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.