Corals glowing to survive

Published online 20 July 2017

Biologists uncover how fluorescent corals survive at low-light depths.

Biplab Das

The proteins that give some species of corals their fluorescence also help them continue photosynthesis even when light is low.
The proteins that give some species of corals their fluorescence also help them continue photosynthesis even when light is low.
© E. Smith
Corals in sunlit shallow waters usually glow because of specific proteins that block the sun’s harmful rays. But in dark, deep-water environments, instead of blocking sunlight altogether, those proteins help the corals absorb some light to make food with the help of an algae called zooxanthellae. 

This adaptation is how corals thrive at great depths, according to a new study by a team of international scientists including a first author from New York University Abu Dhabi, United Arab Emirates. 

The scientists explain how the function of the glowing proteins changes in corals, depending on where they live. The corals in poorly lit environments use a special type of red fluorescent protein that captures blue light and re-emits it as orange-red1. This orange-red light penetrates deeper into the coral’s tissue, helping the algae photosynthesize2.

“Our study supports the notion that symbiotic corals living at greater depths have evolved sophisticated adaptations to the challenges imposed by the special light environment,” says primary investigator Jörg Wiedenmann, senior lecturer of biological oceanography at the University of Southampton. 

Corals and algae are locked in a symbiotic relationship. Corals provide the algae with shelter, carbon dioxide and nutrients and in return, the algae supplies 90% of the corals’ energy needs.  

The researchers simulated a dim environment in an artificial coral aquarium and revealed that the red fluorescent corals have a better chance of long-term survival compared to their non-pigmented counterparts. 

The findings matched the distribution of corals in the Red Sea; the corals carrying special red fluorescent pigments are more abundant at greater depths.

This research is greatly significant as it uncovers the mechanisms by which corals can live in these deep-water environments, says marine biologist Christian Voolstra, who studies Red Sea corals at the King Abdullah University of Science and Technology (KAUST), Saudi Arabia and who was not involved in the research. “One of the hopes is that these deeper coral reefs can serve as refugia for corals that are threatened by the consequences of environmental change at lower depths.” 

However, "we need to assess whether all corals have the specific fluorescent proteins to thrive at low-light depths," Voolstra adds. 

These findings could go well beyond conservation too. Glowing corals in deeper water may be a potential source for marker proteins for medical research applications such as advanced microscopic imaging, says Wiedenmann. 


  1. Bollati, E. et al. FRET-mediated long-range wavelength transformation by photoconvertible fluorescent proteins as an efficient mechanism to generate orange-red light in symbiotic deep water corals. Int. J. Mol. Sci. (2017) 
  2. Smith, E. G. et al. Acclimatization of symbiotic corals to mesophotic light environments through wavelength transformation by fluorescent protein pigments. Proc. R. Soc. B. (2017)