Cyanophytes can be found in every type of environment including marine, freshwater and terrestrial habitats. They can also be a part of lichens and can be found in mosses! 

Even if they can be harmful, they play a key role in aquatic food webs by being grazed on by zooplankton. Cyanos can be colonial or unicellular and are among the most diverse group of prokaryotic organisms, we owe them aerobic life on this planet!