Physiological response to high-light intensities in two Chlamydomonas microalgae, one polar and one tropical

This study investigated the effect of different light intensities (120, 650, 725, 850, 1200, 2100, and 3250 µmol photons m⁻² s⁻¹) on the growth, biomass productivity, photopigment, and macromolecular composition in two Chlamydomonas microalgae: the polar Chlamydomonas sp. RCC2488 (malina) and the model C. reinhardtii . Intermediate light intensities (725 and 850 µmol photons m⁻² s⁻¹) significantly favored growth rate and biomass production in C. malina , whereas C. reinhardtti arrested growth at 850 µmol photons m⁻² s⁻¹ and halted growth at 1200 µmol photons m⁻² s⁻¹. Total chlorophyll content decreased from 1200 and 120 µmol photons m⁻² s⁻¹ in C. malina and C. reinhardtii , respectively. No changes in carotenoid content were observed in C. reinhardtii , while the content of this photopigment increased in C. malina from 1200 µmol photons m⁻² s⁻¹, suggesting higher photoprotection levels. Energy reserve metabolite accumulation was observed in C. reinhardtii from 725 µmol photons m⁻² s⁻¹, above 33% of the DCW. In C. malina , lipid accumulation (up to 31% of the DCW), mainly TAG, was promoted from 2100 µmol photons m⁻² s⁻¹. These results highlight the adaptability to different light intensities of the polar microalga and its potential for biotechnological applications under high light intensities focused on targeted production of biomass, lipids and photopigments.