Diatoms (diá-tom-os 'cut in half', from diá, 'through' or 'apart'; and the root of tém-n-ō, 'I cut'.) are a major group of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms makeup a significant portion of the Earth's biomass: they generate about 20 - 50 percent of the oxygen produced on the planet each year, take in over 6.7 billion metric tons of silicon each year from the waters in which they live, and contribute nearly half of the organic material found in the oceans. The shells of dead diatoms can reach as much as a half-mile (800m) deep on the ocean floor, and the entire Amazon basin is fertilized annually by 27 million tons of diatom shell dust transported by transatlantic winds from the African Sahara, much of it from the Bodélé Depression, which was once made up a system of fresh-water lakes.
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