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Eleven genera of blue-green algae are reported from chasmolithic, cryptoendolithic and hypolithic habitat of semiarid/arid regions of Africa, North America, Australia and Europe. Included are photobionts of lichens of the families Lichinaceae and Peltulaceae, which belong to the blue-green algal genera Chroococcidiopsis, Cyanosarcina, Gloeocapsa and Myxosarcina. Species of these unicellular genera were also the dominant free living microorganisms in the chasmolithic and cryptoendolithic habitats. Species of the genera Chroococcopsis and Cyanosarcina are new records for the lithobiontic habitat.

A strain of Chroococcopsis was isolated from the lower surface of quartz pebbles from the Namib Desert. This is the first record of this genus from a terrestrial habitat, where it was associated with rocks. The two earlier described species of the genus were only known from aquatic habitats. In vivo absorbance spectroscopy revealed an UV-B absorbing substance in the isolated strain.