Natural History

They Only Come Out at Night

When the sun sets on the coral reef, a different cast of characters comes out to play.

By Suzanne Gerber ~ Photos & Captions By Barbara Shively

Like the denizens of Lady Gaga’s demi-monde, the creatures who come out at night on the coral reef are a psychedelic parade of colors, shapes and textures. A nighttime visit to the reef is an entirely different experience than what you find during daylight hours. Hard corals that resemble stones by day become flamboyant showgirls by moonlight, as they shimmy and shake their boa-like tentacles to feed in the evening sea. Like nocturnal club kids, critters that are shy and elusive in the stark light of the sun let their hair down after dark. Introverted cliques of cardinal, squirrel and soldierfish become wild and wooly under cover of darkness. Crustaceans as a group are almost totally transformed. Reclusive crabs, octopi and certain species of lobsters come out of their closets to cruise the reef in search of dinner, a midnight snack, or perchance just a surreptitious hook-up.

Giant star coral and orange cup coral

Giant star coral and orange cup coral

Barbara and I have both had quasi-religious experiences on night dives. One of the most awesome experiences of her life occurred on a “dark of the moon” night dive (a few days after a full moon, when that heavenly body doesn’t rise till late evening) off Grand Turk. During the briefing, the group was told that at the end of the dive they were to gather together, switch off their lights, and wait on the sandy bottom. She recalls being a bit nervous, yet she trusted her divemaster. After a minute or two, when her eyes had adjusted to the pitch darkness, she beheld a vision that looked to her as if the sky had fallen and landed on the ocean floor. The longer she sat there, the more “stars” she saw. They were so close it seemed as if she could reach out and touch them. “If you can imagine sitting in the middle of the sky surrounded by millions of stars, you begin to get the idea what we were feeling,” she says, adding that she’s had that experience several times since, “and the magic never lessens. This is impossible to capture with a camera — regrettably — but it is an image I will carry in my mind forever.”
Regal slipper lobster foraging after dark

Regal slipper lobster foraging after dark

What Barbara and her dive buddies were seeing was the bioluminescent plankton that float in the water — like underwater fireflies. Marine biologists estimate that 90% of all sea creature emit some form of bioluminescence. Under certain conditions, you can actually sit in a boat, wave your hand through the water, and watch the water light up. When you’re diving, you learn early on to briefly hold your dive light over your gauges, and when you remove it, the dials glow in the dark. Bioluminescence—for my fellow language geeks — comes from the Greek word bios (“living”) and the Latin lumen (“light”).
Scrawled filefish sleep at night without changing colors

Scrawled filefish sleep at night without changing colors

I’ve done plenty of night dives in the TCI, which are stunning because of the amazing clarity of the water. But my first-ever night dive was in Cozumel, and like many first-timers, I approached it with great trepidation (“What if my batteries die?” “What if I lose you guys?” “What if I don’t see something and it bites me?”). Yet I had heard such incredible things and was determined to tough it out. We hit the water just before the sun was setting. It was warm and calm, and we landed in a shallow sandy patch just in time to see a long-legged crab strutting his stuff across the shoal. As the light dimmed, we finned around and found a fearless octopus, presumably out for dinner. But first she was determined to give us a show: changing colors and gliding over small coral heads and letting us stroke her preternaturally soft body — normally a big no-no for divers! Later in the dive, a precious, box-shaped trunkfish literally swam into my hands and wouldn’t leave when I tried to push him away. I “handed” him to my dive buddy, who had the same experience. We actually keep little “Trunkie” with us for the entire dive. Never since have I had an experience to rival that.
Caribbean octopus hunts its prey at night

Caribbean octopus hunts its prey at night

One of the things that’s so different about diving at night — aside from the obvious fact that the only light comes from your torch — is that your attention becomes focused on the objects in your beam of light. Fewer distractions makes it easier to concentrate on the wonders of the individual and the minuscule — like a rare orange-ball corallimorph or a tiny decorator crab perched on a soft coral, or the delicate tentacles of an orange cup coral — as Barbara did in the photos that accompany this story.
Rare photo of Golden Crinoid walking at night along a vertical wall

