Effects of the Diurnal Light and Temperature Fluctuations on the Growth, Photosynthesis and Biochemical Composition of Terrestrial Oleaginous Microalga Vischeria sp. WL1 (Eustigmatophyceae)

Dynamic changes in diurnal light and temperature are a natural phenomenon, particularly pronounced in arid environments. However, it remains unclear whether the coupling of diurnal light and temperature fluctuations contributes to the capability and evolution of lipid accumulation in arid terrestrial microalgae. Here, we characterized the effects of diurnal light and temperature fluctuations on the growth, photosynthesis, lipids, carbohydrates, proteins and fatty acids in Vischeria sp. WL1, an oil-producing Eustigmatophyceae microalga sourced from an arid steppe. The photosynthetic activity parameters (Fv/Fm, PIabs, ψ0 and φE0) were the highest, while parameters of damage and energy dissipation (Wk and DIO/RC) were the lowest, under the diurnal light cycle (DLC) among all conditions and then followed by the diurnal light–temperature cycle (DLTC). DLTC led to reduced growth and biomass but enhanced lipid accumulation, with lipid content reaching a maximum of 54.7% on day 4. This observation may suggest a carbon reallocation from carbohydrates toward lipid synthesis. DLTC resulted in an increase in the saturated fatty acids (SFA) content on day 12 and only in C18:2 among polyunsaturated fatty acids (PUFA) on day 4 while lowering eicosapentaenoic acid (EPA) concentration and content on day 12. Together, our findings will contribute to the understanding of the adaptive strategies of terrestrial microalgae to the arid environment, as well as the beneficial clues for exploring terrestrial microalgae for oil production.