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Life of a River - Biology
River Continuum Concept: Lower reaches (pg 6 of 7)

Energy inputs and how organisms feed continue to change as the river grows larger (seventh through tenth order). Compared to small streams, large rivers respond more slowly and less dramatically to changes in flow and temperature. Terrestrial debris such as leaf fall is insignificant relative to the volume of water in a wide river.

Increasing turbidity from suspended organic and inorganic particles prevents sunlight from reaching the streambed so there are few rooted aquatic plants or periphyton, except in backwaters and riverine lakes where fine sediment settles. Energy is supplied by dissolved and ultrafine organic material drifting from upstream reaches. Drifting phytoplankton and zooplankton contribute to the food base.

Invertebrates are made up largely of collectors. Larger filter feeders like mussels become more numerous. With the abundant drifting food supply, collectors such as net-spinning caddisflies or burrowing mayflies often reach high densities.

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Copepods

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Introduction
Flow
Shape
Connections
Quality
Life
Description
Terrestrial plants
Terrestrial animals
Life cycles
Corridors
Refuges
Aquatic habitats
Adaptations
Continuum concept
Relationships
Consequences
Stories
Summary
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