“So many centuries after the Creation, it is unlikely that anyone could find hitherto unknown lands of any value.”
SPANISH ROYAL COMMISSION, REJECTING CHRISTOPHER COLUMBUS’S PROPOSAL TO SAIL WEST
Nowhere is the repeated lack of creativity of humans, or at the very least Western scientists, made as clear as in the history of the study of oceans. For early explorers and scientists, the ocean’s depths were populated by mermaids and ghouls. The 1823 Encyclopaedia Britannica entry for “Sea” reads, “…the sea beyond a certain depth has been found unfathomable.” We could imagine anything we liked in the deep sea. No one could check. It was unseen, unstudied, and imbued with mystery and possibility.
In 1841, Edward Forbes, a twenty-six-year-old ecologist already of some renown who would burn bright and die young, began an expedition to sample the seafloor of the Aegean. It would be among the first serious and systematic attempts to explore what was found in the deeper reaches of the sea. Forbes traveled aboard the HMS Beacon, and from that ship took dredge samples by dropping a canvas bag, controlled by ropes, to the seafloor at different depths. In 1840, the sea was still “unfathomable,” so what Forbes might find was not altogether clear. Forbes had spent his life preparing for the expedition. As a child, he collected everything from the natural world that he could. He “spent hours arranging, classifying and drawing all manner of objects, including minerals, fossils, shells, dried sea-weeds, hedge-flowers and dead butterflies.”1 By the age of twelve he had founded a natural history museum in his house.* By the time the HMS Beacon left the dock, he was ready.
As his dredges came up, he began to get his first real view of the deep ocean’s floor. The sea bottom seemed to him to present “a series of zones or regions…each peopled by its peculiar inhabitants.”2 As he sampled deeper sections of the seafloor, the inhabitants grew different, and also rarer. He could, given his equipment, sample no deeper than 230 fathoms, but at that depth there was little life. His samples came back cold, dense, and inert.
In finding few living forms in his deep samples, Forbes might have wondered how effective his sampling equipment was (not very). He might have wondered whether the Aegean was a particularly unproductive sea (it is). He might have wondered many things. Instead, he offered a new general law as to the distribution of life. He predicted that given how little he found when he sampled the seafloor at 230 fathoms, that he would find no life deeper than 300 fathoms, whether in the Aegean or anywhere else in the world.†3
That nothing lived in the depths of the sea was a simple enough prediction. It made mermaids and sea monsters unlikely, but science was perhaps ready to stop believing in them anyway. Once said aloud, the idea of the lifeless deep was intuitive, and intuitive ideas, even if wrong, ensconce themselves in science and society quickly. They hold tight because they are obvious. We believe easily that you will get a cold if you go outside when it is cold (despite overwhelming evidence to the contrary). We also believed easily that the ocean’s deep was dead. Within a generation, the ocean bottom, once filled with demons, turned in scientists’ minds into a cold, lifeless abyss. As simply as if he had waved a magic wand, Forbes had killed the deep.4
There were, of course, early doubts. Every so often, something strange would surface, dragged up in a fisherman’s net, or hauled up in a dredge, but such discoveries were largely ignored. New finds deeper than 300 fathoms seemed easiest to explain away (at least to Forbes’s disciples) as exceptions or the result of sampling that was somehow flawed. The idea that what is visible to us is all that exists is, perhaps, comforting; how else to explain how easily we accept that we know the world, that there is nothing new left to find?
Not everyone believed the deep was dead. It was, a few imagined, too big an environment to be lifeless.* Soon the skeptics began the search for deeper life, life in the biggest habitat on Earth. Few tasks are more delightful in science than disproving what is regarded as a universal truth. Charles Wyville-Thompson, a Scottish naturalist of some regard, was committed to resolving the conundrum. It did, after all, seem perfectly resolvable. There either was or was not life below 300 fathoms. He organized a series of dredging expeditions off the coast of Europe to sample life on the seafloor at different depths, first in the HMS Lightning and later in the HMS Porcupine. Life was found down to 650 fathoms. And still, not all were yet convinced.† Forbes might simply be wrong about where the azoic zone began. Wyville-Thompson wanted even deeper samples from even more places.
