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Whale
Shark
their tissues. At the same time, they give out oxygen, which aerates the water and makes it possible for other life to survive.
The ocean waters also contain all of the nourishment that plants need to develop their tissues, although it may be concentrated
in some places more than others. One place where nourishment is plentiful is where ocean currents rise from the seabed to the surface.
Dolphins
Fish
Octopus
Such places contain more life than anywhere else in the world. A good example is the Peru Current off western South America, where the prevailing winds bring deep water toward the surface. When this upwelling occurs, plankton thrive, and the fish and other animals that depend on them for food also grow in enormous numbers. (See also:
El Niño; Seawater; Water life.)
Meander becomes more pronounced and forms an oxbow loop.
Oxbow, oxbow lake
A bend in a meandering river that almost doubles back on itself and leaves only a narrow neck of land between parts of the channel (see: Meander).
An oxbow lake is a small arc-shaped depression, often containing a crescent-shaped lake. It represents an abandoned oxbow, part of the former course of a river where the narrow neck has been
cut right through. Oxbows are only
found on river flood
plains. For photographs The oxbow loop is of oxbows see page 30.
cut right through
during floods. (See also: Billabong.)
Meander
Seaweeds and anemones
 Ocean life—Oceans have a greater amount
of life than the land. The bottom of the food chain is mainly microscopic plankton. This provides the food for invertebrates such as molluscs, fish, and for mammals such as whales.
An oxbow lake is left behind in the abandoned loop.
 Oxbow, oxbow lake—Oxbows develop as meanders double back on themselves. The diagram sequence at left shows how a meander can then be cut off to create an oxbow lake.
Oxbow, oxbow lake
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