Because of climate changes cyanotoxins have become as an emerging risk in recent decade due to their release from blooms in water bodies of toxic microalgae known as cyanobacteria. Proliferation of cyanobacteria is connected with increased amounts of nitrogen and phosphorus. Temperature also has a favorable effect on the growth of microalgae, which causes their widespread multiplication with the onset of climatic changes in increasing the temperature of water bodies. Cyanotoxins are harmful for human health and environment because they are hepatotoxins, neurotoxins, dermatotoxins, etc. The paper is a summary of data from studies of water collected in the period 2017–2020 from the Bistritsa dam in terms of species composition, algal toxins and nutrients. Bistritsa dam is used for recreation and fishing. Five water samples were tested, microcystins were detected in one water sample from 2020 (microcystin-LR concentration 22.82 µg/l and microcystin-YR 14.05 µg/l in the autumn season). The content corresponds to increased values of the concentrations of the studied nutrients (total nitrogen and total phosphorus 16.81 µg/l and 0.57 µg/l respectively). A bloom of the blue-green alga Anabaena solitaria was also found in the same sample. Regarding the saprobic/trophic status, the water body maintains a permanent beta-saprobic state corresponding to oligo-mesotrophicity. The presence of anatoxin-a was detected in 4 samples with highest concentration 0.4 µg/l. Cylindrospermopsin was nof found in the collected samples. The results show that the investigation of cyanobacterial blooms and the water quality of the reservoirs like Bistritsa dam are important for human health and environmental protection.