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.; MENGO, LUCIANA; PISANI, NERINA; RUIZ, MARCIA; PIOVANO, EDUARDO L.

San Carlos de Bariloche

Congreso; IAL IPA 2022; 2022

IAL e IPA

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 low water levels and high-water salinities while the stage II (1976–2017 CE) is the record ofhigh-water levels and lowwater salinities. Along stage II three sub-stages related to changesin nutrient load were recognized. Sub-stage II A (1976–1983 CE) is characterized by anincrease in primary production proxies and TN mainly related to a humid context and reducedwater salinities. During sub-stage II B (1983–2010 CE) the synchronous increase betweennutrients and primary production proxies matches urban population growth and agricultureexpansion after the 1980s. The record of sub-stage II C (2010–2017 CE) shows an increasein all the proxies because of anthropic influence, despite water lake level variability. Resultsshow that regional hydroclimatic variability acts synergistically with anthropic influenceruling the nutrient fluxes to LP and therefore influencing the eutrophication in the lake.Our results provide tools for developing watershed management policies and adaptationmeasures to current global change under the increasing anthropic pressure and large andrapid hydrological variability in Southeastern South America.