What accessory pigment gives red algae their red color?

What accessory pigment gives red algae their red color? Phycoerythrin is the main accessory pigment responsible for the characteristic red appearance of many red algae. It belongs to the phycobiliprotein family, a group of water-soluble pigments that gather light for photosynthesis.

Phycoerythrin absorbs wavelengths of light that chlorophyll absorbs less efficiently, especially blue-green and green portions of the spectrum. Its chromophore, commonly phycoerythrobilin, gives the protein-pigment complex its strong red coloration. The captured energy is transferred through phycobilisomes to chlorophyll at the photosynthetic reaction centers.

Red algae also contain chlorophyll a, along with carotenoids and other phycobilins. Their pigment mix can produce shades ranging from pink and purple to deep red or nearly black, depending on species, environment, and depth. The pigments are located in phycobilisomes attached to the thylakoid membranes of their chloroplasts.

A common confusion is with phycocyanin, another phycobiliprotein that appears blue and is especially associated with cyanobacteria. Fucoxanthin, by contrast, is the accessory pigment most strongly associated with brown algae and many diatoms.