Maya civilization activities caused mercury poisoning in Yucatan lakes

Researchers found that the Maya civilization contaminated two lakes in the Yucatán Peninsula of Mexico with toxic levels of mercury over several centuries.

The study, published in the journal Science Advances, shows that mercury concentrations in the sediment of the lakes at Cobá and Xcach exceeded modern safety limits for aquatic ecosystems. The team led by Matthew Neal Waters from Auburn University in the United States identified specific pollution peaks during the Maya Classic period.

At Cobá, mercury levels spiked between 250 and 400 of our era. The site of Xcach showed multiple pollution episodes between 125 and 200, and again between 535 and 820. The researchers believe these high concentrations resulted from the Maya use of cinnabar, a red mineral containing mercury sulfide. They used this pigment to color temples, murals, and objects, and for use in funeral rites and ceremonies. Sediment cores revealed that this mercury contamination caused a collapse in aquatic life.

During the periods of high pollution, the presence of algae, bacteria, and cyanobacteria dropped significantly. Small crustaceans and freshwater snails also decreased or disappeared from the samples. These changes suggest a major disruption of the lakes' food chains. Because the pollution was localized to these sites and not found in nearby control lakes, the researchers attribute the contamination to human activity rather than atmospheric sources.

Savanna Lee Wooten, a co-author of the study, noted that mercury can accumulate in aquatic organisms, potentially exposing local people through water or fish consumption. While the study does not prove that mercury caused the decline of Maya cities, it identifies a distinct environmental pressure alongside known factors like drought and deforestation. During the Classic period, the city of Cobá housed between 60,000 and 90,000 inhabitants.