AZOLE COMPOUNDS AND THEIR EFFECT ON BLOOM-FORMING CYANOBACTERIA
The widespread use of azole compounds as biocides leads to their inevitable release into the environment and water contamination. Many modern azole based agents are toxic and despite the biodegradability, can have negative impact on the aquatic biota. In the present study the effects of azole compounds - 1,2,4-triazole and isothiazolinones, on the development of mass species of cyanobacteria and the synthesis of secondary metabolites was investigated. Unialgal cultures of cyanobacteria Anabaena variabilis, Aphanizomenon flos-aquae, Oscillatoria agardhii, Microcystis aeruginosa, green algae Scenedesmus quadricauda and Oocystis parva were used in experiments. Our research has shown that cyanobacteria are highly sensitive to isothiazolinones compounds, and less sensitive to 1,2,4-triazole. By their sensitivity to 1,2,4-triazole cyanobacteria are comparable to green algae, but are less resistant to the isothiazolinones. In the study of the toxic effect of azole compounds, the impact on photosynthesis of cyanobacteriat was determined. A special role in cell adaptation to toxicants plays phycoerythrin, whose concentration in the presence of 1,2,4-triazole and isothiazolinones increases severalfold. The action of the azole compounds characterized by increase of cell permeability and increased metabolites (odorants and cyanotoxins) release into the environment. The content of odorants in the water remains at a high level even when the growth of cyanobacteria is almost completely inhibited. Despite the inhibition of toxin production by the azole compounds, biomass of toxic cyanobacterium M. aeruginosa retains its toxicity due to the changes in toxin ratio. The ratio changes in favor of the most toxic cyanotoxin - microcystin LR. Thus, contamination of aquatic ecosystems with azole compounds may not only have an impact on the structure and succession of algal community, but also cause an increase in the concentration of harmful cyanobacterial metabolites and degradation of natural waters.