A Magical Nighttime Journey Through a Fluorescent Reef

A coral reef is a world of kaleidoscopic shape and color. To see one at night, illuminated by its own fluorescence, is even more marvelous still.

This luminous parade was filmed off the coast of Egypt by Lynn Miner and Steffen Beyer, the founders of FireDiveGear, who custom-build photographic equipment for marine biologists and other undersea explorers.

Miner and Beyer dive in the blackness of night, with the only illumination coming from their own lights. These shine at a wavelength betwen 450 and 470 nanometers, a blue hue that is the only wavelength to penetrate below the sea’s upper waters.

In a sense, FireDiveGear’s lamps mimic sunlight as it’s experienced by life at those depths, only much, much brighter. With the right filters, it’s then possible to see what happens when light shines on reef dwellers. Their pigments become excited and emit photons, the phenomenon known as fluorescence.

“If you hit them with intense blue light, they shine back in purple, yellow, green, red, all the different colors,” explains Miner. “You don’t see those colors if you’re diving with a white light.”

As Al Dove on Deep Sea News describes, the biological function of fluorescence isn’t certain. Depending on the creature, it could have some purpose tied to the visual sensitivity of marine organisms to fluorescent light.

Deep-sea fluorescence could also be a fluke, a coincidental side-effect of other photochemical processes. All that’s certain is that fluorescence, what biologist Mikhail Matz of the University of Texas at Austin calls “the secret color of the deep,” is gorgeous.

“It’s an alternate universe. It’s abolutely a whole other world,” said Miner. “These stunningly beautiful creatures, the colors of these tropical fish — it’s hard to imagine. It’s hard to describe how beautiful they are, the brightness, the diversity.”

Like many divers, Miner is dismayed by the state of coral reefs in the early 21st century. Disease outbreaks, rising temperatures and human development threaten corals around the world.

Read more at Wired Science