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Farming without the sunshine

Photosynthesis -- the use of light to make plant materials from water and carbon dioxide -- is the primary process underlying food production. But there may be another way. Ocean farmers may be able to raise clams and some other kinds of seafood by feeding them bacteria that grow without need for light.

Instead of using sunshine, these bacteria get their primary energy from hydrogen sulfide. This nasty-scented chemical -- which gives rotten eggs their odor -- is produced naturally in Earth's crust. It also is an industrial pollutant. If it can indeed be the basis for a sea farming industry, a troublesome waste product would become a cheap and abundant resource, helping to produce more food.

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Because these bacteria use chemical energy, rather than light energy, to make organic matter, the process is called chemosynthesis (as opposed to photosynthesis). While biochemists have known about it for a long time, they considered it of minor importance, they considered it of minor importance, compared with photosynthesis, as the mainstay for a community of plants and animals. But in the past few years oceanographers have found that chemosynthesis can support an abundance of life at depths of 2,550 meters where sunshine doesn't penetrate and where remains of plants and animals drifting down from sunlit waters are too sparse to support the thriving communities that live there.

So far, such communities have been found mainly along parts of the Galapagos Rift, a deep sea Pacific rift valley between the Galapagos Islands and Central America. There, like oases in the Sahara, hot water vents support rich communities of clams, mussels, tube worms, and many other marine creatures. The thermal waters carry up natural hydrogen sulfide and teem with bacteria. These bacteria, in turn, are food for the deep sea animals.

While the discovery itself has greatly excited marine biologists, it also has made Holger W. Jannasch, C. D. Taylor, and C. L. Winget at the Woods Hole Oceanographic Institution take a new look at chemosynthesis as a basis for food production. If it can support abundant life in a deep sea desert, can it also support a rich sea farming industry?

Outlining their thinking in the Woods Hole journal Oceanus, Jannasch says the first step is to see if they can grow masses of chemosynthetic bacteria cheaply and efficiently. They also have to determine whether or not these can support edible marine animals -- say clams -- at surface pressures. It is not yet certain that bacteria-eating animals that live under the pressure of 2.5 kilometers of water will thrive at the surface. But, so far as is known now, there are no obvious stumbling blocks to developing what could become an important new food source and an answer to the problem of disposing of a waste chemical that is one of the pollutants responsible for "acid rain."


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