Coral pigments and their properties are a common topic of debate within the scientific community, with the bulk of our understanding having been gained in the past decade. Recent science has only started to unveil what function these fluorescent pigments serve, and there is debate over how they originate. Unlike terrestrial plants and most other marine life, coral can contain pigments that give off a fluorescent glow. Despite these anomalies, the rest of coral’s pigmentations function much like any other object our eyes perceive with color.
Before delving into fluorescent pigments and the wavelengths that affect them, it is first crucial to have a basic understanding of the color spectrum coral interacts with and what effect it has on the human eye. The human eye is only capable of perceiving wavelengths on the electromagnetic spectrum between 400-700 nm, and this is also the light we see interacting with coral under natural conditions. The 400 nm end of the spectrum corresponds to the color blue and has a short wavelength, while the 700 nm side corresponds to the color red and has a longer wavelength. All objects absorb some part of the spectrum and reflect the rest, with the reflection being what our eyes translate into color.
The interactions between a coral’s pigments and light waves are controlled by the depth at which the coral is living. Blue spectrum light penetrates salt water better than red spectrum light, leading to enhanced or dulled coloring, depending on which wavelengths the coral is absorbing.
In theory, coral in shallow water will appear more red, because red light wavelengths are able to penetrate the water and reach the coral, reflecting more red spectrum light to the human eye. In deep water, the opposite will be true. With less light in the 600-700 nm range reaching the coral, less red spectrum light is available for reflection, causing the eye to focus on the shorter wavelengths. Of course, variant conditions, such as the makeup of a coral’s pigments, can change the colors we perceive.
Fluorescent pigments are where we start to find variations in coral’s color that do not follow the rules of the conventional light spectrum. When coral with fluorescent pigments receives a certain spectrum of light, often between 445-455 nm, the light will be absorbed and converted not into heat energy, but into another wavelength that falls on the longer end of the color spectrum. This is what gives some coral its psychedelic glow.
Due to its underwater environment, coral has adapted to grow best using light from the blue end of the spectrum in photosynthesis, and because of this, most fluorescent coral will glow green or red. Science is in agreement on how fluorescents work, but not why they exist in coral’s pigmentation.
Recent arguments made in the scientific community assert that coral contains fluorescent pigments in order to protect itself, or potentially its symbiotic brethren zooxanthellae, from damaging light rays. Several scientific studies1,2,3 have come to similar conclusions that coral’s fluorescent glow is a protective measure resulting from its own pigmentation adapting to the light spectrum to which it is exposed. Because of the symbiotic relationship coral and zooxanthellae share, the fluorescent pigmentation is theorized to act as a dual defense mechanism.
As our knowledge of light wavelengths and their impact on coral has improved, our ability to build aquarium-based reefs has, as well. Creating a stunning display of glowing coral while still maintaining a healthy environment for it to flourish is very possible with the correct lighting equipment. If you’re in the market for a reef lighting system that will make your tank thrive, contact us. We’re here to make sure your coral is as dazzling as it is healthy.