The estimation of the yearly cycle of submarine irradiance for ecological purposes. A methodological example based on data from Banyuls-sur-Mer (France)

The yearly cycle of surface solar irradiance at Banyuls-sur-Mer is derived from meteorological data. Monthly irradiance attenuation coefficients of the seawater were obtained from Secchi disc readings, which enabled the authors to classify the monthly optical water types according to Jerlov's classification. The average daily values of submarine irradiance are calculated for each month, and for different depths. Calculations have been carried out for the visible spectrum (350-710 nm) subdivided into 20 nm bands. Submarine irradiance is given in energetic (cal cm-² day-¹) as well as quantum (µE m-² ѕ-¹) units. Some considerations are given for underwater stations with different degrees of exposition to available light.