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

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

Congreso; Lagos, Memorias del Territorio-Lakes, Memories of the Landscape IAL-IPA 2022; 2022

Laguna del Plata (LP; 30°55′ S, 62°51′ W) is a saline lake located in central Argentinalinked to the SW margin of Laguna Mar Chiquita (LMC). LMC is the largest saline-lake ofSouth America and an important regional climatic sensor. The environmental variability ofLP occurred in the last ca. 80 years was reconstructed through a multi-proxy approach ina sedimentary core with the aim of identifying the influence of both natural and anthropicdrivers on the lake functioning. The analysis of instrumental and demographic data along withphysicochemical proxies (i.e., MS, carbonates, TOC, CD, TC, TN, TP) allow us to identifytwo main environmental stages. Stage I (1934–1976 CE) is characterized by low values ofnutrients (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.