Read an Academic Passage

Bioluminescence in Marine Organisms

Bioluminescence, the production and emission of light by a living organism, is one of the most fascinating phenomena in the natural world, particularly in the deep ocean. This light is generated by a chemical reaction, typically involving a substance called luciferin and an enzyme, luciferase. Unlike a light bulb, this "cold light" produces very little heat. In the perpetual darkness of the deep sea, where more than 90% of organisms are estimated to be bioluminescent, the ability to create one's own light provides a significant survival advantage.

Marine creatures use bioluminescence for a variety of purposes. One of the most common is to attract prey. The anglerfish, for example, dangles a glowing lure in front of its mouth to draw in smaller fish. Another key function is defense. Some squid release a cloud of bioluminescent ink to startle and distract predators, allowing them to escape. This light can also be used for communication, helping organisms find mates or signal their territory in the vast, dark expanse of the deep ocean.

The patterns and colors of bioluminescence can also serve as camouflage. The "counter-illumination" technique is used by many species that live in the twilight zone of the ocean. They produce light on their undersides that matches the intensity of the faint sunlight filtering down from above. This effectively erases their silhouette, making them nearly invisible to predators looking up from below. This sophisticated use of light showcases the remarkable ways in which life has adapted to one of the planet's most extreme environments.