NOAA/WDS Paleoclimatology - Lake Peten Itza, Guatemala Inorganic and Organic Geochemical Data

Paleolimnological evidence indicates the ancient Maya transformed lowland terrestrial ecosystems by felling forest vegetation to construct large civic-ceremonial centers and to expand agriculture. Dense human settlements and forest disturbance influenced lacustrine environments by increasing runoff and nutrients, but the effects of intense Maya activities on aquatic ecosystems and how ecosystems responded after depopulation of Mayan cities remains poorly studied. We analyzed a 515-cm-long sediment core from Lake Petén Itzá, lowland Guatemala, to infer paleoenvironmental changes resulting from Maya occupation of the riparian archaeological site of Nixtun-Ch’ich’. Substantial increases in charcoal and fecal stanol concentrations indicate Maya occupation of the Candelaria Peninsula by the late Early Preclassic period beginning ca. 1400 cal yr BCE, despite scant archaeological evidence for settlement at that time. Variations in organic geochemical proxies reveal a period of lake ecosystem alteration in the western arm of the lake during initial construction and later expansion of the city’s unique urban grid in the Middle and Late Preclassic periods. Deforestation, soil erosion, urbanization, and human waste efflux enhanced nutrient delivery to the lake, leading to greater primary productivity. Partial depopulation of the city in the Terminal Preclassic resulted in a decline in lake trophic state. Thereafter, shifts in fecal stanol concentrations throughout the Classic and Postclassic periods suggest relatively low, albeit fluctuating, human population densities. Whereas previous studies of long sediment cores from Petén waterbodies have indicated that massive siltation depressed lacustrine primary production, the core collected near Nixtun-Ch’ich’ shows evidence of ancient Maya lake ecosystem deterioration.