It is imperative that the intensity of incident light provided to the culture must be such that it maximizes astaxanthin production while minimizing its ill-effect on cell mortality.We hypothesized that an optimal incident light intensity for
maximum astaxanthin productivity can be created by starting the red stage culture with a proper initial biomass density (IBD).Here, we provide a detailed study of the effects of IBD ongrowth and astaxanthin accumulation of H. pluvialis at the red stage in an outdoor glass column photobioreactor. The photochemical efficiency of photosynthesis, specific growth rate,
pigment content, and biomass concentration were monitored as a function of IBD ranging from 0.1 to 5.0 g L−1 of cell dry
weight during different seasons, i.e., summer, fall, and winter