Microalgae processes exhibit a remarkable complexity due to the interaction of multiple phenomena that span multiple time scales, ranging from milliseconds to days, and from nanometres to hundreds of meters in industrial plants, involving quantum phenomena, cell metabolism, turbulence and fluid flow behaviour, light diffusion, mass and energy transport phenomena, interactions with the equipment design, and environmental phenomena.

Just to focus on the photosynthetic mechanism:

• photoproduction, i.e. the collection of all processes from photons utilisation to CO2 fixation, occurs in a fraction of a second;
• photoinhibition, i.e. the loss of photosynthetic production due to excess of light, acts on time scales of minutes to hours;
• photoregulation, i.e. the set of mechanisms by which microalgae protect photosynthetically active components via the dissipation of excess energy as heat, also occurs within minutes;
• photoacclimation, i.e. the ability of microalgae to adjust their pigment content and composition under varying light and nutrient conditions, acts on time scales of hours to days;
• mechanisms for nutrient internalisation by interacting with photosynthetic processes, occur within hours to days.