Response of diatoms to Late Quaternary climate changes

Abstract

Diatoms are very useful proxy indicators to reconstruct past climate changes. Studies are based on qualitative and quantitative analyses that allow to infer variables related directly to climate as temperature, or indirectly as salinity, depth, productivity and pH. Reconstructions based on these methods rely on the general assumption that past environmental requirements of the fossil diatom taxa have remained similar to those of their closest living representatives. In this way, the environmental information obtained from living organisms can be used as analogs and extrapolated to the fossil record, particularly in Late Quaternary studies. Diatom records from lacustrine deposits from Argentina, ancient lakes from South America and marine cores from Southeastern Atlantic Ocean and Eastern Equatorial Pacific were reinterpreted with the aim to correlate them to climatic changes during Marine Isotope Stage 3 (MIS 3) in the Southern Hemisphere. Marine records allowed paleo-reconstructions of Productivity and upwelling conditions; at the same time continental records were used to interpret the lake-level histories. The high temporal resolution of diatom assemblages in both environments makes it possible to identify abrupt climate changes between ca. 60 and 30 cal. ka B.P. The future integration of diatom datasets constructed from different environments will solve the analogy problems between fossil and modern assemblages and increase the potential for reliable quantitative reconstructions of Late Quaternary climate in southern South America.