Arthur Clarke - Imperial Earth

Now that he had mastered the use of the snorkel tube, he kept his head under water all the time, and even essayed shallow dives which involved holding his breath for considerable periods. The panorama beneath was so fascinating that Duncan even occasionally forgot the need for air, and emerged sputtering foolishly.

The first signboard was at a depth of five meters and said, in fluorescent yellow letters: NO UNAUTHORIZED VISITORS BEYOND THIS POINT. The second warning was a flashing holographic display in midwater, which must have been very perplexing to the fish. It announced ominously: THIS REEF IS MONITORED. Duncan could see no trace of the projectors; they had been very cunningly concealed.

Todd was pointing ahead, to the line of divers working along the edge of the reef. So he had not been joking. They really were going through the unmistakable motions of gardeners digging up noxious weeds. And each one was surrounded by a small cloud of brilliantly colored fish, clearly benefitting from all this activity.

The coral formations seemed to be changing shape. Even to Duncan’s untrained eye, they looked strange—even abnormal. He had grown accustomed to the branching antlers of the staghorns, the convoluted labyrinths that looked like giant brains, the delicate mushrooms sometimes meters in diameter. They were still here, but now subtly distorted.

Then he saw the first metallic glint—then another, and another. As he came closer, and the blue haze of distance no longer softened the details of the underwater world, Duncan realized why this reef was cherished and protected.

Everywhere he looked, it glittered and sparkled with gold.

Two hundred years earlier, it had been one of the greatest triumphs of biological engineering, bringing world fame to its creators. Ironically, success had come when it was no longer required; what had been intended to fulfill a vital need had turned out to be no more than a technological cul-de-sac.

It had been known for centuries that some marine organisms were able to extract, for the benefit of their own internal economies, elements present in seawater in unbelievably small proportions. If sponges and oysters and similar lowly creatures could perform such feats of chemical engineering with iodine or vanadium, the biologists of the 2100’s had argued, why could they not be taught to do the same trick with more valuable elements?

And so, by heroic feats of gene-manipulation, several species of coral had been persuaded to become gold miners. The most successful were able to replace almost ten percent of their limestone skeletons with the precious metal. That success, however, was measured only in human terms. Since gold normally plays no part in biochemical reactions, the consequences to the corals were disastrous; the auriferous reefs were never healthy, and had to be carefully protected from predators and disease.

Only a few hundred tons of gold were extracted by this technique before large-scale transmutation made it uneconomic; the nuclear furnaces could manufacture gold as cheaply as any other metal. For a while, the more accessible reefs were maintained as tourist attractions, but souvenir hunters soon demolished them. Now only one was left, and Dr. Mohammed’s staff was determined to preserve it.

So, at regular intervals, the doctors and nurses took time off from their usual duties, and enjoyed an arduous working holiday on the reef. They dumped carefully selected fertilizers and antibiotics to improve the health of the living corals, and waged war against its enemies—particularly the spectacular crown of thorns starfish and its similar relative the spiny sea urchin. Duncan floated, perfectly relaxed, in the tepid water, lazily flippering from time to time so that he remained in the shadow of the dinghy. Now he understood the purpose of those sinister knives and spikes; the adversaries they had to deal with were well protected indeed.

Only a couple of meters beneath him, one of the divers was jabbing at a colony of small black spheres, each at the center of a formidable array of needle-sharp spines. From time to time one of the spheres would be split open, and fish would dart in to grab the pieces of white meat that came floating out. It was a delicacy they could scarcely ever have enjoyed without human intervention; Duncan could not imagine that these spiky beasts had any natural enemies.

The diver—one of the nurses—noticed the two spectators hovering overhead, and beckoned Duncan to join her. He had become so fascinated that he now obeyed automatically, without a second’s thought. Taking several deep breaths, and partly exhaling on the last one, he hauled himself slowly down the line anchoring the dinghy to its small grapnel.

The distance was greater than he had imagined—more like three meters than two, for he had forgotten the refractive effect of the water. Midway, his left ear gave a disconcerting ‘click,’ but Dr. Todd had warned him about this, and he did not check his descent. When he reached the anchor, and grabbed its shank, he felt a tremendous sense of achievement. He was a deep-sea diver—he had plumbed the fabulous depth of three meters! Well, at least two point five...

The glitter of gold was all around him. There was never more than a tiny speck, smaller than a grain of sand, at any one spot—but it was everywhere; the entire reef was impregnated with it. Duncan felt that he was floating beside the chef-d’oeuvre of some mad jeweler, determined to create a baroque masterpiece regardless of expense. Yet these pinnacles and plates and twisted spires were the work of mindless polyps, not—except indirectly—the products of human intelligence.

Reluctantly, he shot up to the surface for air. This was easy; he felt ashamed of his previous fears. Now he understood how visitors often reacted to Titan. Next time, when someone politely declined an invitation to take a pleasant jaunt outside, he would be a little more tolerant.

“What are those black things?” he asked Dr. Todd, who was still hovering watchfully above him.

“Long-spined sea urchin, Diadema something-or-other. When you see so many, it’s a sign of pollution or an unbalanced ecology. They don’t really damage the reef—unlike Acanthaster —but they’re ugly, and a nuisance. If you back into one, the needles may take a month to work their way out. Are you going down again?”

“Yes.”

“Good. Don’t overdo it. And watch out for those spines!”

Duncan hauled himself down the anchor line once more, and the diver waved him a greeting as he approached. Then she offered him her deadly-looking knife, and pointed toward a small group of sea urchins. Duncan nodded, took the tapering metal blade by the proffered handle, and started jabbing away inexpertly, being careful to avoid those ominous black needles.

Not until then did he realize, to his considerable surprise, that these lowly animals were aware of his presence, and were not relying merely on a static defense. The long spines were swinging toward him, orienting themselves in the direction of maximum danger. Presumably it was only a simple automatic reflex, but it made him pause for a moment. There was more here than met the eye—perhaps the first faint intimations of dawning consciousness.

His knife was no longer than the sea urchin’s spines, and he jabbed vigorously again and again. The carapace was surprisingly tough, but presently it gave way, and the waiting fish raced in to grab at the creamy white flesh that was suddenly exposed.

And then, with growing discomfort, Duncan realized that his victim was not dying in silence. For some time he had been aware of faint sounds in the water around him—the hammering of the other divers on the reef, the occasional ‘clang’ of the anchor against the rocks. But his noise came from much closer at hand, and was most peculiar—even disturbing. It was a crackling, grinding sound; though the analogy was patently ridiculous, it could only be compared to the crunching of thousands of tiny teeth, clashing in rage and agony. Moreover, there was no doubt that it came from the eviscerated sea urchin.