Ocean STEMulation: Uses for bioluminescence

Focusing on science, technology, engineering, and math (STEM), as they pertain to the ocean.

This is part 2 out of 2 blogs on bioluminescence. Read part 1 here

Bioluminescence is extremely useful for many species - but why? 

There are quite a few land species that exhibit bioluminescence – such as certain fungi or insects, the most familiar of which are certainly fireflies. However, the vast majority of bioluminescence can be found in the ocean. By some estimates, 80 to 90% of deep sea creatures can produce light. It is believed to have evolved not just once but many separate times, which indicates that it has major benefits for survival.

Bathocyroe fosteri is a bioluminescent species of ctenophore, or comb jelly. Photo by Marsh Youngbluth via Wikimedia Commons, public domain. 

With this multitude of bioluminescent organisms, also come a wide range of uses for the light. For example, some creatures use it to hunt, like the anglerfish which has a glowing lure to draw in prey.

Others use bioluminescence to avoid becoming prey. You may have noticed dinoflagellates if you’ve ever seen the ocean at night during a red tide – they can make large areas of water glow. They flash when they are disturbed by water movement, and this is believed to help illuminate predators. If a fish swims through the dinoflagellates, all of a sudden the fish will become illuminated, and this exposure can make it vulnerable to other, larger predators.

The glowing dinoflagellates give away the position of prey fish as dolphins dash through the water to round them up. Photo by Ricky Qi via Flickr, Creative Commons License. 

Many predators hunt in the twilight zone by looking upwards, searching for dark shadows against the light surface. But the hatchetfish has blue photophores along its belly and it can match their brightness with that of the surface. With this technique called countershading, it can blend almost perfectly into the background above.

The deeper you go in the ocean, the less light there is. Red is absorbed first and the last light available before it goes pitch dark is blue, so many deep sea animals can only see blue light and often only produce blue light, and animals can use this to their advantage: the stoplight loosejaw fish can produce red light, and it seems that this allows the fish to see others while going unnoticed itself.

A bioluminescent siphonophore drifts in deep, dark water. Down below it is an ROV. Photo by NOAA Photo Library ,IFE, URI-IAO, UW, Lost City Science Party; NOAA/OAR/OER; The Lost City 2005 Expedition, via Flickr, Creative Commons License. 

While we’re used to seeing bioluminescence coming from animals, we aren’t used to it coming from outside them, but one species of shrimp can eject a cloud of bioluminescence when threatened, similarly to how an octopus would squirt ink – the predator is distracted by the cloud while the prey makes a quick escape.

Scientists have additionally found examples of organisms using light for other purposes. For example, some crustaceans have been found to use it for communication and for attracting mates.

In addition to the pure wonder and amazement inspired by bioluminescence, due to its beauty and diversity, it turns out that bioluminescence has practical uses for humans as well. Through the study of bioluminescence and the chemicals that make it, scientists are finding a vast array of uses for it from using the light to detect pollutants in the environment to studying the progression of diseases like cancer.

See stunning images and learn more about this amazing phenomenon by watching this video: 

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