Harmful Algal Blooms (HABs) are recurring events in the coastal ocean, and local economies that depend on beach an dcoastal use are often adversely affected by these events. Inherent optical properties (absorption and backscattering) of the HAB dinoflagellate Lingulodinium polyedrum were measured in order to develop specific index that would enable easier detection of this HAB organism in the field. It has been noticed that red to blue and red to green ratio of absorption in this species is much lower then other measured species. A red tide ratio was tested in the field during a red tide episode in the San Pedro Channel, using a Wetlabs acS flow-through system. The red tide index gave a distinguishable signal in areas where L.polyedrum was present. Remote sensing reflectance was calculated from field and laboratory IOP measurements, using reverse Quasi-Analythical Alghoritm and Hydrolight to evaluate if the red tide index can be detected in the remote sensing ocean color measurements.Cetinic, I., L. Karp-Boss, E. Boss, M.A. Ragan, and B.H. Jones, 2007. Red tide optical index: in situ optics and remote sensing models. Eos Trans. AGU, 88(23), Jt. Assem. Suppl., Abstract OS23E-12.