HISTORIA AMBIENTAL DE UN LAGO ALPINO EN EL CENTRO DE MÉXICO (1230-2010)

Abstract

High altitude lakes, with a low mineralization, alkalinity and nutrient levels, are sensitive ecosystems to natural or anthropogenic disturbances and currently are in risk due to global warming. There are only two high altitude lakes (> 3,800 m asl) in Mexico, La Luna and El Sol, in the Nevado de Toluca crater. Chemical parameters and surface sediment diatom assemblages show differences between both lakes, La Luna has lower pH and mineralization, and in spite of their geographic proximity, each lake has a characteristic diatom assemblage, with lower diatom concentration and species richness in La Luna. In this lake Encyonema perpusillum and Psammothidium helveticum are dominant while in El Sol are Cavinula pseudoscutiformis, Psammothidium levanderi and Aulacoseira distans. This ecological distribution is the basis for the interpretation of the diatom record from La Luna, from a 57 cm long core dated with ²¹⁰Pb y ¹⁴C for which cladocera and magnetic susceptibility data are also available. These proxies allowed identifying the beginning of a trend towards colder and dryer climates around 1350-1510. This period correlates with the Little Ice Age (LIA) in which the coldest and driest conditions were from 1660 to 1760, during the Maunder solar minimum. Cooler and drier conditions are recoded until the begining of the 20th century. Correlation with other paleoenvironmental records show that there was a regional trend to drier climates during the LIA in central Mexico.