Algal cell size and the maximum density and biomass of phytoplankton1

The maximum density that algal cells can reach in culture varies as the −1.27 power of the cell volume. This size‐dependent density boundary results in a size‐dependent biomass boundary, with the maximum biomass changing as the −0.32 power of cell volume. The existence of size‐dependent maximum biomass and density appears to be the consequence of algal self‐shading, the efficiency of light absorption by algae, and their effect on light absorption being dependent on cell size. The size‐dependent density and biomass boundaries are comparable to the qualitatively similar boundary described by the −3/2 power rule for higher plants.