CHEMICAL CHANGES IN THE GROWTH MEDIUM OF MICROCYSTIS, BATCH CULTURES GROWN AT STRESS AND NON-STRESS LIGHT INTENSITIES

Abstract

The modified BG 11 growth medium used in this study has a poor buffer ability and large pH changes occurred during growth of Microcystis. Inhibition of growth in cultures grown at stress light intensity (26 μEinst m⁻² sec⁻¹) could be ascribed to depletion of the total inorganic carbon content of the medium rather than to light intensity per se, pH or high O² concentration. In cell suspensions grown under stress light intensity an unfavourably low CO₂: O₂ concentration ratio developed due to rapid photosynthesis and insufficient replenishment of CO₂ by diffusion from air which may have induced oxygenation instead of carboxylation by ribulose diphosphate carboxylase.