Quantized nature of light and large-scale biomass production in unicellular algae

Usually, the analysis of the biomass production rate of unicellular algae in large-scale systems treats light intensity as a continuous variable. This is tantamount to accounting only for the average time gaps between consecutive photons in a light beam. However, total production is the cumulative effect of the operation of many photosystems in a cell and many cells in a culture. The performance of an individual photosystem depends crucially on the quantized nature of light: That time gaps between consecutive photons vary randomly and that the photosystem can process photons at a rate of, at most, one photon every (about) 10 ms. The question that arises is: Can one understand experimental observations in terms of constant parameters, namely, the average values of the statistically distributed entities, or does one have to take into account their statistical distributions? Studying several model scenarios, in which constant average values and/or the statistical distributions of photon time gaps and antenna cross section areas are considered. It is shown that the most significant effect on large-scale biomass production is that of the statistical distribution of photon time gaps in a beam, combined with the 10 ms rate-limiting time scale of photosystem performance.