Abstract: An inverse hydrologic optics problem is solved using a proposed curve concavity criterion in order to reconstruct the vertical Chlorophyll concentration profile from synthetic water-leaving radiance experimental measurements in the ocean water for 10 wavelengths (multi-spectral approach) and 10 upward polar directions. The inverse problem is formulated as an optimization problem and iteratively solved by the Ant Colony Optimization (ACO) metaheuristics, using as direct model the radiative transfer equation, that is solved by the Laplace transform discrete ordinate (LTSN) method. An objective function is given by the square difference between computed and experimental radiances at every iteration. The reconstructed profile show a good agreement with the reference gaussian profile ofChlorophyll concentration.