Cyanobacterial water blooms as an environmental hazard to waters

Abstract

The article describes and analyzes the problem of cyanotoxin contamination of water bodies in Ukraine and other countries of the world. Eutrophication of water bodies, which is caused by human activity, climate change lead to uncontrolled development of cyanobacteria, and thus to ecological danger in hydrosphere objects. Anthropogenic eutrophication (increasing the content of nutrients in water due to their introduction into water bodies during pollution of water bodies by flood and municipal runoff, fish farming use of water bodies), temperature rise, increase in carbon dioxide content in the atmosphere, as a result of the transformation of introduced organic matter in water, contribute to increasing the dominance of cyanobacteria in water ecosystems. Bloomforming cyanobacteria produce various neurotoxins, hepatotoxins, and dermatotoxins that can be fatal to birds and mammals (including waterfowl, cattle, and dogs) and threaten the use of water bodies for public water supply, recreation, irrigation, and fishing. Among the toxins of blue-green algae, nodularin, saxitoxin, microcystin, domoic acid, guanitoxin, anatoxins and others were found. Exceeding the critical mass of algae and their metabolites activates the selfdecomposition process. This leads to the removal of oxygen from the water, and instead the release of methane, hydrogen sulfide, ammonia, and other toxic substances. The result of this is not only the death of fish. Cyanobacteria are capable of natural genetic transformation — genetic change of the cell as a result of direct absorption and inclusion of exogenous DNA from its environment. A sufficiently effective solution to the issue of controlling the activity of cyanobacteria is the use of humic preparations. it was established that humic substances (humic acids, fulvic acids) in certain concentrations negatively affect the growth, development and activity of cyanobacteria. Humic substances, as a component of organic matter and a reserve of organic carbon in its global cycle, have a negative effect on hydrobionts by increasing their concentration in water bodies. However, humic substances are able to regulate the activity of phytoplankton. The introduction of humic substances at a concentration of 2-5 mg/l of reservoir water significantly affects the activity of phytoplankton (suppresses phytoplankton vegetation, reduces the slime formation of cyanobacteria, and, from the beginning, inactivates the synthesis of cyanotoxins). This effect is provided by the alkaline pH of humates, high content of iron and copper.