MICROCYSTIN-PRODUCING CYANOBACTERIA IN BIOFILMS FROM THE LITTORAL ZONE OF LAKE BAIKAL

Some species of cyanobacteria synthesize toxins, whose concentration during water bloom can reach values dangerous to human and animal health. Planktonic cyanobacteria are the most common and well-studied producers of microcystins – hepatotoxic cyclic heptapeptides, whereas microcystin-producing benthic cyanobacteria are less known. In recent years, the mass development of benthic cyanobacteria forming extensive fouling on different substrates has been recorded in the littoral zone of Lake Baikal. We found microcystins produced by benthic cyanobacteria in the biofouling inhabiting different substrates, including diseased and dead endemic sponges Lubomirskia baicalensis and Baikalospongia spp., collected from the littoral area of Lake Baikal. Microscopic analysis of the biofouling revealed prevalence of Nostocales and Oscillatoriales cyanobacteria with the dominance of Tolypothrix distorta that is likely the main microcystin producer in Lake Baikal. According to enzyme-linked immunosorbent assay (ELISA), microcystin concentrations in biofouling were 29.8–3050 μg/kg dry weight. We identified eight microcystin variants using MALDI-TOF/TOF; [Dha7]MC-YR being recorded in most samples. The presence of microcystins in biofilms formed on the surface of the artificial substrate by Phormidium autumnale was also recorded. The data obtained show the necessity to monitor potentially toxic species and concentrations of cyanotoxins in plankton and benthos in the littoral zone of Lake Baikal, especially in the regions with intense tourist and recreational activities.

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