or blue-green algae Any of a large group of prokaryotic, mostly photosynthetic organisms. Though classified as bacteria, they resemble the eukaryotic algae in many ways, including some physical characteristics and ecological niches, and were at one time treated as algae. They contain certain pigments, which, with their chlorophyll, often give them a blue-green colour, though many species are actually green, brown, yellow, black, or red. They are common in soil and in both salt and fresh water, and they can grow over a wide range of temperatures, from Antarctic lakes under several metres of ice to Yellowstone National Park's hot springs in the U.S. Cyanobacteria are often among the first species to colonize bare rock and soil. Some are capable of nitrogen fixation; others contain pigments that enable them to produce free oxygen as a by-product of photosynthesis. Under proper conditions (including pollution by nitrogen wastes) they can reproduce explosively, forming dense concentrations called blooms, usually coloured an opaque green. Cyanobacteria played a large role in raising the level of free oxygen in the atmosphere of early Earth
The smallest plankton (< 0 2 µm) blue-green algae are abundant in the oceans and sometimes in freshwater Their outer membrane is very hard to digest; not many larger plankton eat them until that membrane is destroyed by a few species of bacteria and virus They also may form large algae cluster mats
are aquatic, photosynthesizing bacteria They are often called "blue-green-algae," but are not algae Cyanobacteria generated the oxygen atmosphere that we breathe today Their fossils are the oldest on the planet
One of the ancient bacteria with a blue pigment, phycocyanin (similar to blue-green algae) They also contain chloroplast like other green plants Cyanobacteria are aquatic and photosynthetic
predominantly photosynthetic prokaryotic organisms containing a blue pigment in addition to chlorophyll; occur singly or in colonies in diverse habitats; important as phytoplankton