Temperature and dissolved
oxygen (DO) are two features of the stream which affect how much
aquatic life the stream can support.
The temperature of a stream can be
changed by several things, including:
how much sunlight a stream gets--if it is shaded or not by vegetation
if warm water is being released into the stream by industries
or storm runoff from the cities
- if there are particles in the water, such as dirt or algae,
the temperature can increase because the particle can absorb more
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DO may be affected in the following ways:
- a change in the water temperature
- turbulence in the stream mixes air and water and increases
the DO--water is turbulent when the flow is unstable, such as
over rapids or waterfalls
- organic wastes, such as from a wastewater treatment plant or
food processing plant, may decrease the amount of DO in the stream.
- some nutrients released from farm fertilizers and runoff can
cause algae growth to increase and will eventually lead to decreases
of the DO.
You've seen now that temperature
can change the amount of DO in the water. But why is this important?
Different animals need different amounts of DO
to live. For example, trout are found in cold streams and not in