The current Alvin has been repaired and refitted so many times that the original parts are gone, but the design and model remain, as does the little sub’s growing list of accomplishments. None, however, can surpass the raw excitement generated by the findings made on the first dive to the Galápagos Rift, some 200 miles (320 km) northeast of the Galápagos Islands, in August 1977.

American geologist Jack Corliss (then at Oregon State University, now at Central European University, Budapest) and John Edmond, a Scots geochemist based at the Massachusetts Institute of Technology, were on that first dive. As they were cruising along the rift, about 1½ miles (2.4 km) down, their eyes wide open, the pilot suddenly noticed a white crab on the seafloor. As they had seen almost no life in an area that Corliss described as smooth and glassy, it was a surprising sight. Shortly thereafter, the water began to turn milky and cloudy, and Corliss noticed that his specially adapted underwater thermometer began to indicate a steady rise in temperature. The alarm on the device went off, signaling an even higher temperature. And then the pilot announced excitedly, “There are clams out here!” 

As Alvin drew nearer, Corliss and Edmond were treated to their first glimpse of the “Rose Garden,” a strange oasis in this submarine desert, as they later described it. They had found the hot springs, the hydrothermal vents, and there was life everywhere: clams, mussels, tubeworms and more. And these were not just any clams but ghostly white, giant foot-long (30 cm) clams, as well as six-inch (15 cm) mussels. Waving in the currents all around them were densely packed snakelike tubeworms up to 3½ feet (1 m) long. They were attached deep within the crevices and sported red flower-bud-like tips. The lights from Alvin illuminated and uncovered this overgrown deep-sea garden in all its wonder.

Corliss and Edmond’s first thought on seeing the bizarre, monstrous-sized creatures was that they had stumbled upon a primordial ecosystem far removed from time and certainly never before seen by humans. Perhaps it dated back millions of years to some lost world. As the news hit the scientific community through Nature, Science, New Scientist and The New York Times, the buzz echoed the excitement generated up to a hundred years earlier by the deep-ocean, living-fossil search. But these were not fossils, living or otherwise. The tubeworms and most of the other dominant animals were probably recent in origin—less than 100 million years old. They were young and alive. It proved that there are amazing secrets of the Earth’s biological and geological history to be found in distinct corners, ridges and trenches of the world ocean. The process of revealing them would cast vital light on marine biology, microbiology and various subdisciplines of earth science. The textbooks would have to be rewritten.

Life at the hydrothermal vents appeared to bend all the previous rules. The animals here were not slow-growing, as were most of the deep-sea fauna, but fast-growing, fueled by some extraordinary energy source. While Corliss and Edmond sensed this, they had no idea how these animals could thrive. At 50 to 68 degrees F (10–20°C), the water was warm compared with the 36- to 39-degree-F (2–4°C) temperature of most of the deep sea. And amazingly, the water was loaded with toxic hydrogen sulfide. Alvin gathered a few samples of the tubeworms and mollusks for biologists onshore, and the basic story soon emerged. What Corliss and Edmond had found was the first ecosystem on Earth that didn’t get its energy from the sun, from photosynthesis. The basis of the food web was not photosynthetic organisms. But what was it?

When biologists began to dissect the giant tubeworms—creatures with no mouths or digestive systems—they experienced an overpowering stench. More than one researcher found that the foul odor could clear the lab of all those uninitiated to the deep, allowing for hours of undisturbed study. In fact, the tubeworms were full of bacteria that they were, in effect, feeding on. The clams and mussels had bacteria in their tissues too. Other animals at the vent also appeared to be living with, or possibly on, bacteria, filtering the microorganisms from the water or grazing on the bacterial film on the rocks.

In the early 1980s, graduate student Colleen Cavanaugh, now a professor of biology at Harvard University, first proposed that the giant tubeworms obtain their food from bacteria living within their cells. Through a process called chemosynthesis, the bacteria transform methane and sulfur, among other inedibles, into organic molecules upon which the tubeworms feed. Around the same time, Holger W. Jannasch of the Woods Hole Oceanographic Institution and David Karl of the University of Hawaii at Manoa were looking at vent bacteria. They were able to show experimentally that these bacteria depend on hydrogen sulfide and other forms of sulfur, thus revealing the vital link between the bacteria and the sulfur at the vents. Scientists began to realize that these bacteria support an entire hydrothermal ecosystem. Instead of photosynthetic phytoplankton, these so-called chemosynthetic bacteria proved to be the organic basis of the food web in the hydrothermal-vent community. 

The hydrothermal vents stand as one of the great discoveries of the late 20th century. The early reports trumpeted bacteria living at 480 degrees F (250°C), tubeworms belonging not only to new species but to new phyla and the dependence of the ecosystem on chemosynthesis. In fact, the maximum known temperature habitat for a microorganism is about 240 degrees F (115°C), with theoretical limits of up to 300 degrees F (150°C), but the hottest vent temperature has recently been measured at 765 degrees F (407°C). The giant tubeworms, bizarre and unclassifiable as they first seemed, have proved to be a kind of annelid worm. To date, despite early indications of possible new phyla, none have been confirmed from the vents. Finally, the dependence on chemosynthesis is more complicated than first envisioned.

Vent animals also need the sun and photosynthesis. The various tubeworms, clams, mussels and other vent animals are aerobic; that is, they need oxygen, as do all large multicellular organisms. The oxygen they obtain from seawater comes from photosynthesis. Further, even though the organic basis of the food web is chemosynthesis, or chemosynthetic bacteria, the chemical energy used by the bacteria comes from oxidation of sulfide. Still, strange species were found at the hydrothermal vents, living in a new type of ecosystem.

At first, the discovery of the unlikely hydrothermal-vent ecosystem was thought to be a rare occurrence. Were there more vents out there with the same or different animals? In the wake of Alvin’s 1977 success, new expeditions set out to search all along the volcanic midocean ridge where tectonic plates met, first in the North Pacific and then in the North Atlantic and Indian oceans. Alvin was in demand now more than ever before. Scientists and technicians scrambled for ship and submarine time, and many were prepared to spend Christmas and other holidays at sea. As hard as it was for a biologist to be away from friends and loved ones at such times, being on Alvin or the supporting ship, gathering samples of strange new worms, mussels and shrimp, not to mention bacterial microbes, was a fair substitute for traditional celebrations.

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