A REMOTE-SENSING REFLECTANCE MODEL OF A RED-TIDE DINOFLAGELLATE OFF WEST FLORIDA

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 7-77 mg m-3 found in the case 2 waters along the west Florida shelf [USA] in Oct. 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 (gelbstoff 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.