Comparison of 14 CO 2 and 12 CO 2 Uptake and Release Rates in Laboratory Cultures of Phytoplankton

The accuracy of the 14 C method of estimating photosynthetic rates was evaluated by comparing inorganic 14 C and 12 C uptake and release rates in three species of microalgae. Net photosynthesis was defined as the net decrease in inorganic 12 C concentration during a given light period. The axenic algae cultures were incubated in a continuous flow-chamber system and the experiments conducted as time-course studies in light and dark. All experiments were characterized by higher 14 C uptake rates than 12 C during the first part of the light period, but in many of the experiments the 14 C uptake approached the 12 C net photosynthesis by time (...)