Absorption Spectra as Predictors of Algal Biomass and Pigment Content of the Cultured Microalgae Amphidinium carterae, Isochrysis galbana, Nephroselmis sp., and Anabaena sp.

Background: In the search of a rapid and representative method for the approximate calculation of culture density and cell content of useful pigments, the study of absorption spectra of cultures of the dinoflagellate Amphidinium carterae, the haptophyte Isochrysis galbana, the chlorophyte Nephroselmis sp., and the filamentous cyanobacterium Anabaena sp. were selected as representative species of different taxa. Methods: The experimental cultures were established in small volumes by the discontinuous method under 20–21 °C, salinity of 30 or 40 ppt, and 2000 or 8000 lux illumination, and the absorbance spectra, density of the culture and concentration of the extracted pigments chlorophyll, total carotenoids, and phycocyanin were recorded during cultivation. Results: Algal density can be predicted sufficiently correctly because the regression equation of the correlation of the OD value of 750 nm from each absorption spectrum and the measured algal biomass was very strong. The same is true for the corresponding correlations between OD 750 nm and the detected pigments. Conclusions: Absorption spectra of microalgal cultures can be a simple, inexpensive, and non-invasive method for the growers to obtain the necessary information for predicting the right time to collect an ideal combination of maximum biomass and useful pigments, provided that the interpretation of the spectra is performed according to the method described herein.