Wyville-Thompson staged a new expedition along with William Benjamin Carpenter from the University of London, (who had led the Lightning and Porcupine samplings) and four other scientists. The samplings they had already done had convinced them that Forbes was wrong. In fact, Wyville-Thompson soon believed that the seafloor was, at depths, “the land of promise for the naturalist, the only remaining region where there were endless novelties of extraordinary interest ready to hand.”5 Wyville-Thompson and Carpenter wanted to prove the azoic hypothesis wrong, but they were also, more simply, thrilled with the process of discovery. Each dredge held the possibility of an entirely new form of life, so of course they wanted to go much deeper.
Wyville-Thompson and Carpenter did not go meekly into their search. In the winter of 1873, a scientific ship, the HMS Challenger, with Carpenter and Wyville-Thompson aboard, left the shores of England. It was the best-fitted ship in the history of exploration for conducting biological research at sea. It was filled with special winches, enough rope to stretch from Florida to North Carolina, a crew of two hundred, and every conceivable jar, flask, and sorting bin. Go big or go home seemed to be the motto. It was still conceivable that this tremendous expedition would find very little at the bottom of the sea. As the ship pulled out, many ashore imagined the deep ocean the way we now imagine space: dark, lifeless, and, for those who venture there, lonely. The Challenger, some of Forbes’s intellectual descendants mumbled, would fail.
The Challenger returned to Spithead on May 21, 1876—three years after it had initially left the dock riding low in the water—quite literally burdened with life: 2,270 jars, 1,749 bottles, 1,860 glass tubes, and in them luminous fish, corals, crabs, worms, and many other organisms.*6 It had traveled and sampled the world. The deep was not barren. All told, the expedition yielded thousands of species, as many as 4,700 of them new to science. There were blind fish, stalk-eyed fish, glowing fish, fish with glowing slime, fish with organs of no known function, and more, much more. With the invertebrates, the crew was “embarrassed with riches,” a near infinite tumble of strange forms that sound more like Dr. Seuss characters than real species; a paper thin volute, a new Guivillea, the beautiful Pecten watsoni, and on and on.”7 Nearly each new dredge produced more new species, so much that it was obvious even by the end of the trip that the expedition did not come close to finding what could be found. If we imagine the dimensions of life, the places on Earth inhabited by life, they changed with the Challenger expedition. The deepest samples of life encountered were not from 300 fathoms, as Forbes had predicted, but from roughly 2,500 fathoms: 15,000 feet.
Wyville-Thompson, Carpenter, and colleagues had proven for good, it seemed, that life existed to great depths on the bottom of the ocean. In doing so they had found the biggest habitat known on Earth, one that just a few years earlier had been ruled out entirely. Because of the size of the sea, their work increased the size of biosphere, the living part of the Earth, dramatically.* Yet Carpenter (and others) would all too easily repeat Forbes’s mistake. At the end of his book about the expedition Carpenter would write, “there is every reason to believe that the fauna of deep water is confined principally to two belts, one at and near the surface and the other on and near the bottom; leaving an intermediate zone in which larger animals, vertebrate and invertebrate, are nearly or entirely absent.” He thought that the vast majority of the ocean, those middle layers, was still dead. He had not rid marine biology of the azoic zone, he just moved it.
Carpenter, in addition to suggesting that the middle of the ocean was azoic, would make other general predictions. Among them was an explanation for how the life he and the other scientists aboard the Challenger found at the bottom of the sea, where there is no light for photosynthesis, lived. Carpenter argued that the life at the bottom lived by consuming dead things that fell from the lighted layers above (oceanographers call this fall of bodies marine snow).* The species that he had found in his dredges were the beasts that cleaned up the mess, the oceans’ undertakers, grim, colorless, and bizarre. Life at the depths might be more diverse than Forbes had thought, but it was, with absolute certainty, a richness suspended on the fruits of the sun. Like the azoic hypothesis, this idea too would prove both intuitive and wrong.
