What blue pigment in cyanobacteria is used for photosynthesis?

What blue pigment in cyanobacteria is used for photosynthesis? Phycocyanin is the blue accessory pigment cyanobacteria use to capture light for photosynthesis. It is a phycobiliprotein that works alongside chlorophyll rather than replacing it.

Phycocyanin absorbs orange and red light, with C-phycocyanin absorbing especially strongly near 621 nanometers. Its energy is passed through phycobilisomes—light-harvesting structures attached to the thylakoid membrane—to reaction-center chlorophyll, where photosynthetic electron transfer begins.

Cyanobacteria are sometimes called blue-green algae, but they are bacteria, not true algae. Their ability to perform oxygenic photosynthesis helped transform Earth’s atmosphere. Phycocyanin contributes blue-green coloration and is also useful to scientists as a marker for estimating cyanobacterial biomass during freshwater blooms.

Phycoerythrin is the related red phycobiliprotein and can also occur in some cyanobacteria, so the two names are easy to confuse. Bacteriorhodopsin is a light-driven proton pump found in some microbes, but it is not the characteristic blue photosynthetic accessory pigment named in this question.