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
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
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.”
No chance of that happening with all of Kingman’s resident sharks. Parrotfish, whose beak-like incisors evolved to gnaw the most tenacious coral-choking algae, even change sex to maintain their sizzling reproduction rates. The healthy reef keeps its system in balance by providing nooks and crevices in which small fish hide long enough to breed before becoming shark food. As a result of the constant conversion of plant and algae nutrients into short-lived little fish, the long-lived apex predators end up accumulating most of the biomass.
The expedition data would later show that fully 85 percent of the live weight at Kingman Reef was accounted for by sharks, snappers, and other carnivorous company. How many PCBs may have migrated up the food chain and now saturate their tissues is fodder for a future study.
Two days before the expedition’s scientists depart Kingman, they steer their dive boats to the twin crescent islets heaped atop the northern arm of the boomerang-shaped reef. In the shallows, they find a heartening sight: a spectacular community of spiny black, red, and green sea urchins, robust grazers of algae. A 1998 El Nino temperature fluctuation, ratcheted even higher by global warming, knocked out 90 percent of the sea urchins in the Caribbean. Unusually warm water shocked coral polyps into spitting out friendly algal photosynthesizers that live in tight symbiosis with them, trading just the right balance of sugars for ammonia fertilizer the corals excrete back, and also providing their color. Within a month, more than half the Caribbean reefs had turned to bleached coral skeletons, now coated with slime.
Like corals worldwide, the ones at the Kingman islets’ edges also show bleaching scars, but fierce grazing has kept invasive algae at bay, allowing encrusting pink corallines to slowly cement the wounded reef back together. Wading gingerly around all the sea urchin spikes, the researchers climb ashore. Within a few yards, they’re on the windward side of the clamshell rubble, where they get a shock.
From one end to the other, each isle is carpeted with crushed plastic bottles, parts of polystyrene floats, nylon shipping ties, Bic lighters, flip-flops in various states of ultraviolet disintegration, plastic bottle caps of assorted sizes, squeeze-tubes of Japanese hand lotion, and a galaxy of multicolored plastic fragments shattered beyond identity.
The only organic detritus is the skeleton of a red-footed booby, chunks of an old wooden outrigger, and six coconuts. The following day, the scientists return after their final dive and fill dozens of garbage bags. They are under no illusions that they have returned Kingman Reef to the pristine state it was in before humans ever found it. Asian currents will bring more plastic; rising temperatures will bleach more corals—possibly all of them, unless coral and its photosynthetic resident algal partner can evolve new symbiotic agreements quickly.
Even the sharks, they now realize, are evidence of human intervention. Only one that they’ve seen in Kingman all week was a behemoth longer than six feet; the rest are apparently adolescents. Within the past two decades, shark finners must have been here. In Hong Kong, shark fin soup commands up to $100 per bowl. After slicing off their pectoral and dorsal fins, finners throw mutilated sharks, still alive, back into the sea. Rudderless, they sink to the bottom and suffocate. Despite campaigns to ban the delicacy, in less remote waters an estimated 100 million sharks die this way every year. The presence of so many vigorous young ones, at least, gives hope that enough sharks here escaped the blade to revive the population. PCBs or not, they look to be prospering.
“In a year,” observes Enric Sala, watching their spotlit frenzy that night from the rail of the
Enric Sala stands on the shore of Palmyra Atoll, waiting for a turbo-prop Gulfstream to land on the airstrip built here the last time the world was officially at war, to take his expedition team back to Honolulu—a threehour flight. From there, they’ll disperse across the globe with their data. When they meet again, it will be electronically, and then in peer-reviewed papers they will coauthor.
Palmyra’s soft green lagoon is pure and lucid, its tropical splendor patiently erasing crumbled concrete slabs where thousands of sooty terns now roost. The tallest structure here, a former radar antenna, has rusted in half; within a few more years, it will disappear completely among the coconut palms and almond trees. If all human activity suddenly collapsed along with it, Sala believes that quicker than we’d expect, the reefs of the northern Line Islands could be as complex as they were in the last few thousand years before they were found by men bearing nets and fishhooks. (And rats: probably the onboard, self-reproducing food supply for Polynesian mariners who dared cross this endless ocean with only canoes and courage.)
“Even with global warming, I think reefs would recover within two centuries. It would be patchy. In some places, lots of large predators. Others would be coated with algae. But in time, sea urchins would return. And the fish. And then the corals.”
His thick dark eyebrows arch beyond the horizon to picture it. “In 500 years, if a human came back, he’d be