Long after the Challenger expedition, the idea that there was little life at the bottom of the ocean remained. No one said the layer was azoic, but it was often thought of as a kind of desert, a biologically spare and harsh environment—not lifeless, but not bountiful either. In the 1960s, nearly a hundred years after the Challenger returned to dock, a series of papers concluded, in rapid succession, that there were far more species at the bottom of the ocean, below 12,000 feet (2,000 fathoms), than had been expected. Yet these papers were not, at least immediately, well read. When geologists began to use submersibles to explore the ocean floor, they, again, expected a desert. They expected that the big discoveries in the deep sea, if there were any, would be geological.
In the 1960s and early 1970s, plate tectonics was finally gaining credibility and, with that nascent credibility, clearer predictions about what the bottom of the sea should be like. The bottom of the sea was an important place for understanding the movement of the continents. Plate tectonics was controversial and in that controversy was excitement. Some scientists still doubted plate tectonics occurred (textbooks still largely recorded it as one of several theories), and one of the doubts had to do with somewhat obscure predictions about the temperature of water at the bottom of the sea. As early as 1965, models predicted that there should be deep-sea springs or vents near the rifts where the continents were dividing. None had yet been found. A great deal hinged on their discovery, or lack thereof.
Such were the circumstances and expectations when, in February 1977, an expedition was launched to a site 340 kilometers north of the Galapagos, not far (at least horizontally) from where Darwin studied finches. The expedition team had come together at the Panama Canal to ready for the trip. The team included geologists and geophysicists, but (conspicuously) not biologists.* They boarded the two expedition ships, Knorr and Lulu, and began to ready themselves for what was ahead. On board with them were the Alvin submersible and an unmanned device, ANGUS, which could be towed over the seafloor to take pictures. Both would be put to full use. Forbes dropped cloth bags down to 250 fathoms. This team would descend, inside a submersible, to depths of more than a mile (880 fathoms).
The scientists’ mission was to explore the bottom of the ocean for deep-sea vents at the rifts where the seafloor was spreading. They wanted badly to find the hot-water vents that theory had predicted and anecdotal observations had suggested might be present. It was a very expensive mission and a great deal was on the line. There were good omens. During an expedition in 1976 using an unmanned submersible, other scientists had already detected anomalous heat in the area and had made observations of “ventlike forms.”† Yet what would be found was still uncertain. The ocean floor was enormous and nearly every inch of it was unexplored. At the moment the expedition began, even the surface of the moon was better known.
The team began by searching for hot spots that might indicate areas where there were vents. To find the hot spots, the team pulled the unmanned vehicle, ANGUS, also known as “dope on a rope,” behind the surface vessel, Knorr, at a depth of 9,000 feet (1,500 fathoms). Beginning on the morning of February 15, the Knorr motored around and the scientists waited for the ANGUS to find a warm spot. If there were no vents, the waiting might have lasted the entire expedition. But at about midnight they found a warm area. Eureka? They continued to drive back and forth until the ANGUS, which carried a camera, ran out of film and then brought it back up to look at the film, to see what, in that moment of warmer water, the ANGUS had seen. As they developed the pictures, they saw something very strange: clamshells. The clamshells made little sense. Perhaps they had fallen from above? Had anybody on board been eating clams?
