Final answer:
Phycobiliproteins allow cyanobacteria to utilize red light for photosynthesis, giving them an ecological advantage in deeper aquatic environments over green algae. These pigments, alongside chlorophyll a, are significant in cyanobacterial photosynthesis and in contributing to Earth's oxygen-rich atmosphere.
Step-by-step explanation:
Phycobiliproteins are accessory pigments found in cyanobacteria that allow these organisms to photosynthesize effectively under different light conditions than green algae. Cyanobacteria use phycocyanin and cyanophycin as secondary photosynthetic pigments in addition to chlorophyll a, which is also found in plants and algae. These pigments are located in special structures called phycobilisomes and thylakoid membranes, enabling cyanobacteria to utilize a broader spectrum of light, including red light that penetrates deeper into the water column, giving them an advantage in certain aquatic environments.
The phycobiliprotein pigments allow cyanobacteria to perform oxygenic photosynthesis like plants, and their ability to utilize different light wavelengths can give them a competitive edge over other algae in various habitats. This trait, in conjunction with their internal thylakoid structures and historical contribution to Earth's oxygen-rich atmosphere, underscores the ecological importance of cyanobacteria.