RESPONSE OF LIPID BIOMARKERS TO CLIMATE AND LAND USE CHANGE IN MID-LATE HOLOCENE SEDIMENTS OF LAGUNA ENCANTADA, CHETUMAL, MEXICO

Lakes are sensitive to climatic fluctuations and preserve geologic records of chemical, physical, and biological changes in systems. Hydroclimate information has been reconstructed from lake sediments to infer regional atmospheric circulation and associated climatic changes. Paleoclimatic reconstructions can provide critical insight on how lake systems and communities that depend on them are affected by increasing temperatures as anthropogenic global warming is superimposed on natural climate variability. Tropical regions like the Yucatan Peninsula are being recognized as important in understanding the dynamics of major climate components, such as the Intertropical Convergence Zone, as they provide detailed records of how temperature changes correspond to rainfall shifts. The aim of this study is to reconstruct paleoclimatic changes in the southeastern Yucatan Peninsula during the Mid to Late Holocene by utilizing organic and stable isotopic biogeochemical analyses of biomarkers preserved in sediments from Laguna Encantada in Chetumal, Mexico. A 4.5-meter sediment core was collected from Laguna Encantada and initial geochemical data (TOC/TS ratios and δ³⁴S_pyrite) show that the lake chemistry changed from marine-influenced to freshwater conditions over the course of ~6,000 years, with the transition period notably around the time of Maya settlement in the region as well as change in regional hydroclimate. I propose to use the abundance and isotopic composition of leaf waxes and glycerol dialkyl glycerol tetraethers to determine shifts in hydroclimate, temperature, salinity and subsequent biotic response to these environmental changes in Laguna Encantada during the Mid to Late Holocene. Results from this study will clarify climate-ecosystem dynamics in an understudied region, which can aid in improving our understanding of tropical freshwater systems projected to suffer consequences of anthropogenic climate change and improve protection of these critical freshwater resources.