Connections of a River - Connectivity
Continuum Concept (pg 4 of 9)
As the river grows (seventh through tenth
order), energy inputs and organism functions
continue to change. Terrestrial organic matter such
as leaf fall is insignificant in comparison to the
volume of water in a wide river. Increasing
turbidity prevents sunlight from reaching the
streambed, so there are few rooted aquatic plants
in the main channel. In backwaters of floodplain
rivers where turbidity has settled, aquatic plants
may be abundant.
Energy is supplied by dissolved and ultrafine
organic material drifting from upstream reaches.
Drifting phytoplankton and zooplankton contribute
to the food base. Energy is also provided during
flood pulses that bring organic matter from the
floodplain into the main channel.
Fish species commonly found in higher order
rivers are omnivores and plankton feeders. Examples
include carp, buffalo, suckers, and paddlefish.
Catfish rely on their olfactory sense to find food
in turbid water; sight feeders such as smallmouth
bass may not do as well. Stream gradient is usually
very low. Disruptions such as riffles and rapids
are rare. Riffle-spawning fishes such as walleye
migrate up tributaries to find suitable spawning