Black algae

摘要

Many species of cyanophytes, especially those growing on tiles and walls exposed to air and sunlight, appear black due to the presence of pigments in the mucilaginous cell-walls. Such pigments may serve a protective role against adverse effects of ultraviolet light but, overlying the ordinary intracellular blue-green pigments, they make the algal clumps look black. Among the most familiar of such algae are species of Gloeocapsa, which by discolouring pale surfaces of public or private premises can constitute a nuisance responsible for a considerable loss of financial value.