Laser fluorescence diagnostics of phytoplankton under saturation conditions

A theory of nonlinear fluorescence of phytoplankton is developed on the basis of a model of the structure of its photosynthetic unit. It is shown that the main role in fluorescence saturation is played by singlet–singlet annihilation. An analysis of the expressions obtained can be used to identify the parameters proportional to the concentration of chlorophyll a. Theoretical predictions (nature of the saturation curve, proportionality of the identified parameters to the concentration of chlorophyll a found by conventional extract method) are supported by experiments carried out on three pure seawater algae cultures.