What percentage of animals in the open ocean make light?

Nearly 80 to 90 percent of animals living in the ocean make light. Most of the ocean’s bioluminescent organisms live in the twilight or poor light zone. Animals living in this deep zone include jellyfish, squid, shrimp, krill, marine worms and fish.

Although, most bioluminescence organisms are found in the ocean a few can actually be found on land. In fact if you have ever seen a firefly glowing on a summer night than you have seen bioluminescence. Other common organisms on land that emit light are glow worms and some species of fungus.

By combining two types of substances in a chemical reaction bioluminescent organisms release energy in the form of light. The first substance, luciferin reacts with oxygen to produce light. The other, luciferase, is an enzyme that catalyzes (speeds up) the reaction. However, these substances come in many different forms and can vary depending on the species.

The color of bioluminescence produced by an organism can vary from red to violet. Bioluminescent organisms on land most commonly produce the color green since it reflects the best against green plants. In the ocean the primary color produced is blue because it transmits the easiest through seawater.

Although, scientist are still unsure as to why all bioluminescent organisms produce this light typically it is used for communication, locating food, camouflage, attracting prey, and self defense. Fireflies for example use bioluminescence create flashes in specific patterns that are used to attract a mate. A shrimp on the other hand may release bioluminescent light into the face of a predator in an attempt to escape.

If you would like to learn more about bioluminescence in the ocean than we highly recommend watching the excellent video presentation "Glowing Life In An Underwater World" by Edith Widder.