Coral Color: Pale, Chlorophyll And Other Pigments

2023 Author: Molly Page | [email protected]. Last modified: 2023-08-25 12:41

There is a common misconception among new to hobbyists that if a coral changes color, the coral is sick. Most often, color change occurs due to the adaptation of corals to new conditions, new lighting.

There are many natural causes for a coral to change color, but the most frequent and dramatic changes depend on the light the coral receives. The quality of radiation includes: intensity, spectrum and amount of ultraviolet radiation. By reacting to light, certain cells in the coral that absorb light and the pigments that protect the coral can change. As a result, a balance of cells and the amount of pigments is achieved, which are responsible for the health and nutrition of the coral.

Millepora, or stinging coral (Millepora)

Color changes from light intensity

Corals are able to adapt to different light intensities. Corals contain symbiont cells containing chlorophyll called zooxanthellae. The coral provides these cells with protection, and they in turn provide the coral with nourishment from photosynthesis. The number of these cells and the amount of chlorophyll varies with the intensity of the light, thus constantly providing the coral with the nutrients it needs. If the light intensity is higher than what the coral is accustomed to, some of the symbiont cells will leave the coral, or their chlorophyll content will decrease. Excessive light exposure poses a hazard to the coral, as zooxanthellae produce excess oxygen. Oxygen in large quantities is harmful to corals.

On the other hand, when the light is too low, zooxanthellae are unable to produce the nutrients the coral needs. In this case, the number of symbionts will increase, as will the content of chlorophyll in them.

The color change depends on the number of symbiont cells and the content of chlorophyll in them. The color of these cells ranges from golden yellow to brown. They turn brown when there are more such cells than the coral needs. In other words - the less light - the darker these cells. On the other hand, if a coral is placed under a light source, some of the symbiont cells will simply leave their host, giving the coral a paler coloration.

Red coral, photo photography underwater world

Color changes depending on the light spectrum

The light spectrum affects the coloration of the coral. Some colors, such as fluorescent red or orange, cannot be seen during the day, however, they become very pronounced under photochemical lighting. Using lamps with different spectra of different systems will give different color effects on the same corals. Conventional systems for saltwater aquariums contain 50% white and 50% blue photochemical light. In this way, fluorescent colors are provided by a certain wavelength. All this gives the aquarium a natural look.

Color changes depending on ultraviolet radiation

Ultraviolet light is made up of three components - UV radiation A, B and C. We will not consider C radiation, since these rays cannot be created under artificial conditions and they do not penetrate the earth's atmosphere. A and B radiation are light waves that penetrate the surface of the water, are filtered and represent the light that breaks through the water. A and B radiation can destroy DNA and RNA, harming corals. However, many coral species have adapted to this radiation. Corals produce special pigments to protect against it. These pigments are colored blue, purple or pink. Most corals containing these pigments live in shallow water, where the radiation density reaches its maximum. Aquariums commonly use glass metal halide lamps,reflecting ultraviolet light before it enters the water. It is important to protect corals lacking such pigments and to protect shallow water corals that have lost their pigments during transport. It is natural for corals with vibrant colors to lose their pigmentation as they adapt to UV rays. This is not a sign of coral disease at all - it is a normal adaptive response to new conditions.