A Glow in the Deep

Corals are actually large colonies of tiny animals called polyps that build massive skeletons that form reefs. In order for corals to survive they depend on the single celled algae that grow inside them called "zooxanthellae." These algae provide the corals with food and energy through photosynthesis, while the corals provide nutrients and a safe environment for the algae.

There are several theories about why corals might have these fluorescent pigments. One is that they may be protecting the corals from bright light in shallow water. Mazel says that in dimmer conditions, the fluorescence process may take colors of light that are not useful for photosynthesis and convert them. Ackleson thinks its possible that corals are trying to communicate through their fluorescence. "In general", he says, "any plant or animal is highly colored for one of two reasons: they are either trying to attract organisms that are beneficial to them or they are trying to ward off other organisms that could be harmful to them." And he thinks corals may have evolved with these fluorescent pigments "to develop a relationship with those kinds of organisms".

Potential applications

Mazel, who is also the founder of a company called NightSea, has developed equipment for viewing and imaging fluorescence. He, Ackleson, and other navy divers have been diving with a laser imaging system fitted with lights and filters. When the seafloor is illuminated with blue light, and yellow-filters eliminate as much of the non-fluorescent light as possible, the corals fluoresce the brightest. The imaging system also allows them to measure the color and intensity of the fluorescence.