INFLUENCE OF ENHANCED CO2 ON GROWTH AND PHOTOSYNTHESIS OF THE RED ALGAE GRACILARIA SP AND G-CHILENSIS

The influence of elevated CO2 concentrations on growth and photosynthesis of Gracilaria sp. and G. chilensis was investigated in order to procure information on the effective utilization of CO2. Growth of both was enhanced by CO2 enrichment (air + 650 ppm CO2, air + 1250 ppm CO2), the enhancement being greater in Gracilaria sp. Both species increased uptake of NO, with CO, enrichment. Photosynthetic inorganic carbon uptake was depressed in G. chilensis by pre-culture (15 days) with CO2 enrichment, but little affected in Gracilaria sp. Mass spectrometric analysis showed that O-2 uptake was higher in the light than in the dark for both species and in both cases was higher in Gracilaria sp. The higher growth enhancement in Gracilaria sp. was attributed to greater depression of photorespiration by the enrichment of CO2 in culture.