Cyanobacteria are phytoplankton organisms, which can be found in all types of water bodies worldwide. Places with their excessive occurrence are water environments rich with plant nutrients, spread from temperate to tropical areas. Their excessive proliferation and mass occurrence is described by cyanobacterial blooms.
Cyanobacteria can overcome unfavourable conditions as spores in the sediment of the lake bottom. During the favourable conditions, they can proliferate a lot and very often prevail. Their most distinctive advantage over other phytoplankton organisms is the content of phycocyanins. These auxiliary photosynthetic pigments allow for efficient use of low light intensity, which other algae and plants are not able to exploit. An additional advantage are gas bubbles in their vacuoles, which can regulate their position in the water column, enabling the best use of light and nutrients.
The majority of genera of cyanobacteria form cyanotoxins, which belong to the most dangerous toxins. The evidence of toxicity of cyanobacterial population in a given water body does not necessarily mean greater danger for the environment or people as long as the population is small and evenly dispersed. The real threat occurs only at the mass occurrence, especially in the form of surface blooms and scums. The cyanotoxins are being released continuously during the growth stage of the bloom and are massively released after the collapse of the cyanobacterial bloom.
The toxic blooms of cyanobacteria threatens the health of humans, animals and the environment. The appearance of large cyanobacterial masses is inappropriate also from the aesthetic point of view, reduces the opportunity for recreational activities, is the source of unpleasant odours and give a repulsive taste of drinking water when obtained from such polluted source.