A three-layered sphere model of the optical properties of phytoplankton

Theoretical scattering computations are performed on a phytoplankton model consisting of three\ud concentric spheres. The outer sphere represents the wall, membrane, or frustule and is assigned a\ud relatively high index of refraction with no absorption. The middle layer represents the chloroplasts\ud and is assigned a relatively low index of refraction with absorption. The core represents the balance\ud of the cytoplasm and is given a low index of refraction with no absorption. The model is applied\ud to an observed size distribution from the Pacific central gyre. This model produced significantly\ud more backscattering and attenuation than a low-index, homogeneous-sphere model. Changing the\ud distribution of cell-wall thickness as a function of particle size produces much variation in the\ud shape of the volume scattering function