Variability of the backscattering characteristics of the alga amphidinium carterae hulburt and its interpretation were examined using the measured data performed during July 2012 in the laboratory. The results indicated that the backscattering coefficient has the characteristic of spectral variability, and was highly power correlated with the chlorophyll concentration, the minimum of the correlation coefficient reached up to 0.96; otherwise, the shape of the particulate backscattering coefficient spectra was also changed from the low chlorophyll concentration to the higher concentration because of the influence of chlorophyll absorption. At the same time, the authors got another value of the particulate backscattering ratio ranging between 0.006 4 and 0.011 6 at 620 nm, although a global increase in particulate backscattering ratio with growing chlorophyll concentration was also visible, but the regularity is not obviously especially at the higher chlorophyll concentration and unlike backscattering coefficient, the spectral shapes of the backscattering ratio remained constant. The authors also found that particle density was one of the main factors controlling the variability of particles backscattering ratio for the pure algal water, and the authors fit a power law function to them and the correlation coefficient at 620 nm was as high as 0.98.