Coral Fluorescence

 Couple of days ago I had a visiting diving instructor ask me if I had ever seen the coral fluorescence. Confused, I asked him if he meant the plankton bioluminescence, only to have him repeat “coral fluorescence.” As you can already tell, I had never experienced such a thing. He went on to explain that if we went on a night dive he had the blue light that shows the coral fluorescence, just like you see the highlighter colours under UV light. Intrigued, I asked him if he was available the following night to go diving!

As we prepare to get in the water I start adjusting my camera because I am so excited to get a few shots of this once-in-a-lifetime experience, however, I was missing a very important part of the camera equipment, the yellow filter, which allows you to see more of the fluorescence in the pictures. I brought the camera anyways in the hopes that I would get at least one decent shot.

We entered the water with our normal diving torches, and began to sink down, we observed the creatures that come out at night, which were mentioned on the Creatures of the Night post, until we got to an area with good coral coverage. We put away our torches and the blue light came on, then all you could hear was my “OH MY GOSH” underwater sound, followed by my instructor’s giggles.

Not all the corals fluoresce, but the ones that did really put you in a state of amazement. The very intriguing part was that they not only they fluoresce in different colours, but the structures of the polyps which sometimes are unnoticed, really stick out. I was able to easily see the tentacles and the centre mouth of the polyps present in certain small corals.

Now, you are probably wondering how this happens. According to Roth et al. 2013 coral fluorescence has been known for quite a while (of course somehow I had never come by this fact, until now), this occurs due to the fluorescent proteins which absorb higher energy light and then emit lower energy light. The reason to “why” corals fluoresce is still unknown, but several hypothesis have come up, from camouflage, antioxidant activity, to photoprotective properties. However, it has been proposed that this fluorescence property may aid in indication of deleterious activities, as fluorescence decreases under higher levels of stress.

The more you think you know, the more you find out that there is still so much to learn!

By: Dayanne Raffoul

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