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Cladoceran assemblages in a karstic lake as indicators of hydrological alterations

Abstract:

The anthropogenic impact on wetlands has increased during the last centuries when infrastructures such as canals or dams, have proliferated. In this article, we have used cladoceran sub-fossils to investigate the effects of a canal on lake El Tobar (Spain). The canal has been transferring water from a reservoir, built in another valley, into this lake since its construction in the mid-1960s. Cladoceran remains were analyzed in two sediment profiles from each of the two sub-basins of the lake. The sedimentary sequences showed that the mentioned human activity provoked a clear shift in the cladoceran community. A PCA was performed with samples from both sub-basins to detect the direction and nature of the changes. Before water transference, the phytophilous chydorid community, represented by Acroperus angustatus in one sub-basin and by both A. angustatus and Graptoleberis testudinaria in the other sub-basin, were well developed. After the construction of the canal and the inflow of additional yet different water from the reservoir, the proportion of chydorids relative to total cladoceran diminished considerably; this was mainly due to the invasion of Bosmina longirostris. These results indicate that the hydrological alteration caused a shift from an oligotrophic, shallower lake with a rich plant-associated cladoceran community to a more eutrophic lake with a predominant planktonic cladoceran community; and that cladoceran remains are a powerful tool to detect hydrological changes and eutrophication. © 2011 Springer Science+Business Media B.V.