Monitoring the chlorophyll content in microalgae biomass during cultivation can provide information about running the assimilation processes in the cell. Carotene is a secondary photosynthetic pigment with protective functions (especially photoprotection) in cells, which by virtue of its functional peculiarities, is dependent on light intensity. Different genetic programs are successively included during the life cycle, that ensure the survival of microalgae culture, which are inevitably expressed as changes in biosynthetic activity. All biosynthetic changes in Dunaliella salina biomass, which is a photoautotrophic organism, are determined by light intensity. The photosynthesis intensity depends on the biosynthesis of the pigments involved in light energy capture. The ratio of these two pigments values may be an evidence of the intensity of the metabolic or protection processes, and thus the state of Dunaliella salina culture. The results of biomass quantitative monitoring confirm different stages in the life cycle of Dunaliella salina under standard conditions. Thus, the Chlorophyll/Carotene amount ratio in Dunaliella salina biomass decreased during the first 48 hours, which testifies to the predominance of protection processes over assimilation ones. The next 48 hours this parameter is increasing, which talks about intensifying photosynthesis vis-à-vis the phenomena of cell protection. The maximum is achieved on day 4 of cultivation, as well as in amount of biomass, and the absolute content of chlorophyll and carotene monitored separately. We note that only the variations observed at the end of the second day of cultivation represent statistically reliable differences. In all other cases, quantitative differences from day to day occur only as trends of change, and have to be checked on bigger experimental lot.