Reconstruction Of Microalgal Suspension Absorption Spectra From Reflectance Spectra Of The Cells Deposited On Gf/F Filters

In this communication we present an approach for reconstruction of suspension absorption spectra of microalgae as measured in standard 1-cm spectrophotometric cuvettes from reciprocal reflectance, R(lambda)(-1), spectra of cells deposited on glass-fiber filters. Reciprocal reflectance exhibited the highest dynamic range (eight times wider in comparison with the functions -log(T) and -log(R)) and showed almost linear relationships with suspension absorbance and chlorophyll content from 0.7 to 9.9 mu g/ml. The relationships between suspension absorbance and the -log(T) and log[(1-R)/T] functions were non-linear and were fitted by second-order polynomials with high contribution of the quadratic term. The use of R(lambda)(-1) allowed the reconstruction of suspension absorbance of six species from key groups of planktonic microalgae in the range from 0.001 to 0.250, with RMSE < 0.02. The advantages of the suggested approach over traditional techniques employing -logT(lambda) of the filters are discussed, including the suitability for plankton studies in the field and for the monitoring of cultivated microalgae.