Invited Paper IPF-TuM3
Coral Fluorescence Imaging

Tuesday, October 21, 2008, 8:40 am, Room 312

Fluorescence in corals is optical alchemy, a magical transformation of ultraviolet or blue light to a rainbow of intense hues. Many marine organisms exhibit vivid fluorescence effects, a marvel of physics in action. Photography of coral fluorescence produces images of striking beauty that are also of great value for science. The biological function of the proteins that are the source of the fluorescence is not yet known, although there is no shortage of hypotheses – an aid for photosynthesis of the symbiotic algae, a sunscreen to protect against excessive ambient light levels, a way to preserve and intensify color in the wavelength-limited underwater environment, a beacon for prey. Photographs taken on the reef provide valuable clues that contribute to the scientific sleuthing. Whatever the function of fluorescence for the corals themselves, the phenomenon is a boon for reef science. Juvenile corals are very small (on the order of 1 mm) and are next to impossible to find in the complex surroundings of a reef. By diving at night with the right equipment many of these small corals can be excited to glow brightly, making them easy to find against the darker background. But not even reef scientists want to do all their work at night, and techniques have been developed to find and photograph fluorescing corals in the daytime without special shading. Corals are not the only marine organisms that fluoresce. The more scientists look, the more examples they find over a wide taxonomic range. In some cases the fluorescence signatures are distinct, and work has been done to perform computer classification of seafloor scenes based on the RGB representations of the fluorescence. Imaging is playing an important role in understanding the significance of fluorescence in the marine environment, and in putting the phenomenon to practical scientific use.