Ecological Systems and Devices Annotation << Back Changes in the Toxicity of K2 Cr2 O7 and SDS for the Green Algae Chlorella vulgaris Beijer Depending on the Lighting Mode Lazareva А.М., Filippenko I.А., Kanygin I.V., Georgievskaya K.A., Valitova D.I. The study examined the effects of different lighting regimes on the toxicity of potassium dichromate and sodium dodecyl sulfate (SDS) on the green alga Chlorella vulgaris Beijer. The study was conducted for three lighting regimes: 12N/12D, 6N/6D/6N/6D, and 24N/0D, where N is the number of hours of algae cultivation without light and D is with light. The test culture condition was assessed by changes in optical density, pH, photosynthetic efficiency, and maximum and minimum fluorescence. The 6N/6D/6N/6D illumination regime stimulated cell growth in the test culture and enabled the highest maximum and minimum fluorescence values for the C. vulgaris culture. The lighting regime influenced the toxicity of both K2 Cr2 O7 and SDS. Potassium dichromate stimulated C. vulgaris growth under 12N/12D illumination, while under 6N/6D/6N/6D illumination, it significantly reduced culture abundance. SDS additions under 12N/12D and 6N/6D/6N/6D significantly reduced maximum and minimum fluorescence levels, as well as photosynthetic efficiency values, of the test culture relative to the control. In experiments with both K2 Cr2 O7 and SDS, under 24N/0D illumination, toxicant additions had little effect on C. vulgaris photosynthetic efficiency, causing significant suppression of maximum and minimum fluorescence values. Keywords: Potassium dichromate, sodium dodecyl sulfate, Chlorella vulgaris, toxicity, lighting mode, circadian rhythms. DOI: 10.25791/esip.5.2026.1595 Pp. 44-53.