Mystery of Coral Fluorescence Solved

Much that goes on in the dark depths of the ocean are still a mystery. That said, curious researchers have now succeeded in figuring out the answer to something that has befuddled scientists for years: Why do corals glow?


Glowing coral in deep waters
Coral glowing in dark waters | Tel Aviv University

Scientists have known for a long time that corals that dwell 148 feet below the ocean’s surface, in what is called the twilight mesophotic zone, glow a radiant green or orange around their mouth area (yes, they have mouths!) or on the tips of their tentacles.


Coral experts have also known that corals give off light after they absorb energy. This is called biofluorescence - not bioluminescence, which is an effect created by a reaction between an enzyme and a light-releasing molecule.


What researchers didn’t know was why corals at this depth glow. Some of their best hypotheses are that the fluorescence protects the corals from heat or light after bleaching (something like sunscreen for corals) and that the fluorescence somehow moves the process of photosynthesis along.


However, researchers from the School of Zoology, the Steinhardt Museum of Natural History at Tel Aviv University, and the Inter-University Institute for Marine Sciences in Eilat postulated an alternative theory: What if the corals glow to attract prey?


The scientists then set about testing their hypothesis with a three-step study and were able to prove their theory was correct.


“Despite the gaps in the existing knowledge regarding the visual perception of fluorescence signals by plankton, the current study presents experimental evidence for the prey-luring role of fluorescence in corals,” explains study leader Dr. Or Ben-Zvi of Tel Aviv University. “We suggest that this hypothesis, which we term the ‘light trap hypothesis,’ may also apply to other fluorescent organisms in the sea, and that this phenomenon may play a greater role in marine ecosystems than previously thought.”


All new knowledge about corals is important and will better help and inform scientists and conservationists in helping protect coral systems - for enhancing biodiversity and for future generations to marvel at and enjoy.

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