Environmental evolution of the lakes in the arid-semiarid Pampas of Argentina over the last millennium.

SEITZ, C.; VELEZ CAICEDO, M.I.; PERILLO, G.M.E.

Bariloche

Congreso; IAL-IPA 2022. Lakes, Memories of the Past; 2022

IAL-IPA

Many shallow lakes in Argentina’s Pampean region provide essential ecosystem services,encouraging conservation and protection efforts and research regarding their fate in the faceof climate change and human impact. We created a paleolimnological and paleoecologicalreconstruction based on litho-stratigraphy, diatoms, phytoliths, and geochemistry of fourPampean shallow lakes (La Salada, Sauce Grande, Los Chilenos, and Puan). The lakes arestrategically placed along a climate gradient from arid to semiarid conditions. We aimed todetermine the primary causes and mechanisms of long-term ecological change in Pampeanlakes. According to our findings, lakes changed from being temporary with clean waters tobecoming permanent with turbid waters. We argue that an increase in net precipitation causesthis shift by raising lake levels and lake extension, which favored sediment resuspensionand primary productivity. The climatic improvement happened first in the current dry region,at 910 and 593 cal. yr. BP in La Salada and Sauce Grande, respectively, then in the semiaridzone, at 463 cal. yr. BP in Los Chilenos, and lastly in Puan at 20 cal. yr. BP (1930 AD).Secondary drivers of ecological change were salinity (in Puan and La Salada) and nutrients(in Los Chilenos and Sauce Grande). Human-induced eutrophication affected the lakes onlyin recent times. This study demonstrates the significant effect that climate change has onecosystem shift on shallow lakes and alert us about new shifts resulting from the dual impactof climate change and anthropogenic activities.