Differentiation of Algae Clones on the Basis of Resonance Raman Spectra Excited by Visible Light

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Abstract
Fourteen algae clones belonging to four different classes, including clones of Pseudo-nitzschia (Bacillariophyceae), some of which are capable of producing the toxin domoic acid, have been studied by means of resonance Raman spectra excited at 457.9 and 488 nm. Spectra taken at both excitation wavelengths are of high quality and are sufficiently distinct to differentiate clones at the algal class level. All spectra contain major features near 1000, 1153, and 1523 cm-1, which are strongly resonance enhanced due to carotenoid pigments. Weaker features between 920−980 and 1170−1230 cm-1, also due to carotenoid pigments, are more characteristic of the algae clones and more directly reflect different carotenoid composition. Similarities and differences among spectra have been analyzed by the method of principal component analysis (PCA). A distinct clustering of spectral data according to algal class has been shown by PCA score plots. All Pseudo-nitzschia clones can be separated from other classes of algae on the basis of spectra, but it is not possible to distinguish toxic Pseudo-nitzschia from nontoxic clones on the basis of these spectra, which reflect only differences in carotenoid composition.