Stony coral fluorescing green underwater, photographed at night using blue coloured flashlight and a yellow filter. Surrounding algae glow orange. Blue light excites pigments within some underwater organisms causing them to emit a fluorescent glow. This coral also harbours symbiotic algae which require light to photosynthesize and produce nutrients. It is thought that in shallower waters, the fluorescent pigments in such organisms act as a sunscreen that prevents too much ultraviolet light damaging the algae. In deeper waters and lower light levels, it is thought that the fluorescent pigments absorb ultraviolet light and emit it at a wavelength which promotes photosynthesis in the algae. Photographed in the Red Sea, Egypt.
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