XVI International Botanical Congess
It is of general interest to know if the CO2 increase in the atmosphere could affect the photosynthesis of macroalgae in air during emersion. The photosynthesis of Enteromorpha linza (a green alga), Ishige okamurae (a brown alga) and Gloiopeltis furcata (a red alga), while exposed, was investigated as a function of CO2 concentrations and water loss. Their photosynthesis was not saturated at the present atmospheric CO2 level (350 ppm ), CO2 compensation point and Km[co2] increased with increasing desiccation, showing that desiccation lowers the algal CO2 affinity. E. linza, I. okamurae and G. furcata usually tolerates 3 to 5 h desiccation while the tide is low, and may benefit from increased atmospheric CO2 while exposed to air during such a period, especially when the algae have lost some water.