| Authors||Jean Giudicelli, Aref Dia, Pierre Legier|
|Title||Étude hydrobiologique d’und rivière de région méditerranéenne, l’Argens (Var, France). Habtats, hydrochimie, distribution de la faune benthique|
|Journal||Bijdragen tot de Dierkunde|
|Abstract||This is the first almost complete hydrobiological monograph of a water-course in a low altitude Mediterranean coastal drainage basin. Through knowledge of the hydrological and physicochemical peculiarities as well as an analysis of the biocoenoses, an ecological zonation of the river is established.|
The Argens is only 114 km long; it rises from a large karstic spring at an altitude of 270 m. By all its general features (topography, hydrology, geology, climate) it represents a good example of a Mediterranean river. Eleven stations have been investigated. Fifteen physicochemical parameters and 174 species of organisms have been taken into account.
The Argens carries relatively cool waters (summer temperatures seldom exceeding 20 °C) which are well oxygenated and strongly mineralized (high Ca contents and locally high chloride and sulphate contents).
Five animal groups (planarians, Ephemeroptera, Plecoptera, elmid Coleoptera, and Trichoptera), representative for the benthic community, have been used in describing the distribution of the species and the changes in population density along the water-course. The relative position occupied by the species in the Argens, agrees well with that in other European rivers or hydrographic networks. The longitudinal succession of related species manifests itself especially through different degrees of abundance; the zones of overlap are generally important, due to the low altitude of the drainage basin.
Ecological affinities and relations between the 11 stations and 115 selected species have been determined by means of factor analysis (correspondence analysis). Six species clusters have been recognized. The authors outline a zonation for the river which corresponds roughly with the well-known system of longitudinal zonation of running water, viz.: a first cluster characterizes the crenon; a 2nd cluster corresponds to the initial sectors of the rhithral; the 3rd includes the eurythermon and lenitic species, corresponding to a boggy zone inserted in the upper reaches; the 4th cluster characterizes the metarhithron plus the hyporhithron; a 5th is a community transitional between rhithron and potamon; a 6th cluster may be identified as the epipotamon (including possibly the metapotamon too).
Thus, despite the physiographic peculiarities of the Argens, relationships between its species clusters and the classical biocenotic zones, can be clearly demonstrated.
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