You might have seen images on the Internet where living creatures glow with usually cyan, sometimes light green, and yellow light. This light is called bioluminescence and is produced by a living organism. Bioluminescence produces light energy within an organism’s body. For the chemical reaction to occur, an organism needs to contain two molecules: luciferin, which produces light when reacts with oxygen, and luciferase, which is a catalyst to the reaction. The color of the light is the result of the rearrangement of luciferin molecules.

Some of the land creatures like fireflies and fungi can luminesce. However, bioluminescence is mostly found in marine organisms who live in oceans, such as jellyfish, bacteria, sea stars, worms, and even some sharks. Some of the land creatures like fireflies and fungi can luminesce as well. The glowing surface of an ocean you can see in pictures or real life is the bioluminescent plankton (single-celled dinoflagellates) – it can also be called the glowing plankton. The “milky sea phenomenon” is another example of bioluminescence when large surfaces of water are lit up. They can be bright enough to be seen from satellites orbiting the Earth.

Some organisms do not produce luciferin to glow – they absorb it through the food they consume or through a long-term interaction. For instance, squids store the bioluminescent bacteria in their organs. Unlike squids, some types of fish acquire luciferin by eating shrimps.

There are many reasons why bioluminescence exists and is important. Organisms can easily regulate the time of their glowing based on their immediate needs – for example, if they need to mate, hunt, or defend themselves.

When bioluminescence is used as a defense mechanism, some species light themselves up and can flash to confuse their attackers or scare them away. Some use a bioluminescence technique called counterillumination when organisms hide from predators that hunt below by blending in with the light from above the ocean. Some organisms can even detach their glowing body parts to distract the predator. This method is often used by sea stars.

When the glowing is used as a hunting mechanism, the most common example is the anglerfish that we often see in movies. It has huge sharp teeth, a big head, and a filament on top of it that can light up. The bioluminescent light of the anglerfish attracts the prey in deep waters with a complete absence of sunlight.

For humans, bioluminescence can be an art form. Some artists can use bioluminescent bacteria to draw or decorate their paintings. Bioluminescence can also be an interesting topic to study. That is why biochemists, engineers, and others study it to unravel some mysteries about the ocean and perhaps discover something new that could be beneficial to us in the future.