For the identification of ecologically significant dominant groups of phytoplanktonic algae a polychromatic DCMUinduced fluorescence method is recommended. A special fluorometer equipped with a system of replaceable filters is used to differentiate three regions of the spectrum (410 ± 20, 510 ± 20 and 540 ± 10 nm) that can excite the basic light-harvesting pigments. Total and differential (for every algal taxon studied) chlorophyll a calculated from the fluorescence signals is in good agreement with biomass estimates from direct cell counts for several different trophic types of aquatic systems. This is made possible by the vizualization of the ratios of fluorescence signal values in their own coordinates: first, to decide whether it is necessary to correct linear equations in order to eliminate negative solutions; second, to determine the possibility of nulling the negative solution if a point is situated close to a side of the triangle; and third, to reduce the number of linear algebraic equations to two if the points are situated along one of the triangle sides or to one if the points are gathered at the apex. The polychromatic DCMU-induced fluorescence method can be used for monitoring natural phytoplankton populations to detect changes in their taxonomic structure.Abbreviations: DCMU, 3-(3,4-dichlorophenyl)-1,1-dimethylurea; DOM, dissolved organic matter
Microcystis aeruginosa is a well-known Cyanobacterium responsible for the formation of toxic water blooms around the world. Shallow, warm, and eutrophic reservoirs provide the most favourable conditions for M. aeruginosa development. Numerous studies have been devoted to this species, but there still is a necessity to develop additional approaches for the monitoring of cyanobacteria in reservoirs. In this study, M. aeruginosa in the water column of a hypereutrophic Siberian reservoir was investigated by fluorescence, light, and electron microscopy as well as genetic analysis using a mcyE marker. Here, we demonstrate the genetic diversity and features of the fluorescence spectra for different ecotypes of this species. We suggest that a fluorescence approach can be used to identify M. aeruginosa in a natural environment in order to increase the effectiveness of ecological monitoring and water quality evaluation.
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