Fellows, C. S. University of New Mexico, cfellows@sevilleta.unm.edu
Dahm, C. S. University of New Mexico, cdahm@sevilleta.unm.edu
Valett, H. M. Virginia Polytechnic Institute and University, mvalett@vt.edu

 
CONTRIBUTION OF THE HYPORHEIC ZONE TO ECOSYSTEM METABOLISM IN TWO MONTANE STREAMS, NEW MEXICO, USA
 
Hyporheic zone respiration is often an important component of stream ecosystem metabolism and may be influenced by the magnitude of exchange between subsurface and surface water. Using benthic chambers, hyporheic sediment chambers, and whole-stream oxygen mass balance techniques, we measured metabolism in two low order montane streams, Rio Calaveras and Gallina Creek, in 1996 and 1997. Solute injections were used to determine discharge and transient storage (As/A), a measure of subsurface/surface water exchange. In 1996, whole-stream respiration (R) at Gallina Creek was more than 4x greater than at Rio Calaveras (-14.7 vs. -2.9 gO2/m2/day) and As/A at Gallina Creek was 10x greater (1.5 vs. 0.1). However, even when As/A values for the two sites were nearly equal in 1997 (0.07), R at Gallina Creek still exceeded that at Rio Calaveras by almost 2x (-4.4 vs. -2.3 gO2/m2/day). When the hyporheic zone respiration rate was calculated as the difference between whole-stream and benthic chamber R values, the hyporheic contribution to whole-stream R was consistently much greater at Gallina Creek than at Rio Calaveras. Calculations using these estimated rates and measured hyporheic sediment rates indicated that the ratio of hyporheic volume to stream channel volume was also much greater at Gallina Creek.
 
Day: Wednesday, Feb. 3
Time: 02:45 - 03:00pm
Location: Eldorado Hotel
 
Code: CS64WE0245E