Characterisation of cyanobacteria and their metabolites by fluorescence spectroscopy

In situ fluorometers have been examined for their potential to provide early warning of bloom development via the analysis of fluorescent cell pigments to give an estimate of cell biovolume. Despite the potential for monitoring algal blooms using fluorometers, there has been no in-depth study that analyses the broad spectrum of fluorescence associated with algae, from pigments through to the AOM exudates, using 3-D excitation-emission matrix (EEMs) spectroscopy. Hence, in this study, the evolution of fluorescent algal cell pigment and AOM characteristics over time for a wide variety of cyanobacterial and algal species was investigated using EEMs as a function of the growth phase, cultivation methods and simulated environmental conditions. The AOM released by key cyanobacterial and algal species were studied at lab scale throughout their growth using 3D-EEMs combined with Parallel Factor analysis (PARAFAC). Monitoring of algal population at source and drinking water treatment plant was also investigated. A six-component PARAFAC model was developed for the analysed dataset. Comparisons of the different AOM revealed that major differences in character were associated with the presence of fluorescence at wavelength pairs of 290:345 nm (tryptophan-like region) and 355:475 nm (humic-like region) which had significant correlations with DOC and dominated across the exponential and stationary phases. Distinct AOM character differences between algae and cyanobacterial species were also evident. For example, the AOM of Chlorophyll vulgaris was rich in amino acid-like materials while that of Microcystis aeruginosa was dominant with humic-like substances. Environmental variables had a significant effect on the pigment content and released AOM character during the growth phase studied. Similarly, the variability of fluorescent AOM in the field and through drinking water treatment processes was dominant within the amino acid-like region, humic-like region (Peak C) and humic-like region (Peak A). This led to the conclusion that cell pigment and AOM fluorescence vary as a function of biotic and abiotic factors and its in-depth understanding and application for real-time monitoring will help improve current monitoring tools