RSEC Fluorescence Night Dive (Blue Light Night Dive)

Fluorescent reef – glowing corals

Cnidarians can be stimulated to glow in the night. This was discovered in 1927 by the British scientist Charles Phillips during one of his daily beach walks. Phillips noticed a peculiar shimmering colour of sea anemones in intertidal pools. Many coral species gleam in bright colours, as they can transform invisible light into visible light as well. The bright colours formation is based on a physical and chemical phenomenon called fluorescence.

During fluorescence, special pigments (proteins) absorb the short wave, energy rich (UV-) radiation and redistribute it nearly simultaneously –although with a higher wave lenth that that which lies in the visible spectrum – and with a loss of energy. This wavelength shift is called Stokes shift. Based on the wavelength shift it is possible to explain several phenomenons on the reef, e.g. a fish still retains his red signal colour at a depth of 15 m. In fact, the amount of red light in these depths is significantly lower than the surface, yet special pigments will emit red light.
Certain zoooxanthellate (algae housing) corals are able to thrive below the euphotic zone through auto-fluorescence. In the Gulf of Aqaba, the zooxanthellate coral Leptoseris fragilis has been found living at a depth of 145 m – depth in which no photosynthetically active light can penetrate. Though, specific pigments in the coral tissues catch the remaining short-wavelength light. This light is then transformed into light more efficient for photosynthesis (light with longer wavelengths).

The RSEC offers in joint collaboration with several dive centers diving with special blue lights (these are not UV-lamps; they do not harm the corals!). Divers can experience the reef in glowing fluorescent light during these special dives. There is no good or adequate description for the colours and the general appearance of reef organisms under blue  light. Sea pens and small tube-dwelling anemones are perceived more often through Blue light than through normal white light. “Blooming” corals with open polyps as well as tube worms appear in a beautiful gleam. Many scientists have dealt with the fluorescing properties of corals, anemones and jellyfishes since the first discovery of this phenomenon. It appeared that many cnidarians fluoresce in green, blue, yellow and red colours and that this glowing originates mostly from special protein structures.

Experience this for yourself! A description in purely words will always be a far cry from the beauty of this phenomenon. Come and see it with your own eyes.

Fluorescence Night Diving is offered at following dive centre: Sinai Divers Backpackers, Sinai Divers Hilton, Extra Divers Dahab and INMO Divers Dahab