The presentation explores *Cyanobacteria blooms and cyanotoxin impacts in coastal waters*, addressing the presence of freshwater cyanobacteria and their toxins in coastal environments. It delves into marine cyanobacteria blooms and questions the existence of marine cyanotoxins. The potential biotechnological applications of cyanobacteria are also discussed, showcasing their broader use in research and industry despite the environmental and health challenges posed by these blooms and toxins.