A remote‐sensing reflectance model of a red‐tide dinoflagellate off west Florida1

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Abstract
A mathematical model that simulates the spectral curves of remote‐sensing reflectance of blooms of the red‐tide dinoflagellate Ptychodiscus brevis is developed. The model is compared to measurements obtained from a low‐flying helicopter for P. brevis populations with chlorophyll‐like pigment concentrations from 7 to 77 mg m−3 found in the case 2 waters along the west Florida shelf in October 1983.The model simulates the effects of backscattering from water, phytoplankton, and detritus, and the effects of absorption due to water, phytoplankton, detritus, and yellow dissolved matter (“Gelb‐stoff”) for case 1 and case 2 waters. It can be easily modified to simulate the spectral reflectance of phytoplankton from other pigment color groups. Matching the model spectral curves to measured remote‐sensing reflectance curves provides accurate estimates of chlorophyll a plus pheophytin a and also estimates of Gelbstoff and detritus concentrations. Comparison of remote‐sensing reflectance data to model reflectance data allows calculation of the quantum efficiency of fluorescence for a given phytoplankton population, which provides a remote measurement of a factor that has been found to increase with the nutrient stress of the population.