Deciphering the environmental drivers throughout the 20th and 21st centuries in the paleolimnological record of Laguna del Plata, Laguna Mar Chiquita system, Northern Pampean plain, Argentina

Abstract

Laguna del Plata (LP) is a small, shallow hypereutrophic saline lake which is part of the hydrological system of Laguna Mar Chiquita (LMC) (Córdoba, Argentina). Environmental variability of LP occurred in the last ca. 80 years, was reconstructed through a multi-proxy approach in LP-17-I sedimentary core. The synchronic correspondence of lithological units and physicochemical proxies throughout the paleolimnological record made it possible to identify two main environmental stages. Stage I (1934–1977 CE) records a long drought resulting in low water levels and high-water salinities, while stage II (1977–2017 CE) records a humid phase, high water levels and low water salinity. In stage II we distinguish three sub-stages related to changes in the nutrient load: sub-stage II A (1977–1983 CE), sub-stage II B (1983–2010 CE) and sub-stage II C (2010–2017 CE). Sub-stage II A is characterized by an increase in TN, carbonates, TOC, CD and TC, related to humid context and reduced water salinities rather than anthropic influence. During sub-stage II B, there is a synchronous increase of nutrients and primary production proxies which matches the urban population growth of Córdoba city and the expansion of the agricultural activity after the 1980s, during a favorable hydroclimatic context. During sub-stage II C, the increase of nutrient and primary production proxies was maintained, despite water lake level variability, as a consequence of anthropic influence. Results show that regional hydroclimatic variability can act synergistically with anthropic influence ruling the nutrient fluxes to LP and therefore influencing the eutrophication and primary productivity of the lake. However, our results allowed us to distinguish that stage I and sub-stage II A were mainly dominated by hydroclimatic variability while sub-stage II B and sub-stage II C were mostly governed by anthropic influence. This study contributes to the understanding of the role of natural and anthropic drivers on the environmental dynamics of the LMC hydrological system during the 20th and 21st centuries. These results provide tools for planning activities and improving watershed management policies in the Pampean plain region of Argentina.