Photosynthetic and Respiratory Processes: An Open Stream Approach

This investigation examined open-stream methods for detection of photosynthetically driven (light dependent) chemical change, and subsequently provided an estimate of flood effects on the photosynthetic community in the 25-km reach of the Colorado River below Glen Canyon Dam. Observations reported here confirm that the dynamics of oxygen concentration and pH are correlated because photosynthesis and respiration in the benthic community cause the diel patterns. Observations at the constant low flows immediately before and after the controlled flood permitted measurement of changes in stream chemistry caused by biological activity and provided a test of the hypothesis that plants were scoured from the channel by the flood. The diel amplitudes of oxygen concentration and pH change were decreased after the flood as the biomass was scoured. Patterns of oxygen production and carbon dioxide removal varied along the 25-km reach.