Performance of pCO2 parameters over the course of the experiment was consistent, with the exception of the high CO2/low light/high temperature treatment applied in the final week of the experiment. In this treatment, pCO2 increased from the target level of 820ppm to a higher level of 1176 ppm. This was probably due to the increased temperature, which caused an increase in respiration rate (and biological CO2 production), but not a concomitant increase in photosynthesis rate due to the light limitation of that treatment. We could not intervene to compensate for this anomaly by decreasing the level of the CO2 treatment, as the treatment was supplied to the header tanks, each of which supplied both high temperature and low temperature tanks.