A form of scattering in which a photon is very briefly absorbed by a molecule, then immediately re-emitted at a longer (less energetic) wavelength. Because some energy is retained by the molecule, this is referred to as inelastic scattering.
Fluorescence is of interest to oceanographers primarily as a means of detecting chlorophyll, and secondarily for detecting colored dissolved organic material, artificial dyes, and other fluorescent compounds. Each compound has characteristic excitation and emmision spectra, and fluorometers discriminate between compounds by generating and detecting light within corresponding specific wavelength ranges.