Study of the Distribution of Phytoplankton and Potentially Toxigenic Cyanobacteria in the Largest Reservoirs of the Kirov Region (Russia) Using Remote Sensing and PCR Analysis Methods

Earth remote sensing data were used to calculate the normalized differential algae index (NDAI) and compile digital maps of the two largest reservoirs in the Kirov region—Belokholunitskoye and Omutninskoye—which are used for cultural, domestic, and recreational purposes. NDAI calculation results were used to analyze the spatial and seasonal distribution of phytoplankton within the reservoirs and identify areas of algae blooms. It was noted that the NDAI varied from 0.10–0.30 in areas not subject to algal blooms to 0.70–0.80 in areas of intensive phytoplankton development during the summer-fall season. Visually, algal blooms in the reservoirs were observed at NDAI > 0.60. Fourteen species of cyanobacteria were identified in the phytoplankton of the reservoirs. Their total abundance ranged from 0.008 to 14.8 million cells/L at different sites, with biomass ranging from 0.0007 to 1.55 mg/L. For the first time molecular genetic methods where used to search for potentially toxigenic cyanobacteria. Successful amplification of mcyE and anaC gene fragments in planktonic DNA samples confirmed the presence of cyanobacteria hazardous to humans, potentially capable of producing microcystins and anatoxin-a. Genetic markers for production of cylindrospermopsin and saxitoxins were not detected in cyanobacteria from the studied reservoirs. Probable cyanotoxin producers include species of the genera Microcystis, Dolichospermum, Aphanizomenon, and Cuspidothrix.