fluorescent diving & snorkeling > coral fluorescence
What is called fluorescence?
Not to be confused with phosphorescence, or bio-luminescence, Fluorescence is the absorption of one wavelength of light (or colour) and the re-emission of another, totally different wavelength of light (or colour). A fluorescent object under white light reveals its true colour. But under near UV light, it absorbs the blue and re-emits a fluorescent colour, transforming the blue into a brightly glowing, totally different colour.
Fluorescence is a member of the ubiquitous luminescence family of processes in which susceptible molecules emit light from electronically excited states created by either a physical (for example, absorption of light), mechanical (friction), or chemical mechanism. Generation of luminescence through excitation of a molecule by ultraviolet or visible light photons is a phenomenon termed photoluminescence, which is formally divided into two categories, fluorescence and phosphorescence, depending upon the electronic configuration of the excited state and the emission pathway. Fluorescence is the property of some atoms and molecules to absorb light at a particular wavelength and to subsequently emit light of longer wavelength after a brief interval, termed the fluorescence lifetime. The process of phosphorescence occurs in a manner similar to fluorescence, but with a much longer excited state lifetime.
Why some marine life get fluorescent?
Which UV dive light is more efficient?
When did we discover this phenomenon?
The first person to talk about this fluorescence phenomenon was Mr Philips in England in 1927. He noticed that the anemonies had this property to reflect green fluo under UV light.
In the 50’s, Luis Marden, noticed this fluoresccence phenomenom when scuba diving as a photographer.
In the 60’s René Catala is the first to really study this phenomenom and to write about his researches. Then Richard Woodbridge III was the first to take UV lights under the water. He publishes as well some articles inherent to the subject.
In the 70’s, Charlie Mazel starts to buil some UV lights. He is the founder of Nightsea!
Around 2000, David Doubilet was famous for his underwater fluo pictures.
Nowadays, Fluorescent night diving is still not very developed and to be honest I don't really understand the reason why apart the fact that the lamps are expensive and available at few manufacturers.
So FEW people have done this experience, BE THE FIRST!
Underwater, marine animals that fluoresce have the ability to convert one colour into an entirely different colour!
On the document on your right you can easily see the difference between colors you will see in day time and colors you will see under UV dive lights.
The true reason for fluorescence in corals remains unclear today, and the reason for fluorescence in more complex creatures is completely obscure. The subject of fluorescence extends all boundaries in understanding and even now remains as controversial in the science community as it is fascinating.
-source: wakatobi diving-
However, there are several theories provided by scientist, and perhaps the most likely reason is that it acts as a kind of “sun block” for the coral protecting the zooxanthallae inside the coral from the harmful rays of the sun.
Marine Biologists say that this property could perhaps protect shallow coral from bleaching or provide deeper coral the ability to absorb the UV light from the sun and reflect it back to the zooxanthallae allowing them to photosynthesize in the absence of sufficient sunlight.
We could notice that our UV lights are working only on coral which is alive hence it is a way to see the healthiness of the reef!
Other fluorescence theories claim that fluorescence is an indicator of the health of coral, or is somehow used to signal coral spawning.
Some scientists have also suggested that the light is used by coral to ward off predators.
In summary, this magic new world is mostly explained by a chemical reaction created by the blue leds that cause some proteins and minerals to fluoresce brightly.
Whatever the reason, for divers and underwater photographers, fluorescence is simply another unique dive experience and photo op.
The wavelength of light used in most fluo torches is a band of blue, somewhere between 440-480 nanometers (depending on the manufacturer).
Researchers have discovered that blue light is more efficient in stimulating green fluorescent protein (GFP) and its mutations, which emit colors other than green.
We find this light a bit more powerful than UV, however you will need to wear a barrier yellow visor which is easy to lost or break.
For fluo diving we can as well use ultraviolet lights (black-light) with sub-400nm range. Some companies produce UV torches for underwater use because invisible UV excitation light has the advantage of requiring no additional filters (no mask wearing).