Blue-green algae (cyanoprokaryota) are a type of phytoplankton, microscopic plants that can cause highly visible algal blooms in both marine and freshwater environments. The algae can have toxic properties, which are referred to as cyanotoxins. Scientists from the EU-funded Cyanoit project examined the correlation between capacity for toxin production and environmental factors. This was achieved by using computer models and laboratory simulations of environmental factors to investigate toxin production. The tests were also conducted using the enzyme-linked immunosorbent assay (ELISA) and physicochemical high-performance liquid chromatography (HPLC). Project partners employed key indicators to determine water quality, which included species composition, abundance and biomass of the phytoplankton sampled. Particular emphasis was given to cyanoprokaryota and algal blooms were determined by measuring biomass and density. Selected bodies of freshwater were examined for the presence of cyanotoxins and found to have relatively low levels of phytoplankton, with relatively few species of cyanoprokaryota present. Researchers also studied 11 Bulgarian reservoirs and dams to determine the levels of heavy metals in the water body. Results showed that the most commonly found raised levels of heavy metals were for zinc lead and cadmium. In one reservoir the level of lead sampled was 30 times greater than the maximum permitted concentration of 0.01 mg/L set by the World Health Organization (WHO). Results from the Cyanoit project underlined the importance of continuous monitoring and control of water quality by evaluating harmful freshwater algal blooms and mapping water bodies at risk. The initiative therefore made an important contribution towards ensuring safe potable water for the people of Bulgaria.