Cyanobacteria are algae that live in body of water, and can manufacture their own food. In certain conditions these algae can proliferate fast. This is called Cyanobacteria bloom, and it can become toxic and damage the ecological balance of the body of water. There are several accepted chemical and biological treatments to reduce the bloom. One of these treatments is the addition of special dye to the body of water, which blocks the light transmission through the water.
Watch the following video demonstrating the effect of dye addition to water on their light transmission:
During February 2016, Cyanobacteria bloom was observed in Lake Kinnert.