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Author Archive: "David Toomey"

How High the Biosphere?

Like stratosphere, troposphere, and mesosphere, atmospheric regions with which it shares part of its name, the biosphere is a shell-shaped zone enveloping our planet. But where the others are made of nitrogen, oxygen, water vapor, and trace gases, the biosphere is made of life. It extends in two directions — up and down — farther than most of us realize, and farther than scientists, until a few years ago, would have thought possible.

In 1830, British naturalist Edward Forbes claimed that because sunlight could not penetrate deeper than 600 meters, photosynthesis below that depth was impossible. No photosynthesis meant no photosynthetic organisms. No photosynthetic organisms meant no basis for a food chain. Life, Forbes concluded, could not exist in the deep ocean. In subsequent years, however, scientists did find life at greater depths, dining on dead and decaying organisms that sank slowly from the sunlit waters above. Such life still depended on sunlight, albeit indirectly, and most scientists continued to believe that all organisms relied on the Sun's energy. In the late 1970s, though, geologists using the research submarine Alvin discovered anemones and fish thriving in the warm ...


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