Small Bioluminescent Jellyfish. Photographer: M. Youngbluth Credit: OAR/National Undersea Research Program (NURP); Harbor Branch Oceanographic Institution

Light, one of life’s essential ingredients. We use it’s energy, use it to see, It affects the majority of our lives. Imagine a world without it…

Deep down in our oceans, there is a on-going party, occurring 24 hours a day. This underwater disco is an exclusive event, with only organisms with a unique talent able to participate.

The must-have talent is bioluminescence!

A chemical reaction occurring at the cellular level within an organism can cause this colourful spectacle. The reaction occurs when certain chemicals are mixed together (see reaction below),  the reaction then creates an ‘explosion’ of bioluminescent light.

Luciferin + O2   –>  Oxyluciferin + CO2 + Light


Bioluminescence occurs in terrestrial organisms too! But just a fraction of terrestrial organisms rely on this colourful glowing gift. But descend into the deepest depths of the ocean and you’ll find between 80-90% of creatures in the deep use bioluminescence.

Due to the depths involved, scientists find it hard to find and study these wonderful creatures.


Zones within our oceans

To understand why Bioluminescence is used in the deep ocean we must first understand how light penetrates through the depths of our oceans. (Fig.1)

At sea level we have what is known as the Euphotic zone, which is also known as the sunlight zone. This zone is approximately 200 meters deep, only a small amount of light can travel beyond this zone.

Between 200-100 meters we have the Dysphotic zone, which is also known as the twilight zone. As depth increases within this zone, light decreases and photosynthesis is no longer an option for creatures within and below this zone.

Any depth below 1000 meters is called the Aphotic zone, which is also known as the midnight zone. 0% of the suns light is able to penetrate below this zone. Organisms have to find a way to adapt to this harsh environment.

illustration of how far light travels in the ocean.
(Figure.1) Photic zones within our oceans. Credit: NOAA ocean service.


Why Bioluminescence?

Due to the lack of light within the midnight zone, animals use bioluminescence for several different reasons.

The main reason, as seen in Dinoflagellates, is attraction. Whether it be attracting a mate, like the male Caribbean Ostracod, which uses bioluminescent ‘indicators’ to light up its upper lips to attracts a female. Or even attracting a potential victim to your mouth like is seen in the Angler fish, which uses bioluminescent bacteria in a ‘lure-type’ appendage which dangles in-front of its mouth, attracting potential prey to their certain demise. Other examples of attraction for the purposes of feeding include the Stauroteuthis syrtensiswhich uses a bioluminescent ‘ring’ of bacteria around its mouth to once again, attract prey to their death.

Small fish appearing to spit out bioluminescent Dinoflagellates. Credit: Unknown; Image: imgur.com

Another reason for using bioluminescence is defence. Swima bombiviridis, which is known as the “green bomber”, is a small polychaete worm which releases a ‘bomb’ of bioluminescent light in order to foil any potential predators attack. Other forms of defence include counter-illumination, which is used by the Firefly squid, Watasenia scintillansWhich produces bioluminescent light on the underside of its body in order to camouflage itself with light coming from the surface of the sea.


Why we should care about bioluminescence..

You may have sat reading this and thought to yourself, how does this affect us as humans?

We currently live in a world that is heavily reliant on burning fossil fuels to meet our energy demands. Bioluminescence may hold the answer to unlocking a greener future. Research is currently underway into the use of genetically modified plants that produce light, eliminating the need for any sort of electricity to power it. No copper wires, no fossil fuels burned, just a bioluminescent chemical reaction within the organism.

Other uses for Bioluminescent light are also currently being researched too, not just ones that help our ever growing reliance on unsustainable energy. Water purity is also tested with genetically modified bioluminescent microorganisms. Cancerous cell tracking is also made easier by the use of bioluminescent bacteria!

As you can see, we are in the early years of research and many exciting developments await as we develop new and innovative uses for the this incredible natural wonder.

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