HR: 1330h
AN: B33E-19    [Abstracts]
TI: The Influence of Dam Discharge Regime and Canyon Orientation on Ecosystem Metabolism in the Colorado River
AU: * Kennedy, T A
EM: tkennedy@usgs.gov
AF: Grand Canyon Monitoring and Research Center, 2255 N. Gemini Dr., Flagstaff, AZ 86001 United States
AU: Tietjen, T
EM: ttietjen@CFR.MsState.Edu
AF: Department of Wildlife and Fisheries, Mississippi State, A203 Thompson Hall Mail Stop 9690, Mississippi State, MS 39762 United States
AU: Wright, S
EM: sawright@usgs.gov
AF: Grand Canyon Monitoring and Research Center, 2255 N. Gemini Dr., Flagstaff, AZ 86001 United States
AB: Since the closure of Glen Canyon Dam and the beginning of flow regulation of the Colorado River in Grand Canyon in 1963, considerable efforts have been directed toward understanding the aquatic ecology of this altered ecosystem. Understanding what controls resource availability has been a central focus of these efforts because the Colorado River supports populations of sport fish and endangered humpback chub, both of which appear to be strongly resource limited. There is evidence that dam discharge regime and canyon orientation influence algal standing crop due to their effects on water velocity (scour) and solar insolation, respectively. We explored whether these physical factors influenced rates of primary production and ecosystem respiration, two different metrics of resource availability, in the clear tailwater section of the Colorado River by conducting whole system metabolism measurements across a range of discharge regimes and in reaches with different orientation (i.e. N-S vs. E-W). We found that while both discharge regime and canyon orientation influence rates of primary production, seasonal changes in light availability appear to have a far stronger influence on rates of primary production in the Colorado River. Water temperature appeared to be the main driver of ecosystem respiration.
DE: 4239 Limnology
DE: 4805 Biogeochemical cycles (1615)
DE: 4853 Photosynthesis
SC: Biogeosciences [B]
MN: 2005 Joint Assembly