Is Macroinvertebrate Drift a Density-Dependent Mechanism of the Benthos in the Lower Mississippi River?

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In the lower Mississippi River, we sampled drifting and benthic macroinvertebrates each month from November, 1984 to June, 1985. Drift was dominated by hydroids, Chaoborous punctipennis (Diptera), Taphromysis louisianae (Mysidacea), and decapod shrimp. The chief components of the benthic community were tubificid oligochaetes and chironomids. The species composition of the drift was significantly different from that of the benthos, for all but one month. We concluded that drift is not a density-dependent function of the bottom fauna in the lower Mississippi River. This information adds strength to the argument that, in very large rivers, drift may be a separate community from the benthos.