Abstract
Delayed fluorescence (DF) excitation spectroscopy is a fast in vivo method to determine phytoplankton composition in freshwaters using the signature of photosynthetically active pigments which is characteristic in each algal class. Four classes could be distinguished: green algae (including Chlorophyceae, Euglenophyceae and Conjugatophyceae), chromophyte algae (including Bacillariophyceae, ...
Abstract
Delayed fluorescence (DF) excitation spectroscopy is a fast in vivo method to determine phytoplankton composition in freshwaters using the signature of photosynthetically active pigments which is characteristic in each algal class. Four classes could be distinguished: green algae (including Chlorophyceae, Euglenophyceae and Conjugatophyceae), chromophyte algae (including Bacillariophyceae, Chrysophyceae and Dinophyta), Cryptophyta and cyanobacteria. The DF excitation spectra of various cyanobacteria species were investigated with the aim of improving the reliability of the results obtained by DF. Exposing cyanobacteria to different ambient light conditions did not significantly influence the shape of DF excitation spectra. However, the DF excitation spectra of different cyanobacteria species showed different signatures: a high species-specific variability of the ratio phycocyanin (PC):phycoerithrin (PE):allophycocyanin (APC) derived from DF excitation spectra was observed. This variability has to be taken into account when using DF to determine phytoplankton composition in freshwaters dominated by cyanobacteria. The quality of the fits could be significantly improved by using calibration spectra of cyanobacteria species which are, according to their spectral features, at least similar to those species present in the investigated water body.
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