Two scientists, Tjeery (“Jerry”) van Andel and Jack Corliss, got into the Alvin submersible with the pilot, Jack Donnelly, and headed down toward the site that would later be called Clambake. Everyone was excited about what they might find. Within half an hour, van Andel and Corliss found vents. The vents shimmered in their own warmth and were more amazing than anticipated.* Currents move water down through the sediment and rock layers and into the ocean floor, where it is superheated and then rises back up, through the rock and out of the deep sea vents, which grow through the deposition of heated minerals. It was one of the most significant geological discoveries in many years—some would say decades. In moments of hyperbole, a few of those involved would say, “the most significant in centuries.” But the vents themselves would not be the biggest discovery.
The biggest discovery would come a moment later, when the crew in the Alvin found the clams that had been spotted on the photos from ANGUS. The clams were enormous and very much alive. Corliss announced into the radio that it looked like they were at a clambake. And then he radioed up again, “Isn’t the deep ocean supposed to be like a desert?…Well, there’s all these animals down here.” And it wasn’t just the clams.
Through the Alvin’s portholes the three men saw two-foot-long clams, crabs, and more. On later dives they would see tubeworms, colored ridiculously in oranges and reds. But already on the first dive, life was bountiful where it was thought to be absent. As Jerry van Andel looked out his porthole, he saw a fish—a “big round rosy face, maybe two hands across, that came right” to his porthole. They “couldn’t get rid of him. [They] would turn Alvin and move again and yet he was always there” at the porthole, a beacon of life. Life had been discovered, that much was soon clear (though each scientist would need to see it for themselves before they really “understood”), but something seemed very unresolved. Though there was life around the vents, more life per inch of habitat, it would later turn out, than nearly anyplace on Earth, it was totally unclear why it was there. We have, for centuries, thought about the world as an “animals eat plants” kind of place, but these vents seemed so far removed from both the green of trees and the more proximate plankton. Even the sea snow that falls everywhere in the oceans barely reaches the depths at which the vents were found. The first thought was that the vents were just warmer than the surrounding sea and that the life, still dependent on falling matter for food, gathered around the warmth.8
The big story, a kind of revelation, would emerge slowly in part because no biologists had come on the 1977 mission. Nor was there much equipment on the Alvin intended for collecting biological samples, so confident was the team of the lifelessness of the realm they were exploring. Van Andel would later say that he and the cook, who had a biology degree, were the only ones who were initially interested in the life that had been found on the vents. Van Andel, after he saw the life on the vents, “did not give a damn about the hot springs themselves at that point.” He knew the life was the bigger discovery. Later others would be convinced, but depending on whose report you believe, not initially. The team had limited dive time and many things to explore and because they were geologists and geochemists, they did what seemed natural—they studied the springs, soon to be called deep-sea vents, and they did so with fervor.
When the dives were concluded, just a few samples of the life on the vents, nearly all of them representing species new to science, had been collected. All that came back to shore were a few vials full of seawater from near the vents, a “vestimentiferan, some clams and a galatheid crab,”9 and, collected somehow, somewhere, a few vials full of seawater from near the vents.* When biologists on shore had found out about the discovery, they radioed for the Knorr to come back immediately to pick them up, but it didn’t. There would be more time for collecting on a subsequent expedition that would soon be organized for a return, in two years. For now, it was the geologists turn to, with the clumsy appendages of the Alvin, explore the new realm of life.
More and more expeditions would follow. Since the first sighting of life on the deep-sea vents, a new species has been named from the vents about every two weeks. Like all new realms, once the vents were found, there would be much to document and explore. The mystery though, the immediate mystery, was how life survived on the vents at all. Such densities of life could not live on the slow snow of dead things alone—there just wasn’t enough. What else could be going on was not immediately apparent, but when a vial of water from the vents was opened in the lab on the Knorr, everyone started gagging and raced to open the windows. The sample smelled like hydrogen sulfide. It was a clue.
