The Importance of the Benthos
Nearly seventy-five percent of the surface of the earth is covered by the sea. Of the 197 million square miles of the earth's area, 139 million are the world ocean; the great interconnected complex of the Atlantic, the Pacific, the Indian and the Arctic oceans, the Mediterranean, and the Baltic, the Red, Black, and the White seas; and all the rest. Seventy-one percent of the world is ocean. Of that, ninety-seven percent is more than 200 meters (656 feet), in depth. This is the abyss or benthos, the "deep sea", that covers almost two-thirds of the earth's surface.
The greatest part of the world of water is the deep sea. The inhabitable land is a thin film of living space for creatures who run on its surface, or less often fly above it or burrow underground; but the sea creatures swim and crawl and drift through the whole enormous mass of the ocean water, making the deep sea by far the most extensive environment on our planet.
All of the rich life familiar to humans, the bustling and buzzing crowds of mammals, birds, and insects and the trees, grass, and flowers of the land, as well as the crabs, snails, fish, and algae of the shallow seas, are crowded into a relatively minor portion of the earth's living space.
The far vaster, unseen and, until recently, unapproachable area of the deep sea has its own fauna, and assemblage representing nearly all branches of the animal kingdom from the simplest one-celled protozoans to the higher vetebrates. The darkness, cold, and pressure of the abyssal regions have left their imprint on the creatures that have become a part of that ecosystem.
All the vegetation on all the continents is estimated to produce 40 billion tons of carbohydrates per year, while the plants of the sea produce from 80 to 120 billion tons, but the meadows of the sea are not so conspicuous as those of the land; first, because inhabitants of the sea are rarely as easy to observe as those on land, and, second, because with few exceptions the plants of the sea are too small to be seen without a microscope. These uncounted myriads of little plants, together with the great numbers of tiny animals that feed on them and on each other, form the plankton.
Plankton is the name applied in 1887 by Victor Hensen, a German professor of zoology, to the great company of marine creatures that drift at the mercy of the currents, as distinguished from the nekton, animals like fish and whales that are able to swim against the moving waters, and from the benthos, the plants and animals attached to the bottom or crawling upon it.
There is no clear-cut dividing line between planktonic and nektonic creatures; some of the fish and other marine animals belong to the plankton phase during the early stages of their lives and later are transformed into the nekton status.
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benthos and several other related words.