4.3. Calculations
Fort the calculation of biomass productivity, cultures were run until they increased 2.5 - 4 times the initial OD750, making sure there were no signs of culture approaching the stationary phase of growth. This took as short as two days for the Fortaleza simulated-weather or as long as 7 days for Comodoro Rivadavia winter simulated-conditions. Adjustments were made in the calculations to subtract the inoculated biomass, medium volume and biomass removed, and evaporation at each data point. For evaporation rate, the height of the culture’s surface was labeled in the ePBRs at each data point and the volumes were determined after removing the culture at the end of the run and adding known volumes of water to the vessels up to each label. The maximum evaporation rates (last sampling time points) across the study were 10-15%, 25-30%, or 30-33% for 20 cm-, 10-, or 5 cm-deep simulated ponds.
The biomass productivity was calculated as the dry-biomass produced during the elapsed time and the area exposed to light and expressed in g · m- 2 · d-1. The productivity of lipids and carbohydrates was calculated essentially following the same criterion as that for biomass.
For the general model of South American mean annual biomass productivity depicted in Figure 1 the heat map was generated with Q-GIS 3.12 and the semi-empirical biomass productivities obtained by cultivating S. obliquus under climate-simulated conditions in ePBRs.