Microalgae efficiently convert sunlight into lipids and carbohydrates, offering bio-based alternatives for energy and chemical production. Improving algal productivity and robustness against abiotic stress requires a systems level characterization enabled by functional genomics. Here, we characterize a halotolerant microalga Scenedesmus sp. NREL 46B-D3 demonstrating peak growth near 25 degrees C that reaches 30g/m(2)/day and the highest biomass accumulation capacity post cell division reported to date for a halotolerant strain. Functional genomics analysis revealed that genes involved in lipid production, ion channels and antiporters are expanded and expressed. Exposure to temperature stress shifts fatty acid metabolism and increases amino acids synthesis. Co-expression analysis shows that many fatty acid biosynthesis genes are overexpressed with specific transcription factors under cold stress. These and other genes involved in the metabolic and regulatory response to temperature stress can be further explored for strain improvement. Sara Calhoun, Tisza Ann Szeremy Bell, Lukas Dahlin and colleagues characterize the growth and biomass accumulation of a halotolerant microalga Scenedesmus sp. NREL 46B-D3. They sequenced the genome and profiled the transcriptomic and metabolomic response of this strain under high and low-temperature stress, and shed light on the genes involved in the metabolic and regulatory response to temperature stress.