Some benthonic life forms live by predation, others sift organic matter from the water, and others scavenge the bottom for organic debris that has settled there. Benthonic 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. The pelagic realm consists of all of the ocean water covering the benthic realm. It is divided horizontally into the neritic, or fertile near-shore, province and the oceanic province. Drifting, free-floating organisms, called plankton, and organisms with poor mobile ability populate the euphotic zone.
Most plankton are microscopic or near-microscopic in size.
Marine organisms capable of self-locomotion are called nektonic life forms. Fish, squid, and whales are examples of marine nekton. Listing from Electric Library , a pay service. Copyright 2001 Infonautics Corporation . All rights reserved.