LIGHT INDEPENDENT CARBON FIXATION BY MARINE MACROALGAE1

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Abstract
Several marine macroalgae representative of the Chlorophyceae, Rhodophyceae and Phaeophyceae were investigated for their potentials of photosynthesis and light independent (dark) carbon fixation. In addition, the activities of ribulose‐1,5‐bisphosphate carboxylase (RubP‐C; EC 4.1.1.39) and of phosphoenolpyruvate carboxykinase (PEP‐CK; EC 4.1.1.32) were studied. In contrast to the green and red algae investigated, all brown algae exhibited comparably high rates of dark fixation accounting for up to 20% of photosynthetic carbon uptake. These observations are confirmed by the activities of RubP‐C and PEP‐CK measured after extraction from different species and thallus regions. Dark fixed 14C was mainly recovered from aspartate, citrate, malate, glutamate, and alanine. Appreciable amounts of 14C were incorporated into insoluble (polymeric) constituents even after relatively short periods of dark fixation.