Environmental changes in Laguna de Yuriria (Central Mexico) using a paleolimnological approach

MANJARREZ-RANGEL CYNTHIA SOLEDAD; ZANOR GABRIELA; HALAC SILVANA; PIOVANO EDUARDO

Bariloche

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

INTERNATIONAL ASSOCIATION OF LIMNOGEOLOGY and INTERNATIONAL PALEOLIMNOLOFY ASSOCIATION

Laguna de Yuriria is a shallow artificial reservoir (4 m depth) located in the state of Guanajuato (20°14? S and 101°07? W, central Mexico). It was built in 1548 over a wetland, becoming the first hydraulic engineering construction of Latin America. Currently, its main functions are agricultural irrigation, fishing, and recreation. Laguna de Yuriria has been receiving water affected by anthropic activities, such as agriculture runoff and wastewater discharge. Until now, the studies have focused on the water quality assessment, with a limited temporal scope. The present study aims to reconstruct the history of environmental changes in Laguna de Yuriria through its sedimentological record and a multi-proxy approach. A sedimentary core (133 cm length) was collected in the center of the reservoir. The proxies analyzed were carbonates (CaCO3), total carbon (TC), total nitrogen (TN), total phosphorus (TP) and the carbon-nitrogen ratio (C:N). Three main environmental stages were identified: Stage 1 isconsidered the environmental base level of the reservoir with the lowest C:N ratio (mean=21.12%) and the highest TC (mean= 3.32%) and TN (mean= 0.17%) content that support the hypothesis of an old wetland. Stage 2 indicates an increase in the limnimetric level and is characterized by a decreased in TC (mean= 2.64%) and TN (mean=0.12%) contents and an increase in C:N ratio (mean= 22.33%), as a response of an increased terrestrial organic material input. Stage 3 is characterized by an increase in CT (mean= 7.13%), NT (mean= 0.47%) and PT (mean= 302.63 mg/kg) with respect to stage 2, indicating a high level of eutrophication, probably related to a higher anthropic impact. This is mainly associated with more urbanization and extensive agricultural activity in the surrounding area. Our findings show pronounced environmental changes in Laguna de Yuriria through time. These results might be useful tools for co-management of this watershed.