A new method for calculating subsurface currents of photosynthetically active radiation and consequences for calculating the production of phytoplankton in natural bodies of water

The described method is based on a) an empirical formula which links the measured subsurface currents of photosynthetically active solar radiation (PSASR) (at 350-700 nm) with the appropriate measured positions of the Sun and b) astronomical formulas for the position of the Sun relative to the time of the day, the day of the year, and the geographic latitude. In accordance with this, precise daily and annual integrals of the currents of PSASR and the form factors of the daily change in the PSASR current are given. Certain consequences for calculating the production of phytoplankton are discussed, in particular, the effect of the form factors of the daily changes in the PSASR current.