1. They help in reclamation of alkaline soils.
2. They have heterocysts, which are helpful in the fixation of atmospheric nitrogen.
3. They release o2 in the environment due to their photosynthetic activity.
4. Oscillatoria and few other cyanobacteria can be used as pollution indicators.
5. They have symbiotic relationship with protozoa, fungi, and nitrogen fixing species form associations with angiosperms. They are photosynthetic partner in most of lichen association. Lichens contribute to soil formation.

6. "Super Blue green algae" are basically expensive pond scum in which cyanobacterium is a singled celled organism which produces its own food through photosynthesis. It serves as a "complete whole food" which contains 60% protein with all essential amino acids in perfect balance.

7. Many species of cynobacteria form water blooms, where they often impart unpleasant smell and due to large amount of suspended organic matter water become toxic and causes mortality among livestock. Some species produce toxins that kill livestock and other animals that drink the water.
8. Their ability to photosynthesize and also to fix atmospheric nitrogen means that their nutritional requirements are minimal. They can serve as food for heterotrophs in ecosystems.