Chlorophyll d is a form of chlorophyll, identified by Harold Strain and Winston Manning in 1943. It is present in marine red algae and cyanobacteria which use energy captured from sunlight for photosynthesis. Chlorophyll d absorbs far-red light, at 710 nm wavelength, just outside the optical range. An organism that contains chlorophyll d is adapted to an environment such as moderately deep water, where it can use far red light for photosynthesis, although there is not a lot of visible light.