The identification cation of phytoplankton pigments from absorption spectra

The absorption spectra of photosynthetic algae are characterized by a conti nuous envelope, which is a result of the overlapping spectra of the indivua l pigments. This feature makes it difficult to estimate the contribution of each pigment to the total absorption spectra. Derivative analysis is an ob jective tool for isolating absorption peaks in phytoplankton. Theoretically , electrons and ions of interacting molecules can be regarded as simple har monic oscillators in an electromagnetic field, which result in a Lorentzian shape. However, when measured by an optical spectrophotometer the signal i s transformed into a Gaussian curve. Thus, a combination of both types of c urve provides a realistic approach to the decomposition of absorption spect ra. In this study derivative analysis is performed on absorption spectra in order to prove that the method can be successfully used to identify the in dividual absorption spectra of component pigments. The spectra used are mod elled phytoplankton, spectrophotometric measurements of algal cultures and samples from natural waters. A combination of Gaussian-Lorentzian shaped cu rves, centred on the identified peaks, were compared with the original spec tra and showed good agreement.