Laser induced fluorescence imaging: application to groups of macroalgae identification

Up to now, no technique was available to perform inventories and surveys of immersed macroalgae. This article presents a method making it possible to discriminate between macroalgae and seafloor and to identify the various ma croalgae. groups (green, brown or red). To our knowledge, this is the first excitation-emission matrix (EEM) of macroalgae ever carried out allowing t he identification of the spectral characteristics of each macroalgae group. Fluorescence imaging provides the spatial dimension besides spectral prope rties. An optical parametric oscillator (OPO) laser excites a test scene of macroalgae in a seawater aquarium. Laser-induced fluorescence images from 400 to 640 nm displayed by steps of 10 nm are filtered at 680 nm. Their ana lysis, combined with the water depth parameter, leads to an identification method for macroalgae. groups in a false-colour image: each of the three ma croalgae. groups is enhanced by one defined threshold on this false-colour image.