Optical Properties of Dense Algal Cultures Outdoors and Their Application to Remote Estimation of Biomass and Pigment Concentration in Spirulina Platensis (Cyanobacteria)1

Reflectance and vertical attenuation coefficient spectra from 400 to 1100 nm were investigated in detail on dense algal cultures of Spirulina in order to create algorithms for remote estimation of pigment and biomass concentration. Reflectance and the vertical attenuation coefficients were compared with biomass and pigment concentration in outdoor algal cultures. For assessing biomass concentration, the sum of reflectance above the base line from 670 to 950 nm was used. This allows the estimation of biomass with an error of less than 0.06 g·L−1 For chlorophyll a and phycocyanin estimation, vertical attenuation coefficients at the wavelengths 440 nm (or 676 nm) and 624 nm, respectively, were employed. The developed algorithms were tested by using independent data sets in the range of chlorophyll a from 0.2 to 20mg·L−1 and biomass from 0.15 to 1.1 g·L−1. An error of pigment estimation of less than 0.80 mg·L−1 was achieved. The potential use of the algorithms in algal biotechnology is further discussed.