The adventure of finding the vents was only part of the discovery. The mystery of how the vent communities lived remained. Adventurers had found a lost pyramid of life, and now it was up to biologists in their labs to find the builders, the workers who had toiled to raise these cities in the deep. If it was surprising that life existed on the vents, it was surprising in large part because the conditions were thought to be both too harsh for life—too cold, too hot, too high in pressure, or too depleted in resources. Forbes was, in predicting the deep to be dead, clearly wrong. Now scientists needed to figure out why. That work would depend to a great extent on two microbiologists from the Woods Hole Oceanographic Institution, Carl Wirsen and Holger Jannasch, who would quietly begin to shape our understanding of the deep and strange world at the bottom of the sea. Over the years, Jannasch and Wirsen would work together on many projects. They shared the vision that microbial life was far more widespread, interesting, and complex than was usually appreciated. They were, at the moment that the Alvin returned with samples, as in many other important moments in their science to follow, ready for what they would find.
The geologists on board the Alvin’s mother ship tried to guess at what the life on the deep-sea vents might feed on, despite their near total lack of background in biology. That there was no life apparent even a few meters away from the vents seemed an indication that whatever the life-giving stuff was, it had to come from the vents. Some began to speculate that perhaps it had to do with sulfur, though others persisted with the idea that it was the warmth itself that was favoring life. Jannasch, along with Jon Tuttle, had just shown that microbes could grow in serum bottles containing sulfur (thiosulfate) placed on a permanent seafloor mooring.10 Their results suggested there were sulfur-dependent microbes in the deep ocean, but left open questions about their abundance and relationship to deep-sea vents.* For Jannasch and Wirsen, the deep-sea vents seemed almost immediately to be a realization of what they imagined might be possible—an ecosystem in which the primary producers harnessed energy from the Earth’s chemicals instead of the sun. In March of 1977, before the Knorr even came back to port, Jannasch suggested in an interview that what the Alvin scientists had found was a realm of life dependent on hydrogen sulfide.11 If he were right, all of our everyday assumptions about where life could live, on Earth and beyond, might be wrong.
To test their ideas, Jannasch and Wirsen would need samples from the vents. It would take more convincing data before other biologists believed that the vent communities thrived independently of photosynthesis.12 Because the initial expedition had not been prepared to find life, there had been only very modest samples of microbial community, but all those samples had shown some evidence of sulfur bacteria. A new expedition was organized for January 1979, and this time they brought more vials—thousands more.
Using samples from the 1979 expedition, Jannasch and Wirsen made observations of the microbial activity in and around the vents. They would, through a great deal more work, find support for their initial intuition. The life at the vent was thriving not on derivatives of the sun, but on the chemicals released from the vents. Those chemicals included hydrogen sulfide, but, as time and more research would tell, also a variety of other chemicals. Here then was the first example of an ecological realm based almost entirely on energy from the Earth itself.* Microbes ate the chemicals and everything else, in all sorts of complex ways, depended on them. It was a world nearly independent of the sun. Were the sun to die out, this world at the bottom of the sea might just survive, at least for a while.* It may have already survived hundreds of millions or even billions of years. In fact, these deep-sea vents may be more like what most of the history of life on Earth has been than are our present photosynthetic realms. Before photosynthesis evolved, all living realms used chemical energy, the Earth’s energy. Here, in the vents, was a kind of window into the past. It would soon even be suggested that perhaps life had first evolved on the deep-sea vents. The deep ocean had turned, in a few years, from moonlike to motherly.
Just as the first mystery of the productivity of the deep-sea vents was resolved a new mystery would emerge. Tube worms (various species of the genus Riftia) are the most abundant animal on most of the vents. Yet when the tube worms were studied closely, it was discovered that they had no mouth, anus, or digestive tract. One could be forgiven for believing that the entire story of the vent communities was made up. Nothing having to do with the vents seemed ordinary. The worms, a then graduate student, Colleen Cavanaugh, would reveal, possessed an organ called the trophosome, which housed microbes. By living in the trophosome, the microbes have a fertile place to reproduce. In exchange, the microbes provide the tube worms with organic carbon (which results when the microbes use the energy from hydrogen sulfide to turn carbon dioxide into usable carbon). Here then at the heart of the deep-sea vent communities was a symbiosis, a symbiosis that may have in part allowed the colonization of the vents by animals in the first place, but that also made the vents more favorable for microbes, which seem much denser in the presence of the worms than they would be otherwise.
