Variability of sediment diatom assemblages of Lake Pont-de-Salars on the Viaur River (France)

Limnological surveys from the pelagic zone of Lake Pont-de-Salars were unde rtaken during the 1993-1996 period, which included the emptying of the whol e-lake in summer 1995 and the first post year refilling. This reservoir was warm and monomictic and was determined to vary between oligo- and meso-eut rophic status from year to year. Three sediment cores were collected from t he deepest zone and frozen in situ during the short drying period, just aft er the emptying and before the refilling of the reservoir. Analysis of the relative abundance and vertical distribution of diatom taxa was undertaken. The diatom vertical distribution, evident by visual biostratigraphy, is co nfirmed by the correspondence analysis (CA) despite of absence of sediment dating.