— William Matthews, “Skin Diving”
hardy reef, queensland / 19°44’ s, 149°12’ e /
depth: 10–13 metres / june 2008
Here on Hardy Reef, in soft, refracted light ten metres below the surface of the Coral Sea, the scene is a sort of mystical mix of frenetic and tranquil, like something out of an anthropomorphic cartoon rendering of rush hour with the sound turned down to a soothing, ambient hum. Dense aquatic traffic moves everywhere, constantly, in swarms and tidy lines and tangents, in ever-morphing smears of electric colour, all against a backdrop even more riotously hued and just as busy. The reef wall is a vertical forest of coral branches and squiggles in a hundred shades of Day-Glo, fire-red fractal twists alongside lime-green paisley curls alongside delicate golden folds.
I slow myself, flapping my polyurethane fins just enough to stay horizontal and giving a half-second push on the thumb-activated, rubber-capped trigger at the end of an insulated tube protruding from my buoyancy control vest. The vest inflates slightly with a gentle, echoing scrick. My breath leaves me in a burbling stream of rising, distended bubbles, a quiet bass drum rumble augmented by the brushes-scraping-across-snare click of my demand regulator’s valve. Neutral buoyancy achieved, breathing free and easy beneath four storeys of salt water, I hover an arm’s length from the reef wall in an alien repose that feels much closer to floating magically above a forest canopy than to swimming.
“It is excusable,” Charles Darwin wrote from the deck of the Beagle in 1836, “to grow enthusiastic over the infinite numbers of organic beings with which the sea of the tropics, so prodigal of life, teems.” Word to that, Charlie — and you didn’t even have the scuba gear to bring you down here to front-row seating so close to the prodigiousness you feel almost as if you’re of it.
Hold still and fix your gaze anywhere, really, and the universe is born anew in otherworldly hues and you-gotta-be-kidding-me shapes. Tiny fish the colour of a roadworker’s safety vest or the hat on a backwoods hunter’s head — don’t-hit-me yellow, don’t-shoot-me orange — dart in and out of the coral fronds. The waving tentacles of an anemone have a multihued, translucent aspect, like something you’d find protruding from the forehead of a comic book alien. A school of trevally cruises by in an orderly procession so broad and dense you think for a second the sea is actually made of fish. Look down, and there’s the mouth of a giant clam, the orifice mostly sealed by a membrane of electric purple and emerald green in intricate screensaver squiggles. Sergeant major fish will swim right up to the tempered glass of your mask and wait there expectantly like autograph seekers, giving you ample time to wonder whether you’d best describe the yellow splotches on the upper part of their bodies as ballpark mustard or canary, and to notice the way their distinctive black vertical stripes smear into a singular shade of pale neon blue at the dorsal fin and tail.
And then there’s the extraordinary symbiotic web the reef’s myriad denizens have woven, enabling this aquatic Babel to thrive more or less self-sufficiently for millennia. Hermaphrodites and sex changers abound. A great many of the reef’s coral polyps mate once a year, simultaneously, in a great cloud of eggs and sperm whose release is precisely timed with the lunar cycle. Certain species of parrotfish, their scales resembling the most ambitious palette Matisse ever dared to play with, start out female and then switch gender in four stages, each more vividly coloured than the last, eventually reaching a dazzling final act that’s been called “super-male.” Some of the zaniest colouring elsewhere, meanwhile, is “aposematic,” which is to say it’s a warning flag to would-be predators of something that tastes terrible or hurts to bite.
Damselfish tend permanent gardens of algae and chase off interlopers like rabid guard dogs; blue tang have taught themselves to successfully invade these gardens in swarms. Different species of nocturnal squirrel fish have specialized within their genus on particular kinds of food — some eating only this type of crab, others only this size of prawn. Speaking of which, there are several species of prawn and certain kinds of small fish as well, collectively referred to as “cleaners,” who live a significant chunk of their lives inside the mouths of other fish.
It’s like contemplating the cosmos under a starry sky, only the planets and constellations are close enough to touch, and they swirl past you as though you were a comet in their midst. I could float here in this reverie until my oxygen ran out — divers have — but I’m eased out of my trance by the dive leader. She’s a credentialed marine biologist, and she’s just risen from a sea-floor bed of coral below us with a rare treat in her hand. She waves her hand up and away like she’s releasing a bird, and I watch a flatworm the size and shape of a piece of Scotch tape drift slowly downward between us. The body undulates like a flag in a breeze as it descends, revealing a black sheen on one side, an explosion of deep red and purple and yellow on the other. The reef’s endless variety in microcosm, twisting and dancing between us on the current. I read somewhere that they once analyzed a single three-kilogram chunk of dead Great Barrier Reef coral and found 1,300 worms from about 100 species living in its labyrinth of orifices and folds.All due respect, Charlie, but it’s not just that the reef teems with life; it’s that it seems like the reason we coined the term. To teem is to exhibit the properties of a coral reef. I watch the flatworm descend against a writhing backdrop of coral fronds and bustling shoals of fish, and I try to imagine what it means that this little kidney-bean reef is one in a chain of 3,650 — a profusion of life stretching from a few hundred kilometres south of here all the way up the remaining length of the northeastern Australian coast and beyond, 1,800 kilometres in total. The Great Barrier Reef: the largest living system on earth, a deeply interconnected macro-organism comprising nearly a tenth of all the coral reef there is.
Coral reefs worldwide occupy only about 0.17 percent of the ocean’s surface area, but they provide habitat for nearly one-quarter of its marine life, all of it derived from a flawless, fragile symbiosis between coral polyps — the animals that form all those elaborate, plantlike structures — and a particular strain of algae called zooxanthellae. The polyps, fed by the photosynthesizing zooxanthellae that live on their bodies, grow up to secrete their own skeletons, bundles of calcium carbonate the zooxanthellae combine with ionized carbonates dissolved in the ocean’s water to cement into place as limestone, thus providing a hospitable habitat for yet more corals.
