Late Quaternary (24-10 ka BP) environmental history of the Neotropical lowlands inferred from ostracodes in sediments of Lago Peten Itza, Guatemala

We inferred late Pleistocene and early Holocene (24-10 ka BP) environmental conditions in and around Lago Peten Itza, Guatemala from ostracode remains in the lake sediments. Multivariate statistics were run on autecological information for 29 extant ostracode species collected in 63 aquatic ecosystems on the Yucatan Peninsula along a steep, increasing NW-S precipitation gradient and across a large altitudinal range. Conductivity and water depth are the most important factors that shape ostracode communities. Transfer functions were developed and applied to fossil ostracode assemblages in a similar to 76-m sediment core (PI-6, similar to 85 ka) taken in 71 m of water from Lago Peten Itza, to infer past shifts in conductivity and water level. Results suggest climate was cold and wet during the Last Glacial Maximum (LGM). Alternating dry and wet conditions characterized the deglacial. Early Holocene climate was warmer and wetter. The LGM was characterized by low ostracode species richness (4 spp.) and abundance (<940 valves g(-1)), dominance of benthic over nektobenthic taxa, abundant Physocypria globula, conductivity as low as 190 mu S cm(-1), and clay-rich sediments with relatively high total organic carbon and low C/N ratios (<14), suggesting relatively deeper water at the core site associated with abundant precipitation. Greatest water depth at the core site during the LGM occurred late in the period and was similar to 50 m. The deglacial was characterized by drier conditions, higher ostracode species richness (6 spp.) and abundances up to 18,115 valves g(-1), dominance of nektobenthic species, and presence of shallow-water and littoral-zone indicators such as Heterocypris punctata and Strandesia intrepida, conductivity up to 550 mu S cm(-1), C/N ratios as high as 37, and gypsum deposition. Lowest inferred lake depth at the core site during the deglacial was similar to 20 m. The early Holocene was characterized by high numbers of ostracode remains, up to 25,500 valves g(-1), and the presence of L. opesta and P. globula. Cytheridella ilosvayi was absent from late Pleistocene sediments, suggesting it colonized northern Central America during the Holocene.