Once it seemed that the ocean floor was a desert of darkness. As everyone knew, sunlight was what made life possible by fueling photosynthesis, and sunlight can penetrate only the first few hundred yards of the ocean’s great depths. Lower, a few creatures might still eke out a living by scrounging the organic detritus that drifts down from the surface of the sea. But thousands of feet down, in the utter blackness at the ocean’s bottom, there could be practically nothing.
Then, in 1977, underwater explorers discovered that there was in fact something, and quite a lot of it. At midocean ridges, where new ocean floor rises up as molten rock from Earth’s interior, where cold seawater mixes with the rising magma and, heated to 650 degrees, spews back up through chimney-shaped hydrothermal vents, researchers stumbled across bustling ecosystems. Clinging to the sides of the chimneys were thick white mats of bacteria; around them were eight-foot-long stalk-shaped worms, rocking in the water, while eyeless shrimp seethed around the chimneys like maggots. All were thriving on the energy bound up in the vents’ sulfur compounds. The seafloor might still be dark, but now it was known to be dotted with gardens.
In just the past eight years, however, underwater explorers have discovered that this picture is still incomplete: there is light at the bottom of the sea. Hydrothermal vents glow, and while the light is too faint to be perceived by the human eye, that hardly means it is without significance. Physicists maintain that although some of the light may be created by the intense heat, much of it must be attributed to some as-yet- unknown process. Biologists, meanwhile, say there is sufficient light at these vents for photosynthesis to take place. Researchers can’t say yet whether any creatures are actually living off this light, but if they are, they will represent the first known instance of natural photosynthesis without sunlight. The evolutionary implications may run deeper: it’s possible not only that this deep light is fueling photosynthesis now, but that, 3.8 billion years ago, it got the whole process started.
Behind the exploration of this phenomenon, and much of the speculation surrounding it, is a woman named Cindy Lee Van Dover. Van Dover’s pursuit of deep light began in 1986, when she was at Woods Hole Oceanographic Institution on Cape Cod, casting about for a Ph.D. project. Just a year earlier, explorers had discovered the first vents in the Atlantic, and they had scooped up some of the resident gray shrimp for biologists to study. Van Dover’s adviser, Fred Grassle, had gotten hold of some of the preserved specimens. I had just started as a grad student, and Fred said, ‘Here Cindy, you could use this as a project,’ Van Dover remembers. I was looking at their feeding biology, to figure out how they fit into the whole picture.
