What Makes Corals Glow?
Imagine this: you are diving through the crystal-clear water when suddenly the reef lights up. An array of purple, pink, orange, and green hues dances across the reef in a spectacular show. What you see is one of the ocean’s most mesmerizing displays - coral fluorescence.
But what exactly causes these underwater light shows in the oceans, and why do corals glow in reef aquariums?
As scientists have recently discovered, the answer is far more fascinating than any reef hobbyist or coral enthusiast imagined. These glowing coral displays are not just beautiful forces of nature, but they are survival strategies, millions of years in the making.
The Science Behind Coral Fluorescence
Before we dive in, we should note that when corals “glow,” they are actually fluorescing, not bioluminescing. The difference? Coral fluorescence happens when the coral absorbs light at one wavelength and emits it at another. Corals absorb shorter wavelength light (like UV and blue light) and emit it as longer wavelengths that we see in vibrant and colorful hues.
This glowing phenomenon is a biological process that involves specialized proteins called fluorescent proteins. These protein molecules are like tiny light transformers, taking the abundant blue light that the ocean water penetrates, and converting it into a spectacular array of colors that make coral reefs look vibrant. This is why coral reef tanks look better with blue lighting!
For years, scientists were stumped by how corals could fluoresce. They knew how corals glowed, but the mystery behind why they did it was a mystery. Many factors floated around the scientific community - maybe it was protection against harmful radiation, or perhaps it helps corals undergo photosynthesis. In 2022, scientists at Tel Aviv University and Scripps Institution of Oceanography cracked the code with groundbreaking research that revealed the truth - corals glow to hunt. These scientists found that corals use their fluorescent displays as fishing lures to attract prey.
Coral Fluorescence: Beyond Hunting
Coral fluorescence serves many purposes beyond luring prey. Scientists have found at least four different functions for coral’s glowing proteins.
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Light Enhancement
Corals use fluorescence to make the most of the lighting available. They can convert dim blue light into red and orange wavelengths that their symbiotic algae (zooxanthellae) can use more efficiently for photosynthesis.
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Biological Sunscreen
In shallow water where light is most intense, the corals utilize their fluorescent proteins to act as a biological sunscreen. They absorb harmful blue and UV light that could damage their tissues and zooxanthellae, and emit the light as less harmful, longer wavelengths.
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Immune Defense
Some fluorescent proteins help boost the coral’s immune system by neutralizing pathogens and parasites.
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Antioxidant Protection
During photosynthesis, harmful free radicals are created as a byproduct. The coral’s fluorescent proteins help neutralize the cellular radicals, protecting the corals.
Coral Fluorescence in Reef Aquariums
Understanding how and why corals fluoresce has revolutionized how we approach reef aquarium lighting. When corals glow brilliantly under blue actinic lights in reef aquariums, you are triggering the same biological processes that occur in the ocean.
In the ocean, blue light in the 400 to 490 nanometer range is what penetrates the deepest. It is also the primary wavelength that activates coral fluorescence. When blue LED aquarium lighting was developed, manufacturers focused on recreating the natural light environment that corals have evolved in over millions of years.
Why Does Blue Aquarium Lighting Make Corals Glow?
Blue aquarium lighting mimics the deep ocean’s natural lighting. Corals have learned to grab blue lighting and use it for fluorescence, as this light is what reaches deeper coral communities in the ocean.
When blue lighting is switched on in reef aquariums, the blue photons from the lighting fixture hit the coral’s specialized fluorescent proteins, causing them to emit the longer wavelengths that create stunning purples, pinks, greens, and oranges that we discussed earlier.
Aquarium Lighting For Maximizing Coral Fluorescence
To maximize coral fluorescence, aquarium lighting should have a wide-band-blue spectrum, between 400 and 500 nm.
At Reefco Aquariums, we offer the EcoTech Marine RADION XR30 G6 BLUE LED LIGHT FIXTURE, specifically engineered to deliver richer colors, enhanced fluorescence, and the ultimate balance between crisp and actinic lighting. This cutting-edge 6th-generation fixture pushes the limits of color rendition and fluorescence with the addition of 395nm diodes that reach deeper into the UV range, achieving unprecedented levels of coral and fish fluorescence.
The G6 features a revolutionary Hybrid Hemispherically Edge Illuminating (HEI2) optic system that provides mind-blowing spread with an impressive 126.3-degree output angle, ensuring incredibly even PAR distribution across almost 4 feet of coverage area. This wide, even spread means fewer fixtures are needed to cover more tank space, making it one of the most efficient aquarium lights available. The enhanced optics also utilize your aquarium's interior glass to reflect light back into the tank, reducing shadowing and providing illumination to the undersides of corals.
While blue lighting is key for fluorescence, other wavelengths such as white and white-blue combinations are equally important for coral health and growth. The RADION G6 delivers a fully programmable, intense full spectrum with wireless control capabilities, moonlight simulation, and weather effects, allowing you to create the perfect lighting environment tailored to your specific coral requirements.
Conclusion
The research behind what makes corals glow is extremely exciting. Scientists are now looking into coral restoration techniques that take advantage of coral fluorescent signaling to help bleached coral reefs recover faster. Also, as aquarium lighting continues to evolve, new LED aquarium lighting systems are being designed to support both coral growth and coral’s complex fluorescent biology.
If you would like to learn more about coral fluorescence or what aquarium lighting is best for your reef aquarium setup, contact the Reefco Aquariums team for our recommendations and expert advice!
