Backscattering properties of marine phytoplankton Prorocentrum micans

Backscattering coefficients of Prorocentrum micans were determined in the laboratory using the Hydroscat-6 instrument. Ancillary parameters measured included absorption and scattering coefficients, chlorophyll-a concentration, cell size, and cell concentration. Spectral variability was found in the case of the backscattering coefficients, and the maximum backscattering coefficient was obtained at 488 nm, which deviated from the theory because of pigment absorption. We were unable to detect the effect of chlorophyll fluorescence on the shape of the backscattering coefficient spectra at 700 nm. However, the particulate backscattering coefficient was found to be well correlated with chlorophyll-a concentration at the six chosen wavelengths. At the same time, the backscattering ratio was accurately arranged in the range 0.012 to 0.019 at 442 nm and 0.013 to 0.021 at 620 nm. A positive correlation between particle density and backscattering ratio was established with a nonlinear regression model and the correlation coefficient was as high as 0.96 at 442 nm, this providing a good foundation for improving the accuracy of identifying the red tide alga, P. micans, for water colour remote sensing.