| Summary: | This paleolimnological research work was focused on the analysis of the temporal variability of the primary producers community of two close karstic lakes, La Cruz and Lagunillo del Tejo (Cuenca, Spain). Photosynthetic pigments preserved in lake sediments were considered as the most suitable biomarker because of their taxonomic specifity and the accurate understanding of the transference from the water column into sedimentary signal by means of an experimental study about the sedimentation processes carried out over three annual cycles in Lake La Cruz. The multidimensional statistical analysis of the pigments stratigraphic profiles showed the site specific responses to different forcing factors over the last centuries. The detailed analysis of the sedimentary signal indicates that the lake-level changes associated to regional hydroclimatic variability have played a relevant role on the composition of the primary producers commnunity in Lagunillo del Tejo, whereas solar variability has pointed out as forcing factor of the inferred changes of Lake La Cruz primary production, which was characterised by a pigment compositional stability. On the other hand the annually laminated sediment of Lake La Cruz have been shown as an excellent quantitative climatic proxy; calibration analysis of calcite laminae thickness indicated a highly significant correlation with winter rainfall. Winter rainfall anomalies are, in turn, highly correlated with the phase of North Atlantic Oscillation (NAO). Given this strong climatic relationship, an annual winter rainfall reconstruction for the period 1589 A.D. to present was performed. The dominance of nonstationary component at high frecuencies of the climate signal over the last 420 years indicates that the connection between winter rainfall and the NAO is not stable over time and suggest that different patterns, not only NAO, have played a role in determining rainfall variability. __________________________________________________________________________________________________ Este ...
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