Variable Respiration in Aquatic Plant Communities

Test species for the study, which was run in continuous flow and batch type respirometers, included the aquatic macrophytes Potamogeton crispus and Elodea candensis. Consumption rates were found to be dependent on temperature, state of plant maturity, and the oxygen concentration of the test water. Uptake rates were best described by the linear relationship: R = β + αC. Values of β were observed to vary from 0.21 to 0.87 mg gm−1hr−1 with corresponding values of α ranging from 0.04 to 0.09 lgm−1hr−1. Consumption rates varied from 0.2 to 2.8 mg O2 gm dry weight per hr for dissolved oxygen concentrations of 0 to 18 mg per l. A methodology is presented to estimate primary productivity in aquatic ecosystems from observations of the diurnal variation of dissolved oxygen incorporating a variable community respiration rate.