Allochthonous Drift from Backwaters to the Main Channel of the Mississippi River

Abstract

Drift in Pool 9 of the Upper Mississippi River was sampled using paired nets suspended at 0.6 m and 2.7 m depths. Diel periodicity in numbers, differences in depth distribution, and differences between sampling months were noted for the drift. Drift coming through large side channels, draining backwater habitats, had mean numbers 10 times larger than that in the main channel of the Mississippi River. This allochthonous drift was largely in transport at night and reflected the backwater area drained and, in part, the benthic communities of backwater lakes. The pulsed inputs of allochthonous drift have been largely ignored and may influence the main stem of a large river ecosystem.