Wednesday, June 6, 2007 - 8:00 AM
190

Linking nitrate uptake, metabolism, and calcium carbonate deposition in a travertine stream

Catherine A. Gibson1, Jane Marks2, and Bruce A. Hungate2. (1) Biology and Environmental Studies Program, Skidmore College, 815 N. Broadway, Saratoga Springs, NY 12866, (2) Biology, Northern Arizona University, PO Box 5640, Flagstaff, AZ 86011

Travertine streams offer a unique opportunity to examine the roles of biotic, chemical, and geological processes in nutrient dynamics.  We examined nitrate uptake along a discharge and calcium carbonate deposition continuum in a travertine stream, Fossil Creek, Arizona, on three dates in an 18 month period.  We hypothesized that areas of high travertine formation, as expressed by calcium carbonate deposition, would have greater nitrate uptake velocity and total ecosystem metabolism. We conducted short-term nutrient addition experiments at each of the four sites with bromide as a conservative tracer.  Discharge ranged from 1345 to 7 L s-1 at the four sites due to water withdrawl for hydropower generation.  Calcium carbonate deposition ranged from 0 to 3.76 x 10-5 g day-1.  Nitrate uptake velocity was highly variable, ranging from 59 mm min-1 to 0.4 mm min-1.  Area specific uptake rate varied considerably across the sites ranging from 233 to <1 mg m-2 hr-1.  These data include some of the highest rates of nitrate uptake velocity reported for stream ecosystems.  Uptake velocity was positively correlated with total ecosystem metabolism, but not with calcium carbonate deposition.