Modeling Nitrate Uptake Via A Tracer Injected Into A Bacteria-Dominated, Polar Desert Stream
Koch, Joshua C 1 ; McKnight, Diane M 2 ; Cozzetto, Karen D 3
1 Institute for Arctic and Alpine Research, University of Colorado
2 Institute for Arctic and Alpine Research, University of Colorado
3 Institute for Arctic and Alpine Research, University of Colorado
A 33 hour tracer injection was conducted in Huey Creek, a glacial meltwater stream in the McMurdo Dry Valleys of Antarctica. This stream contains minor amounts of algae and no higher organisms. Nutrient cycling can thus be attributed mainly to processing by bacteria. Streamflow in the Dry Valleys correlates to sun angle (Conovitz 1998) and varied between 2 and 5 cfs during the experiment. Such variation has implications for hyporheic exchange and bacterial activity. Rates of nutrient exchange between the hyporheic zone and the stream will be determined using OTIS, a transport model that accounts for water storage and exchange. While previous Huey Creek models included temporally-constant values for hyporheic zone storage and exchange rates, the large variability in streamflow suggests the need to vary these model inputs. Stream, below-stream, and lateral well samples were collected and will be used in conjunction with observations of wetted areas and channel braids to determine storage zone areas. Once physical variability in hyporheic storage and exchange are constrained it will become possible to quantify bacterial rates and processes responsible for nitrate depletion in the stream and subsurface of Huey Creek.
Conovitz, P. A., McKnight, D. M., MacDonald, L. H., Fountain, A. G., and H. R. House, 1998, Hydrologic processes influencing streamflow variation in Fryxell Basin, Antarctica. Ecosystem dynamics in a polar desert: The McMurdo Dry Valleys, Washington, DC, American Geophysical Union, p. 93-108.