Structure et fonctionnement des écosystèmes du Haut-Rhône français: 5. Colonisation par les macroinvertébrés de substrats artificiels suspendus en pleine eau ou posés sur le fond

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Summary

The colonization of artificial stony substrates was studied at two stations on the River Rhone. Two baskets were set on the bottom (B) and another two suspended in mid water (S) for 1, 3, 7, 14 or 21 days. The community which developed was different on the bottom (B) from that in mid water (S). The number of taxons stabilized by the 3rd day. One group of organisms (Ephemeroptera, Plecoptera, Diptera, Coleoptera, Trichoptera) was more abundant at S and were the typical colonizers. A second group (Gammarus, Mollusca, Planarians, etc.) was more abundant at B. At once, community structure was stable at S. At B the community was less diversified but more natural at S, because the first stages were poorly represented in B. The suspended substrates (S) fed only by drift material were colonized more richly and regularly, and seemed to resemble more closely the natural benthos at the station, with the exception of Molluscs, Planarians and possibly Gammarus.