_Applied_  
_sciences_  
_Article_  
**Cultivating Microalgae in Desert Conditions: Evaluation of the Effect of Light-Temperature Summer Conditions on the Growth and Metabolism of _Nannochloropsis_ QU130**  
**[PERSON] 1,2, [PERSON] 1, [PERSON] 1, [PERSON] 2, [PERSON] 3 and [PERSON] 1,**  
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1 & CNRS, GEFEA, UMR 6144, Universite de Nantes, Oniris, F-44600 Saint-Nazaire, France; \\  & [EMAIL_ADDRESS] (H.A.J.); [EMAIL_ADDRESS] (A.T.); [EMAIL_ADDRESS] (R.T.) \\
2 & Algal Technologies Program, Centre for Sustainable Development, College of Arts and Sciences, \\  & Qatar University, Doha 2713, Qatar; [EMAIL_ADDRESS] \\
3 & PROMBS-CNRS, UPR 8521, Tecnosud, Rambla de la Thermodynamique, 66100 Perpignan, France; \\  & [EMAIL_ADDRESS] \\
* & Correspondence: [EMAIL_ADDRESS]; Tel.: +33-02-4017-2669; Facc +33-0-2401-7268 \\ \end{tabular}  
**Abstract: Temperature and light are two of the most crucial factors for microalgae production. Variations in these factors alter their growth kinetics, macromolecular composition and physiological properties, including cell membrane permeability and fluidity. The variations define the adaptation mechanisms adopted by the microalgae to withstand changes in these environmental factors. In the Qatar desert the temperature varies widely, typically between 10\({}^{\circ}\) and 45 \({}^{\circ}\)C There are also wide variations in light intensity, with values of over 1500 \(\upmu\)mol\({}_{\rm{hy}}\cdot\)m\({}^{-2}\)s\({}^{-1}\) in summer. A study of the effects of these thermal and light fluctuations is therefore essential for large-scale outdoor production systems, especially during the summer when temperature and light fluctuations are at their highest. The aim of this work is to study the impact of temperature and light intensity variations as encountered in summer period on the _Nannochloropsis_ QU130 strain, which was selected for its suitability for outdoor cultivation in the harsh conditions of the Qatar desert. It was carried out using lab-scale photobioreactors enabling simulation of both constant and dynamic temperature and light regimes. Biomass productivity, cell morphology and biochemical compositions were examined first in constant conditions, then in typical outdoor cultivation conditions to elucidate the adjustments in cell function in respect of fluctuations. The dynamic light and temperature were shown to have interactive effects. The application of temperature cycles under constant light led to a 13.6% increase in biomass productivity, while a 45% decrease was observed under light and temperature regimes due to the combined stress. In all cases, the results proved that \(N\). sp. QU130 has a high level of adaptation to the wide fluctuations in light and temperature stress. This was shown through its ability to easily change its physiology (cell size) and metabolic process in response to different cultivation conditions.  
**Keywords:** microalgae; culture; desert; temperature; light; _Nannochloropsis_  
**Highlights:**  
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1 & Nannochloropsis QU130 showed a high level of acclimation to high light and temperature \\  & Light and temperature effects on growth and metabolism were found to be related \\  & Biomass productivity improved under temperature cycles with constant light \\  & Light and temperature regimes induced a combined stress with 45% productivity loss \\  & Nannochloropsis QU130 demonstrated benefits for outdoor culture in harsh desert conditions \\ \end{tabular}