What this work is about, in plain words
What happens to spirulina when it lacks phosphorus? The authors showed that in light the cells lose all their pigments but remain alive and recover after feeding.
The color of water and cultures is often used to judge the amount of algae: optical methods measure pigments rather than the biomass itself. However, the share of pigments in cells changes greatly depending on conditions. The authors studied what happens to the pigments and biomass of the cyanobacterium Spirulina platensis under deep phosphorus starvation.
The culture was deprived of phosphorus and kept at different light intensities or in darkness; then a portion of phosphates was added and recovery was monitored.
According to the authors, in light under phosphorus deficiency all pigments break down, and the biomass decreases with them. The brighter the light, the stronger the breakdown. The pigments break down faster than under nitrogen deficiency. Nevertheless, the cells remain viable: after phosphates are added, the pigment system fully recovers, and the rate of recovery depends on what the culture went through before. In darkness, pigments and biomass did not change for 8 days and then began to decline.
The work shows that the color of a culture does not unambiguously indicate its biomass. In addition, a lack of phosphorus quickly affects the pigments — important for anyone who needs the blue pigment of spirulina.
Limitations. These are laboratory experiments on one culture. The text of the article is available only as a scan; the explanation was written from the recognized text.