Although a majority of these algae are indeed some shade of red, a wide variety of colours from yellow through blue to almost blackish hues are exhibited by various species. This colour variation results from the dominant accessory pigments phycoerythrin (red) and phycocyanin (blue), which mask the blue-green of chlorophyll a. Red algae absorb green, blue and red portions of the light spectrum and store fixed carbon in the form of floridean starch.
Unlike most other algal types, red algae have no motile reproductive stages—a factor that has not hindered their amazing proliferation. The cell walls of some red algae contain the complex polysaccharides agar and carrageenan, which have important commercial applications as emulsifiers and stabilizers in various food and industrial products.
Approximately 90 percent of the nearly 6,000 species worldwide live in the marine environment, and this group contains the deepest-dwelling alga—268 m (884 ft) for one Caribbean species. Approximately 370 Pacific Northwest red algae—many of which have attractive branching forms—are documented. The photograph features an undetermined species.