ALGAL C-14 AND TOTAL CARBON METABOLISMS .2. EXPERIMENTAL-OBSERVATIONSWITH THE DIATOM SKELETONEMA-COSTATUM

Three sets of comparisons of net and gross inorganic carbon assimilati on and C-14 uptake were made with an axenic culture of Skeletonema cos tatum. The comparisons showed that in the physiological window studied (10-20% of the intrinsic generation time and gross photosynthesis/res piration ratios of 2-3), C-14 uptake into the particulate plus the dis solved fractions approximated to net photosynthesis. Rate constants de rived from the chemically determined changes were used to parameterize models that accounted for the respiration of photosynthetic products and for the recycling of respiratory CO2. The conclusion drawn was tha t over the time scale studied, the C-14 technique was measuring net ph otosynthesis, consistent with essentially 100% recycling of respirator y CO2. The study has shown that we now possess the basis to make a rig orous analysis of net, gross CO2 fixation and net C-14 uptake, and for ms the first step in the development of algorithms for the interpretat ion of C-14 field observations.