Comparative analysis of extant and Holocene ostracod assemblages from Northern Patagonia, Argentina

COVIAGA, CORINA; CUSMINSKY GABRIELA; PEREZ, ALEJANDRA PATRICIA; ARISTEGUI, DANIEL

San Carlos de Bariloche

Congreso; IPA-IAL 2022 Lagos Memorias del Territorio; 2022

Lake sediments archive and integrate the physical, chemical, and biological responses to climate change. Therefore, their study allows the reconstruction of past environmental and climatic conditions, and their evolution. These processes can be decoded using a selection of bioindicators, organisms that overcome taphonomic barriers and can be preserved in lacustrine sediments. Ostracods are one of the most used bioindicators, due their adequate preservation, high population densities and strong sensitivity to environmental variations. In this context, the increasing knowledge about the taxonomy and autecology of many living species, allowed defining "modern analogues" of fossil assemblages in sedimentary cores, where the palaeoenvironmental signals can be interpreted in terms of climatic changes. In this study, we compare the composition of the ostracod assemblages of extant and Holocene lake samples (El Toro [40º19´S, 70º25´W] and Cari-Laufquen Chica [41º35´S, 69º25´W]) from Northern Patagonia Argentina, to establish analogs. Our results reveal a high similarity between the composition of extant and Holocene samples, supporting the relevance of this taxonomic group as bioindicator. Additionally, it is confirmed that oligomesohaline to mesohaline conditions prevailed during the Holocene. Furthermore, much of the species sampled in actual limnetic environments have not been until now recorded in sedimentary sequences. This opens up significant research questions: the lack of fossil and sub-fossil records of these species is a consequence of a lack of sampling in the region and not a real absence colonization. More comprehensive surveys on both extant and Holocene environments are needed to clarify this matter.