Go for the Glow

The science behind coral colours

- Text by Dr Cecilia D’angelo and Prof. Jörg Wiedenmann

The stunning colours of corals attract many divers to the reefs of the world. The Indo-Pacific region in particular, a hotspot of coral biodiversity, is home to a large number of species with spectacular colours. While the brownish appearances of some corals under daylight is due to the photosynthetic pigments of the symbiotic algae that live in their tissue, most of the green, red and purple-blue hues are caused by a family of protein pigments.

Some of these pigments glow green or red under ultraviolet or blue light, a physical phenomenon called fluorescence. This is a process during which light of a distinct colour is taken up by certain dye particles and subsequently re-emitted with a different, more red-shifted colour. Everyday examples of fluorescent dyes can be found in marker pens or high visibility clothing. The fluorescent coral pigments are all related to the green fluorescent protein (GFP) from Aequorea victoria, which is involved in the bioluminescence reaction of this jellyfish.