Impact d'une crue sur les macroinvertébrés benthiques d'un bras du Rhône

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Summary

The transversal distribution of macroinvertebrates has been studied in an arm of the Rhône River. The data have been collected in October 1982, just before a flood (with discharge 35 times as big as the residual flow) and in November, when the discharge was back to the normal level (30 m3 · s⁻¹).

During the flood, the richnesses in taxa and the numbers of animals diminished to a large extent. Many taxa disappeared, the numbers of only one (Rhithrogena sp.) increased significantly. Modifications in the transverse distribution were noted.

These results are discussed with respect to the consequences of the flood and the biology of the species. We try also to explain how the invertebrates can recolonize the stream after a disturbance such as a flood.