The World Without Us

Vibrant as it is, Kingman Reef is still the aquatic equivalent of an oasis in mid-desert, thousands of miles from any significant landmass for trading and replenishing seed. The 300–400 fish species here are fewer than half of what’s on display in the great Pacific coral reef diversity triangle of Indonesia, New Guinea, and the Solomon Islands. Yet the pressure of aquarium-trade capture and overfishing by dynamite and cyanide have stressed those places nearly to breaking, and left them bereft of large predators.

“There’s no place left in the ocean like the Serengeti that puts it all together,” observes Jeremy Jackson.

Yet Kingman Reef, like the Bialowieza Puszcza, is a time machine, an intact fragment of what used to surround every green dot in this big blue ocean. Here, the coral team finds a half-dozen unknown species. The invertebrate crew brings back strange mollusks. The microbe team discovers hundreds of new bacteria and viruses, largely because no one has ever before tried to chart the microscopic universe of a coral reef.

In a sweltering cargo hold below decks, microbiologist Forest Rohwer has mini-cloned the lab he runs at San Diego State. Using an oxygen probe just one micron across that’s hooked to a microsensor and a laptop, his team has demonstrated exactly how algae that they collected earlier at Palmyra are supplanting living corals. In small glass cubes they built and filled with seawater, they placed bits of coral and seaweed algae separated by a glass membrane so fine that not even viruses can pass through it. Sugars produced by the algae can, however, because they dissolve. When bacteria living on coral feed on this rich extra nutrient, they consume all the available oxygen, and the coral dies.

To verify this finding, the microbiology team dosed some cubes with ampicillin to kill the hyperventilating bacteria, and those corals remained healthy. “In every case,” says Rohwer, climbing out of the hold into the considerably cooler afternoon, “stuff dissolving out of the algae kills the coral.”

So where is all the weedy algae coming from? “Normally,” he explains, lifting his nearly waist-length black hair to catch a breeze on the back of his neck, “coral and algae are in happy equilibrium, with fish grazing on the algae and cropping it. But if water quality around a reef goes down, or if you remove grazing fish from the system, algae get the upper hand.”

In a healthy ocean such as at Kingman Reef, there are a million bacteria per milliliter, doing the world’s work by controlling the movements of nutrients and carbon through the planet’s digestive system. Around the populated Line Islands, however, some samples show 15 times as much bacteria. Taking up oxygen, they choke coral, gaining ground for yet more algae to feed yet more microbial bacteria. It’s the slimy cycle that Jeremy Jackson fears, and Forest Rohwer agrees that it could well happen.

“Microbes don’t really much care whether we—or anything else—are here or not. We’re just a semi-interesting niche for them. In fact, there’s been just a very brief period of time when there were anything but microbes on the planet. For billions of years, that’s all there was. And when the sun starts to expand, we’ll go, and it’ll only be microbes, for millions or billions of years more.”

They will remain, he says, until the sun dries up the last water on Earth, because microbes need it to thrive and reproduce. “Although they can be stored by freeze-drying, and do just fine. Everything we shoot into space has microbes on it, despite people’s efforts to not let that happen. Once it’s out there, there’s no reason why some of this stuff couldn’t make it billions of years.”

The one thing microbes could never have done was take over the land the way more complex cell structures finally did, building plants and trees that invited more complex life-forms to dwell in them. The only structures microbes create are mats of slime, a regression toward the first life-forms on Earth. To these scientists’ palpable relief, here at Kingman that hasn’t happened yet. Pods of bottlenose dolphins accompany the dive boats to and from the White Holly, leaping to snag plentiful flying fish. Each underwater transect reveals more richness, ranging from gobies, a fish less than a’ centimeter long, to manta rays the size of Piper Cubs, and hundreds of sharks, snappers, and big jacks.

The reefs themselves, blessedly clean, are lush with table corals, plate corals, lobe corals, brain corals, and flower corals. At times, the walls of coral nearly disappear behind colored clouds of smaller grazing fish. The paradox that this expedition has confirmed is that their sheer abundance is caused by the hordes of hungry predators that devour them. Under such predation pressure, small herbivores reproduce even faster.

“It’s like when you mow your lawn,” explains Alan Friedlander. “The more you crop it, the more quickly grass grows. If you let it go awhile, the growth rate levels off.”