Rare photo of Golden Crinoid walking at night along a vertical wall

At night, under the color-correcting light of a dive torch, hues appear brighter and more vibrant. That’s because during the day, the ambient light filters out the brighter colors as they penetrate increasing depths of water. As divers, we learn that underwater, we “lose” colors according to the Roy G. Biv spectrum, meaning red is the first go. (If you’ve ever pricked your finger underwater, you’ve probably noticed that your blood looks green.) Thanks to Barbara’s strobe, the red encrusting sponge seen on page 63 is appreciably more impressive-looking than it would be in ambient light; ditto colorful regal slipper lobster on page 61.
Channel Clinging crab munching on dinner in spite of diver's light

Channel Clinging crab munching on dinner in spite of diver's light

But night photography has its challenges, as Barbara has experienced time and again. Lights attracts tiny krill by the hundreds and they will bounce off your hand as they jockey for a spot close to the light source. Barbara likes to tell about the time she pointed her beam directly at the center of a giant basket star, a critter with arms that stretch a foot or more in every direction. “It’s a heady experience to behold a swarm of krill invading your light as the basket star goes into a feeding frenzy, waving and curling its tentacle in an attempt to corral the krill into its ‘mouth,’” she says. “You almost don’t know where to point the camera.”
Observing the reef at night teaches us things we’d never learn if we only dived during bank hours. I was amazed to witness, for instance, about the “shift change” that happens as the light of the sun begins to fade. The half hour or so between light and dark is called “quiet time,” and it’s like trying to hail a cab in Manhattan at 4 PM, just as all the drivers are heading home. There’s next to no activity on the reef. But wait! Soon a whole new crew comes on-duty, as the brightly colored diurnal fish turn in for the night. If you don’t know what to expect, you’re in for a real treat, as Barbara was the first time she encountered feathery crinoid at night. She’d been seeing them for years, waving their tentacles out from under the edges of corals and sponges, and she naturally assumed they were anchored in that spot for all eternity. Then one night she did a dive along a vertical drop off Grand Turk and spotted a golden crinoid strolling along the wall!
Another discovery that always excites visitors to the nighttime reef is the unique sleeping environment of the parrotfish. This perennial favorite excretes a mucus bubble in which they tuck themselves, cocoonlike, to sleep. This mucus “sheath” not only protects the fish from predators by shielding its scent, but it also serves as an early-warning system when a predator approaches. (And now some researchers believe that the parrotfish’s mucus has antibiotic properties that help repair bodily damage.)
Similar but different — Barbara and I have both heard that dawn is also an incredible time to dive. The night shift is packing it in, and the early birds are just waking, ready to begin another busy day on the reef. From all descriptions, it sounds like a magical time to be down there. (In fact, we’ve talked about doing this together for a future article.) But if there’s one thing divers treasure — because the trip could be our only real vacation of the year —is staying cocooned in our own little mucus bubbles as long as we can. Let’s just say it’s on the docket, and although Barbara insists I answer, “Don’t hold your breath.”

New York-based Suzanne Gerber writes about scuba, travel and health for a variety of publications.

Avid underwater photographer Barbara Shively discovered Grand Turk diving in 1997 and has returned every year. It is her passion to share the coral reefs’ beauty through her photographs, many of which can be viewed and purchased at http://shivelygallery.com. A variety of her prints are on sale at Art Provo, located in The Regent Village, Providenciales.



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Hobbyist photographer and Assistant Director for Research & Development at the TCI Department of Environment & Coastal Resources Dr. Eric F. Salamanca took this rare photo of a Bahama Woodstar hummingbird enjoying the nectar of Moringa flowers.

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