DRIVERS OF REGIME SHIFT IN THE PAMPEAN LAKES: A PALEOLIMNOLOGICAL PERSPECTIVE

CARINA SEITZ; GERARDO M.E. PERILLO; MARIA I. VÉLEZ

Madison, Wisconsin

Encuentro; ASLO-2020 Joint Meeting in Madison, Wisconsin; 2020

ASLO

The Pampean region (Argentina) contains many shallow lakes that provide essential ecosystem services, hence their needs for conservation and protection. Besides their importance, little is known about how Pampean lakes will respond to climate change and anthropic impact. To understand this better, a paleolimnological and paleoenvironmental reconstruction of four shallow lakes strategically located in an arid to semiarid transition zone, was produced. All lakes originated in the Late Holocene. At the beginning they were temporary lakes with clear waters; then at around 500-700 yrs. BP they shifted to a different regime, and became permanent features and sustained turbid waters; main agents of stress include water level, salinity and trophic state as indicated by the diatom record. The timing at which the regime shift occurred is correlated with the Little Ice Age (LIA). The LIA would have produce changes in precipitation seasonality favoring higher winter precipitation by the strengthening of the zonal westerlies. Only two lakes have been affected by anthropic eutrophication. This suggest that these lakes are extremely sensible to changes in precipitation that in turn control water volume and quality.