ocean: The Benthic Realm

The benthic realm refers to the floor of the oceans, extending from the high tide line to the greatest ocean depths. The organisms that live in or on the bottom are called benthos. The benthic realm is subdivided on the basis of depth into the littoral zone, which extends from high tide to a depth of about 200 m (660 ft), and the deep-sea realm. The benthic life forms are both sessile (attached) and motile (mobile). They are distributed from near-shore littoral regions to the ocean depths and play an important role in the food chain. Some benthic life forms live by predation, others sift organic matter from the water, and others scavenge the bottom for organic debris that has settled there. Benthic plants can live only in the euphotic zone, the uppermost 100–200 m (330–660 ft) of the ocean, where sunlight penetrates. Benthic animals that live below the euphotic zone often must depend on the rain of organic debris from above to supply their food needs, and thus the deep regions of the benthic realm are not highly populated except in the areas around hydrothermal vents where chemosynthesis provides an alternative food source.

Sections in this article:

• Introduction
• Importance of the Ocean
• The Pelagic Realm
• The Benthic Realm
• The Ocean as a Biological Environment
• Thermohaline Circulation
• Surface Circulation
• Relationship of the Ocean and the Atmosphere
• Trenches, Plains, and Ridges
• Continental Shelves, Slopes, and Rises
• The World Ocean
• Bibliography

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