By Kuhu Bhattacharya
What goes on under the sea? Is there a source to power bulbs for light? A little-appreciated fact is that most of the animals in our ocean make this very light. This phenomenon is called bioluminescence. The prodigy takes place through every level of the oceanic bubble - from the surface to the deep seafloor. It is not a rare occurrence as one might think, rather, it takes place in a large variety of creatures ranging from minute bacteria to sizable sharks.
Deep-sea creature exhibiting luminescence.
How does bioluminescence take place?
Luciferin is the chemical reaction initiated by a molecule reacting with oxygen to produce light, causing bioluminescence. The presence of promoters and catalyst enzymes such as luciferase and photoprotein (a protein active in the emission of light by a living creature) aid in the formation of glowing light. Bioluminescent creatures have developed the ability to enhance light production through physiological, molecular, anatomical, and behavioral adaptations. The wavelengths of the color green and blue travel the farthest underwater which is the reason for its larger visibility and emission in the sea. Though there are certain species such as fireflies on land that emit a yellow light and fish like black loosejaw give out red coloured luminescence, the occurrence of the same is rather rare.
Firefly exhibiting luminescence on land.
Why and where does bioluminescence occur?
Bioluminescence is typically used to detect prey, warn and distract predators and communicate within the water body. The flash is like a scream for help. It is also called a bioluminescent burglar alarm, similar to the alarm at your house or car - to cast unwanted attention onto the intruder, thereby either leading to the capture or scaring them away. Animals such as whales and squid are attracted to the glowing underside of the cookie-cutter shark, which grabs a bite out of the animals once they are close. The deep-sea anglerfish lures prey straight to its mouth with a dangling bioluminescent barbel, lit by glowing bacteria. Jellyfish use this phenomenon to scare away predators too.
Can we perceive the exact color of bioluminescence?
Photoreceptors present in our eyes visualize which color works best in the presence of bright light. Under the sea, the color insensitive photoreceptors called rods are activated. This is why our eyes cannot accurately perceive the color of the luminescent emission. However, to combat the same, sensitive spectrometers are used by scientists to determine the emission spectrum of the light.
Though bioluminescence may be considered rare if compared by the total number of species, it is extremely diverse in its occurrence. There is a language of light in the deep ocean, and we are just at the beginning of unraveling and understanding it.