In the absence of light under the deep sea lie corals of glowing colors.

Scientists at the University of Southampton in the UK and Tel Aviv University and Interuniversity Institute for Marine Sciences (IUI) in Israel, along with an international team of researchers, discovered corals exhibiting rainbow-like colors, deep in the reefs of the Red Sea.

The group of scientists examined these colorful corals and published their findings in the journal PLOS ONE. They are looking forward to the possibility of developing imaging tools applicable to the field of medicine, through the pigments of the corals.

"These fluorescent pigments are proteins. When they are illuminated with blue or ultraviolet light, they give back light of longer wavelengths, such as reds or greens," said Jorg Wiedenmann, Professor of Biological Oceanography and Head of the University of Southampton's Coral Reef Laboratory.

He believes it is the optical properties of the corals that may significantly turn them into tools for biomedical imaging applications. Living cells or cell structures of interest, for example, can be highlighted by the fluorescent glow of the corals, under a microscope. Wiedenmann adds that the corals may probably be used to detect cancer cells, or in screening for new drugs.

Discovered at about 50 meters deep in the sea, the corals were found to show off fluorescent colors like green, yellow or red. Up in the shallower parts of the reef, corals are seen to exhibit only fluorescent pigments of green. The researchers did not expect to find the more colorful ones lying deeper below.

"Corals from these so-called mesophotic reefs are less well studied since they are beyond the depth limits of standard Scuba diving techniques," said Gal Eyal, a Ph.D. candidate at the IUI. It was through modern developments in technical diving that they were able to explore the waters at greater depths.

Eyal also adds that a reason why they did not expect to see red colors in the deep is because only the blue parts of sunlight can seep through such depths in the waters. Not because of light, but because of fluorescent pigments, the corals display a mix of colors.

Southhampton Senior Research Fellow Dr. Cecilia D'Angelo confirms this, saying that in a number of shallow corals, the amount and color of incidental light tightly control pigment production. In the deep sea, however, the coral's production of pigments is independent from exposure to light.