Chlorophyll fluorescence effects in the red part of reflectance spectra of natural waters

Abstract

Solar-induced fluorescence of algal pigments can be (remotely) measured in productive water masses. Detection of the peak related to this fluorescence in the red part of the reflectance spectra can then be used for the (remote) assessment of the biomass, particularly in the waters where other optical determination methods fail. To study the chlorophyll fluorescence effects in natural waters a two-flow radiative transfer model was developed and measurements were performed in turbid coastal waters. Several phenomena, including the influence of the suspended and dissolved materials on the height and the position (shift) of the peak, and the effects of the vertical stratification of the water column, are described. The observed shift of the reflectance maximum to the longer wavelength appears to be inherent to the presence of the particular material in the water. Reflectance values near the sea surface in the red part of the spectrum are only little influenced by the stratification.