Use of fluorescence fingerprints for the estimation of bloom formation and toxin production of Microcystis aeruginosa.

The development of methods facilitating the detection of cyanobacterial blooms in drinking water reservoirs at an early stage is of great importance. Fluorescence spectroscopy could meet these requirements. The study contains the examination of possible correlations between the different maxima of a fluorescence excitation-emission matrix and the amount of produced and excreted toxins of a lab culture of Microcystis aeruginosa at different stages of growth. Various fluorescence signals (protein-like and humic-like substances, pigments) are suited for an estimation of cell density and actual intra- and extracellular toxin concentration. One signal at 315nm/396nm presumably originating from protein-like substances might be useful as a tool for the prediction of increasing cyanobacterial toxin concentrations. As the measurement of fluorescence matrices is still time consuming, synchronous scans with Deltalambda=80nm were tested as a potential alternative. They accurately depict the course of protein-like and humic-like fluorescence during the different stages of growth although especially the latter one is not captured at its maximum. However, due to insufficient separation of chlorophyll a and phycocyanin, the image of the matrix maxima by synchronous scans with Deltalambda=80nm can only be used with minor restrictions. Nevertheless, fluorescence spectroscopy seems to be a powerful tool for the evaluation of cyanobacterial blooms.