Identifying the influence of environmental drivers throughout the 20th - 21st centuries in the paleolimnological record of a Pampean lake (Argentina)

COSTAMAGNA INGRID; HALAC SILVANA; MENGO LUCIANA; PISANI NERINA; RUIZ MARCIA; PIOVANO EDUARDO

Bariloche

Conferencia; IAL IPA 2022. Lagos, Memorias del Territorio; 2022

INTERNATIONAL ASSOCIATION OF LIMNOGEOLOGY and INTERNATIONAL PALEOLIMNOLOFY ASSOCIATION

Laguna del Plata (LP; 30°55′ S, 62°51′ W) is a saline lake located in central Argentina linked to the SW margin of Laguna Mar Chiquita (LMC). LMC is the largest saline-lake of South America and an important regional climatic sensor. The environmental variability of LP occurred in the last ca. 80 years was reconstructed through a multi-proxy approach in a sedimentary core with the aim of identifying the influence of both natural and anthropic drivers on the lake functioning. The analysis of instrumental and demographic data along with physicochemical proxies (i.e., MS, carbonates, TOC, CD, TC, TN, TP) allow us to identify two main environmental stages. Stage I (1934?1976 CE) is characterized by low values of nutrients (TN, TP) and primary production proxies (TOC, CD, TC) in agreement with lowwater levels and high-water salinities while the stage II (1976?2017 CE) is the record of high-water levels and lowwater salinities. Along stage II three sub-stages related to changes in nutrient load were recognized. Sub-stage II A (1976?1983 CE) is characterized by an increase in primary production proxies and TN mainly related to a humid context and reduced water salinities. During sub-stage II B (1983?2010 CE) the synchronous increase between nutrients and primary production proxies matches urban population growth and agriculture expansion after the 1980s. The record of sub-stage II C (2010?2017 CE) shows an increase in all the proxies because of anthropic influence, despite water lake level variability. Results show that regional hydroclimatic variability acts synergistically with anthropic influence ruling the nutrient fluxes to LP and therefore influencing the eutrophication in the lake. Our results provide tools for developing watershed management policies and adaptation measures to current global change under the increasing anthropic pressure and large and rapid hydrological variability in Southeastern South America.