Assessing nutrient inputs, sediment organic matter sources, and the potential for cyanobacteria in ancient water reservoirs at the Maya city of Ucanal, Guatemala: A glimpse at sustainable water management practices

Although water storage infrastructure was crucial to ancient Maya society, relatively little is known about their potential contamination by biological pathogens and nutrient pollution within ancient Maya cities. At the site of Ucanal, Guatemala, inhabitants created an extensive water infrastructure landscape to manage both supply and drainage. Archaeological, geochemical and paleolimnological data were compiled from stratigraphically excavated and chronologically controlled dried sediments from 3 ancient water reservoirs in Ucanal to investigate potential cyanobacteria contamination from the Late Preclassic to the Terminal Classic periods. Elemental and isotopic analyses of carbon, nitrogen, and phosphorus reveal that none of the 3 reservoirs exhibited nutrient or organic carbon rich environments indicative of or conducive to cyanobacteria or eutrophication, regardless of time period. In addition, δ¹³C data show a common pattern of C₄/CAM plants usage throughout the city core from the Preclassic to Terminal Classic periods, similar to settlement zones and agricultural fields identified elsewhere in the Maya area. These results suggest that inhabitants of Ucanal managed a sustainable water landscape system that remained relatively stable and without excessive nutrient inputs despite population increases at the end of the Classic period.