This paper presents angular and spectral measurements of the functions that create a scattering matrix (Mtiller matrix). The investigations were carried out on monocultures of the unicellular phytoplankton ChZoreZEa vulgar-is, ChZoreZZu kesleri, and Chroococcus minor at scattering angles from 8" to 155" and at wavelengths of 488, 514, and 633 nm. Living cultures of phytoplankton as well as cultures treated chemically (boiled in 5% NaOH) and physically (ultrasound) were tested. These treatments alter the internal structures of the cells, and show that the altered structures modify the scattering matrix functional.