The tube worms are not unlike trees, except that their sun is the Earth and its chemicals. The chloroplasts are replaced by the microbes that use hydrogen sulfide for energy. The tube worms use their long gills like leaves to harness the energy around them. The gills are red with the special hemoglobin that transports both hydrogen sulfide and oxygen (the hydrogen sulfide fuels the microbes and both the microbes and the worm need the oxygen). The tube worm’s realm is, in its particulars, like an alternate universe of life. One is tempted to wonder what would happen if tube worms, with their microbes, had become the predominant primary producer on Earth instead of trees. One is then reminded that in either case it is the microbes that are really harnessing the energy, all of it, whether in the trophosome or in their more derived condition, as chloroplasts in cells. Most of the primary productivity at the vents, perhaps as much as ninety percent, now appears to occur in the symbiotic microbes and the animals in which they live. The giant clams and some of the other animals on the vents have also been shown to play host to microbes.* If Lynn Margulis had dreamed up a world, this might be it—a place where everything depended on symbiosis, a place where the wild tube worms waved their red gills as if to flaunt that, where nothing was imagined, life thrives.
The deep-sea vents held life, where there should have been none, but as scientists continued to study the vents there appeared a new habitat where life seemed, again, unlikely. The hot deep-sea vents, the black smokers, can reach temperatures of up to 380°C, temperatures high enough to melt submarines and surely all life. The hottest temperature fish can live at is 38°C. The highest temperature plants can live at is 45°C. Pasteurization, after all, relies on the generality that all life is killed at 80°C. But the communities around deep-sea vents held more secrets. When the vents were sampled, life was found, not at the very hottest temperatures, but at far higher temperatures than had been suspected. The microbes living in the heat of the vents are among the most heat tolerant life on Earth. They could live at temperatures up to 121°C. They seemed, in their tolerance, to foretell even more discoveries. If life could tolerate such temperatures, what else could it tolerate? Many of these tolerant life-forms were archaea. The obscure branch of life Carl Woese had discovered seemed, more and more, to live everywhere that life could be. It has been said that in discovering the archaea Woese “lifted a whole submerged continent out of the ocean,” but it was at the bottom of the ocean where Carl Woese and Lynn Margulis’s worlds found their ideas’ culmination in the deep gardens of the sea.13
The hypothermophile archaea that were discovered in the deep sea would play a prominent, if brief, role in Woese’s life—a role that would seem to accentuate the complexity of his story. The guru of genetic sequencing (including, for example, the sequencing of the human genome), Craig Venter, began a project with Woese to sequence the genome (decode every letter in its DNA) of a single species of deep-sea archaea, Methanocaldococcus jannaschii, named for Holger Jannasch.* For Woese the project was wonderful news. He hoped it would show just how different the archaea are from bacteria and eukaryotes. Here would be the grand confirmation of Woese’s years of work, a confirmation that was no longer necessary but for which he would still be glad.
When the entire genome was sequenced, the archaea species, M. jannaschii, was indeed very, very different from any bacterial species ever sequenced. It was more different even than Woese had expected. On the big day, the day of the media announcement, a day that must have recalled the day when the New York Times article first appeared, one might have hoped for some final vindication for Woese. Instead, Venter stole the show. Woese’s long-distance TV connection did not work well. Venter told Woese to try not to talk too much. The day was Venter’s. Venter claimed to have “shown for the first time that the archaea were really very different.” The New York Times article mentioned Woese this time only briefly, as a collaborator. Meanwhile, the discoveries that would come from the small life-forms on the bottom of the sea were not yet done.