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The use of multi-spectral Fluorescence Induction and Relaxation technique for physiological and taxonomic analysis of phytoplankton communities

Maxim Y. Gorbunov*, Evgeny Shirsin, Elena Nikonova, Victor V. Fadeev, Paul G. Falkowski

*Corresponding author:

ABSTRACT: Unlike terrestrial plants, phytoplankton are extraordinarily diverse, comprising thirteen phylogenetic groups, with diatoms, dinoflagellates, and haptophytes being among the most prominent eukaryotes in the modern ocean. Development of sensor technologies for rapid taxonomic and physiological analysis of phytoplankton communities is crucial for ecological monitoring programs in the global ocean. Here we describe a novel, ultra-sensitive, multi-spectral Fluorescence Induction and Relaxation instrument (a mini-FIRe) and examine analytical capabilities of this technique for rapid determination of phytoplankton taxonomic groups, together with physiological characteristics and photosynthetic rates. We collected and analyzed the database of spectral and photosynthetic properties of major taxonomic groups of phytoplankton. Our research revealed that the spectral shape of the functional absorption cross-section of PSII, σPSIIex), is remarkably constrained within each major phylogenetic group of eukaryotic phytoplankton, including diatoms, haptophytes, dinoflagellates, and chlorophytes. Variability in σPSIIex) within each group was found to be significantly smaller than the difference between individual groups. In addition to σPSIIex), we also examined the classical excitation spectra of Chl-a fluorescence yields, Fmex). Our comparative analysis revealed that σPSIIex) is a better and more specific proxy for taxonomic analysis. For instance, our developed σPSII-based algorithm correctly identified 90% of experimental data, while the Fm-based algorithm - only 77%. Our results suggest that the multi-color variable fluorescence analysis offers a promising tool for the combined physiological and taxonomic analysis, including identification of major phyla within the “red” lineage of eukaryotic phytoplankton.