Updated: Sep 24, 2020
The fascinating phenomenon that spans from the air to the sea!
Photo: Image from Pixy.org. Labelled for reuse
On a calm night in Mosquito Bay, dimly lit by moonlight, kayakers admire the spectacle that glows beneath their paddles. With each stroke more light is emitted from the waters below, flushing the bay with a radiant blue color. Mosquito Bay in Vieques is known for its breathtaking bioluminescent waters that can be seen after the sun sets. Although other bodies of water are also bioluminescent, Mosquito Bay has the brightest in the world.
But how does bioluminescence work? The water doesn’t just magically glow on its own. There are tiny organisms living in the water that, when disturbed, emit bioluminescent light. In Mosquito Bay, these organisms are Pyrodinium Bahamense, a type of dinoflagellate that glows brighter than many others, making the bay a popular spot for tourism. Many other species also produce chemicals that emit bioluminescent light, and the trait itself has evolved separately at least 40 times! Most are found in oceans, like squids, football fish, and single-celled organisms. Organisms with bioluminescence can also be found on land or in freshwater, although the trait is found most commonly among marine life. An example of a bioluminescent organism you might have seen in nature is the firefly, which uses its ability to glow during the evening time around ponds, lakes, or other open spaces outside.
The term bioluminescence may be more specific than you think. Bioluminescence refers to animals which are able to produce light for a reason beneficial to their survival. Producing light for purposes that aren’t explicitly beneficial to the organism is referred to as biological chemiluminescence. Another misconstrued phenomena is iridescence, which uses external light and can make organisms look shiny and reflect light. You might see this in butterflies or beetles.
Because of the large variety of bioluminescent animals, the chemicals used in creating the visible glow differ based on the organism. Differences in chemical makeup can also be attributed to the separate evolution of many species. Chemicals that emit light when undergoing a chemical reaction are called luciferins. Luciferins tend to vary based on species. Fireflies have one type of luciferin, while fungi and bacteria have another. Luciferins act with luciferase, an enzyme that catalyzes the reaction which produces light.
Animals produce light for a multitude of different purposes. Dinoflagellates, like the ones in Mosquito Bay, glow brightly when disturbed to protect themselves against predators. The glow is meant to attract the attention of bigger predators which will eliminate the consumers of the dinoflagellates, leaving them safe. Bioluminescence can be used for reproductive purposes, and can be a useful tool in attracting a mate. Similarly, light patterning can help indicate the sex of an organism, differentiating males from females. Glowing also shows that an organism can be poisonous, warding off potential predators. Light emission is a scare tactic for survival, helping prey to escape potentially dangerous situations. A quick flash of light can help to intimidate or stun predators and give the prey an opportunity to slip away. Usually this will entail a bioluminescent “bomb”, a pre-prepared collection of chemicals waiting to be set off in case of need for quick action. Squids spray ink to distract a predator, and some organisms even deploy light as a decoy for the predator to chase. Bioluminescence can also be utilized to camouflage, blending in with the color of the ocean or other environment and making it harder for prey to be tracked. Specifically, marine organisms tend to use counterillumination, a form of camouflage, where emitted light mimics the light coming from the surface of the water. By blending into the water, prey mitigates the danger from any predators below. While prey use bioluminescence to escape predators, many predators have their own abilities to help them hunt a meal. This can range from using light to seek out and spot prey, to shock and stun them, and lure them with light.
Bioluminescence has evolved heavily in marine life due to the filtration of light through water. Because the deep sea has very little to even no light, many organisms need to produce their own light to sustain themselves. Luciferins in aquatic species have a blue-green hue, which travels better in water than other light, improving the efficacy of their glow. For land animals, light is more readily accessible, even at night with the moonlight. Contrasting to aquatic luciferins, luciferins in land species tend to have a green, red or yellow hue.
Beyond use for survival and reproduction in animals, bioluminescence has proven to have practical applications in society. A study regarding the amount of bacteria and food remains left on surfaces at a University canteen utilized bioluminescence in tracking the effectiveness of cleaning. Firefly luciferin reacted to ATP, found in living organisms, and used to monitor the presence of bacteria. By measuring the luminosity of a surface, the conductors of the study had a metric for exactly how much bacteria spread there was in a given area and where bacteria would spread given time.
Similar practices are used in the tracking of diseases. Scientists have used bioluminescent light to track the spread of salmonella and the AIDS virus. The light acts as a marker and can help determine where bacteria spread and what antibiotics work to prevent spread.
In the future, bioluminescence may also be harnessed as a replacement for light fixtures. Scientists have experimented with introducing bioluminescent chemicals to plants by having them absorb chemical infused water through the stomata. Plants have been able to glow, but not yet to a degree visible to the human eye. In order to make bioluminescent lighting a possible future, plants would need to contain enough luciferin to produce a visible light. However, luciferin can be damaging to the plant if introduced in extreme doses. Although difficult, finding a middle ground would provide a more ecologically sustainable alternative to modern-day lighting, and open up more opportunities of integrating bioluminescence into modern society.
Bioluminescence has even more theoretical applications. As we’ve seen, bioluminescence can and has been used to make advances in medical research. Another new pathway opened up by the utilization of bioluminescence is the study of biological functions within living animals. In the past, fluorescence has been used in the past to monitor tissue from animals, but processes couldn’t be studied within the animal itself. Utilizing bioluminescence allows examinations to occur without having to kill or excise tissue from an animal, which allows for more information to be gained from a functioning system rather than decaying cells.
Crop testing can be revolutionized by bioluminescence as well. Although there is concern for introducing genetically modified organisms into nature or in food production, studies and experiments have been conducted by researchers into the possibility of having indicator plants to determine the overall needs of crops. Specifically, potatoes were experimented on and modified to indicate dehydration when exposed to black light. Such abilities would allow farming practices to improve and water consumption would be reduced.
The same principle of using bioluminescence as an indicator of a condition can be applied to water contamination testing. Bioluminescent bacteria can be genetically modified to glow when exposed to certain contaminants, creating a safe and viable option to test for many different types of dangerous chemicals.
The many forms, uses, and applications of bioluminescence prove it to not only be an essential and effective method of survival for so many species, but also beneficial to the advancement of modern technology. Whether you are admiring the dinoflagellates at Mosquito Bay, watching fireflies glow in the evening, or researching new cures for diseases, there is a profoundness and importance that can be admired behind the beautiful glow of bioluminescent light.
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