For a long time, cyanobacteria were considered incapable of performing non-photochemical quenching (NPQ) as a photoprotective mechanism, relying instead on a mechanism of energy redistribution between the two photosynthetic reaction centers, PSII and PSI, known as "state transitions".
OCP is found in a majority of cyanobacterial genomes, with remarkable conservation of its amino acid sequence, implying evolutionary constraints to preserve an important function.  Mutant cells engineered to lack OCP photobleach under high light and become photoinhibited more rapidly under fluctuating light.  Under nutrient stress conditions, which are expected to be norm in marine environments, photoprotective mechanisms such as OCP become important even at lower irradiances.
This protein is not found in chloroplasts, and appears to be specific to cyanobacteria.