CONICET | Buscador de Institutos y Recursos Humanos

Lake sediments archive and integrate the physical, chemical, and biological responses toclimate change. Therefore, their study allows the reconstruction of past environmental andclimatic conditions, and their evolution. These processes can be decoded using a selectionof bioindicators, organisms that overcome taphonomic barriers and can be preserved inlacustrine sediments. Ostracods are one of the most used bioindicators, due their adequatepreservation, high population densities and strong sensitivity to environmental variations. Inthis context, the increasing knowledge about the taxonomy and autecology of many livingspecies, allowed defining modern analogues of fossil assemblages in sedimentary cores,where the palaeoenvironmental signals can be interpreted in terms of climatic changes. Inthis study, we compare the composition of the ostracod assemblages of extant and Holocenelake samples (El Toro [40°19´S, 70°25W] and Cari-Laufquen Chica [41°35´S, 69°25W])from Northern Patagonia Argentina, to establish analogs. Our results reveal a high similaritybetween the composition of extant and Holocene samples, supporting the relevance ofthis taxonomic group as bioindicator. Additionally, it is confirmed that oligomesohaline tomesohaline conditions prevailed during the Holocene. Furthermore, much of the speciessampled in actual limnetic environments have not been until now recorded in sedimentarysequences. This opens up significant research questions: the lack of fossil and sub-fossilrecords of these species is a consequence of a lack of sampling in the region and not a realabsence of the species, or is due to a recent colonization. More comprehensive surveys onboth extant and Holocene environments are needed to clarify this matter.

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