigan State University, Kellogg Biological Station, Hickory Corners, MI 49060 United States
AU: Hall, R O
AF: University of Wyoming, Dept. of Zoology and Physiology, Laramie, WY 82071 United States
AB: In the 2nd year of a 3 year, multi-biome project, we quantified 15N-nitrate removal in streams of varying land use (native vegetation, agriculture, and urban) in southwestern Michigan and Jackson, Wyoming and we found distinct patterns in nitrate removal compared to the first year of the study. Water-column nitrate concentrations ranged from 1-165 ugN/L in Wyoming and 80-648 ugN/L in Michigan. Atypically, agricultural streams had the lowest nitrate concentrations in both biomes at the time of tracer additions. Whole-stream nitrate uptake was highest in the urban stream in Michigan (3.4 ugN/m2/s) and lowest in the stream draining pasture in Wyoming (0.15 ugN/m2/s) but was not simply related to areal denitrification rate or whole-stream metabolism (e.g. primary production or community respiration). However, relative nitrate demand (as uptake velocity) and whole-stream metabolism were related to stream width and discharge. Denitrification was highest in the native vegetation stream in Wyoming (0.66-1.1 ugN/m2/s), and lowest in the agricultural stream in Michigan (0.03-0.06 ugN/m2/s), but denitrification was not related to nitrate concentration. In Wyoming, denitrification represented a larger proportion of nitrate uptake than in Michigan streams. Understanding the relative importance of mechanisms controlling water-column nitrate removal will be critical in managing watershed nitrogen export.
DE: 1806 Chemistry of fresh water
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly