Description

Abstract: Planktonic community respiration rates were assessed every 30 min through two 48-h periods in near-surface water taken automatically from a fertilized earthen pond and incubated in a plastic chamber for 21 min of each sampling cycle. Parallel records of water temperature, air temperature, windspeed, and solar irradiance permitted calculation of gross and net primary production and photosynthesis-irradiance relationships. Nighttime respiration rates Generally matched oxygen depletion rates in pond water, indicating that incubation-based rates were representative of a quickly darkened pond community throughout the day. Daytime rates averaged nearly 2 times the mean night rate and 58% higher than the mean day rate determined by a typical interpolation used in free-water production calculations. Daily gross production ranged from 0.7 to 1.2 mmol O2 liter-1 d-1; respiration constituted 65-75% of gross rates. Gross oxygen production per unit Chl a during sampling intervals was light saturated at irradiance values > 600