Why do deep-sea corals glow?

By AG STAFF 6 July 2017
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Coral and algae form a symbiotic relationship reliant on sunshine. But deep under the sea, light isn’t in abundance, so for a long time the corals survival has perplexed scientists.

DEEP-SEA CORALS, unlike shallow-water corals, which fluoresce to block light, use fluorescent proteins to absorb light in order to assist symbiotic algae and bacteria that satisfy the coral’s energy needs, a new study has found.

The study explains how the symbiotic algae can obtain the light needed to continue to photosynthesize under low-light conditions, through the presence of a special fluorescent protein.

Coral and its symbiotic algae, in this case, zooxanthellae, work together. The algae is provided with shelter and nutrients, while the algae is the basis for 90 per cent of the corals energy needs. Both rely on sunlight.

A team of scientists from the Interuniversity Institute for Marine Sciences of Eilat , the University of Haifa in Israel and the University of Southampton (UOS), determined to understand how deep-sea corals glow, simulated a deep-sea light environment in a coral aquarium.

By analysing the different colours of fluroescent glow and how well these shone through layers of algae, the researchers found that corals are able to survive in such deep waters because of a fluorescent protein, which scientists observed, created blue light and re-emitted an orange-red light.

glowing coral

(Image Credit: Wiedenmann)

“This is an important step forward in understanding how the mysterious fluorescent pigments in corals work. Our finding help us to understand how the amazing diversity of coral colours structures the communities on coral reef,” explained Jörg Wiedenmann, the head of the Coral Reef Laboratory at the UOS.

Emma Camp, marine biologist and climate change scientist at the University of Technology Sydney told Australian Geographic that increasingly, we’re learning that corals can flourish in sub-optimal, that is— less-than desirable environments.

“Such systems have been proposed as potential refuges for future corals as shallow reefs are degraded world-wide. However, the work by Wiedenman shows that deeper corals need special proteins to survive in the extreme low-light conditions,” Emma explained.

“Shallow-corals may not have the features needed to survive in low-light, deeper waters, and as such, these systems may not be able to act as a refuges for corals as environments change,” she said.

“Uncovering mechanisms that support coral survival is crucial to furthering our understanding of how corals may, or may not, be able to survive under environmental change.”

The findings were published in the journal The Royal Society.

glowing coral

(Image Credit: Wiedenmann)