<P> Cyanobacteria have been found to play an important role in terrestrial habitats . It has been widely reported that cyanobacteria soil crusts help to stabilize soil to prevent erosion and retain water . An example of a cyanobacterial species that does so is Microcoleus vaginatus . M. vaginatus stabilizes soil using a polysaccharide sheath that binds to sand particles and absorbs water . </P> <P> Some of these organisms contribute significantly to global ecology and the oxygen cycle . The tiny marine cyanobacterium Prochlorococcus was discovered in 1986 and accounts for more than half of the photosynthesis of the open ocean . Many cyanobacteria even display the circadian rhythms that were once thought to exist only in eukaryotic cells (see bacterial circadian rhythms). </P> <P> "Cyanobacteria are arguably the most successful group of microorganisms on earth . They are the most genetically diverse; they occupy a broad range of habitats across all latitudes, widespread in freshwater, marine, and terrestrial ecosystems, and they are found in the most extreme niches such as hot springs, salt works, and hypersaline bays . Photoautotrophic, oxygen - producing cyanobacteria created the conditions in the planet's early atmosphere that directed the evolution of aerobic metabolism and eukaryotic photosynthesis . Cyanobacteria fulfill vital ecological functions in the world's oceans, being important contributors to global carbon and nitrogen budgets ."--Stewart and Falconer </P> <P> While contemporary cyanobacteria are linked to the plant kingdom as descendants of the endosymbiotic progenitor of the chloroplast, there are several features which are unique to this group . </P>

When did blue green algae appear on earth