The Influence of Elevated CO(2) Concentrations on the Growth of Various Microalgae Strains

The influence of elevated CO(2) concentrations on the growth and viability of various microalgae strains was studied. Arthrospira platensis, Chlorella ellipsoidea, Chlorella vulgaris, Gloeotila pulchra, and Elliptochloris subsphaerica were tested. The cultivation of microalgae was carried out at constant CO(2) concentrations (0.04, 3, 6, or 9%—sequentially from lower to higher concentrations), under constant (24 h·day(−1)) illumination with an intensity of 74.3 µmol quanta·m(−2)·s(−1), and a constant temperature of 23.5 ± 0.5 °C. The optical density of the microalgae biomass, pH, and the chemical composition of the culture medium were measured. Microscopy (including the cytochemical microscopic method) was conducted to monitor the state of the microalgae. The highest biomass growth rate (0.37 g·L(−1)·day(−1)), among all experiments, was achieved for Chlorella vulgaris at CO(2) = 3% and for Chlorella ellipsoidea at CO(2) = 6 and 9%. The lowest growth rate (0.12 g·L(−1)·day(−1)) was achieved for Arthrospira platensis at CO(2) = 3 and 9%. The microscopy results showed the absence or a minimum number of dead cells of the strains under selected conditions. The ability to maintain the viability of cultures up to significant concentrations of CO(2) = 9% was due to adaptation (gradual increase in CO(2) concentrations in the experiments).