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
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.