Toxic Algae and Mercury Caused the Maya to Abandon Tikal: Study
Wed, April 21, 2021

Toxic Algae and Mercury Caused the Maya to Abandon Tikal: Study


The Maya are the indigenous people of Central America and Mexico. They excelled at hieroglyph writing, pottery, calendar-making, mathematics, and agriculture and left behind an amount of symbolic artwork and impressive architecture. According to TV network History, the Maya Empire was centered in lowlands of what is now Guatemala. One of the cities where the Maya civilization grew was Tikal. However, after hundreds of years of expansion and prosperity, they abandoned the great city of Tikal and researchers have long sought to know why the city collapsed. The question remained unanswered until recently.

Abandoning Tikal in the mid-ninth century CE

A new study of Tikal’s reservoirs provides evidence that toxic algae and mercury may have poisoned the ancient city’s drinking water at a time when it was already struggling with a dry season.

Paleobiologist David Lentz from the Department of Biological Sciences of the University of Cincinnati and the team said that the main research focus of any archeological investigation is to understand the past civilization and how they emerge and falter. Knowing these will provide significant insights into long-term human behavior patterns, such as sustainable environmental interactions and land-use practices. The ancient Maya sets an intriguing example for their study, the team believes.

They added that the Maya abandoned the city of Tikal in the mid-ninth century CE. In their investigations, combining soil geochemistry and ancient DNA (aDNA), they found that extended periods of climatic aridity made the once-powerful political, commercial, and ceremonial hub especially vulnerable as it lacked access to permanent bodies of waters, like rivers or lakes. Their groundwater table, which is the upper level of the underground surface where rocks and soil are permanently saturated with water, was also inaccessible at that time.

Inhabitants depend on reservoirs to provide them water during the dry season. These reservoirs are filled during the rainy season. To improve their water collection process, various paved plazas in Tikal were canted, including those found in the West Plaza, the Plaza of the Seven Temples, and the Great Plaza. The purpose of this is to drain the water into the reservoirs, especially in the Palace Reservoirs and the Temple.

The critical role of the reservoir system

The researchers gathered sediment samples during 2009 and 2010 excavations from the deep strata from within four reservoirs in Tikal, including those in Corriental, Perdido, Temple, and Palace. The team wanted to know how the reservoir system played an important role in sustaining the ancient Maya.

Two of the biggest reservoirs were not just dangerously polluted with metal mercury but also have traces of toxic algal blooms, the study found. The authors attributed the presence of mercury pollution to the mercuric sulfide or the mineral cinnabar. The Maya civilization may have mined the mercury-based ore and mix it with iron oxide to create blood red powder for dye and pigment purposes. The brilliant red coating found in the interiors of almost every high-status burial in the ancient city may have carried special meaning for the Maya. Archeologists have unearthed one grave in the ancient city and it contained about 20 pounds of powdered cinnabar.

Widespread use of cinnabar and mercury-laden powder

People residing in Tikal use cinnabar to an extent, particularly in and around the main palace and the city temples. This, however, resulted in the harmful quantities of mercury-laden powder passing through their reservoirs during heavy rainfall. The researchers said that the cooking and drinking water for the Tikal leaders as well as their elite entourage most certainly come to form the Temple Reservoirs and the Palace. Consequently, the leading families in the ancient city were fed with foods laced with mercury, as reported by Smithsonian Magazine.

Toxic blue-green algae

The study also found another factor why the Maya abandoned Tikal and that is because of the toxic blue-green algae. The aDNA of reservoirs’ sediments showed traces of toxin-producing algae. Even with boiling, the toxic is still resistant, lead author Lentz said.

Two central reservoirs in Tikal during the late 800s were also filled with a nutrient called phosphate that caused the blue-green algae to proliferate. After centuries of smoky ceramic plates and cooking fires washed in the reservoir, though, the high level of phosphate accrued.

Anthropologist Kenneth Tankersley, who co-authored the study, told Smithsonian Magazine that the water would have appeared and tasted nasty and nobody during that period would have wanted that water. Locals were also probably aware that something big had gone wrong with Tikal’s phosphate-filled reservoirs erupted with toxic blue-green algae.



Polluted water supply and dry weather

Lentz and colleagues said that even without the toxic water supply, losing two water stores would have already been devastating for the locals. Previous studies have identified that between 820 and 870 was a period of drought. The timeframe likewise corresponds with the layers of sediment they collected in which the mercury and the blue-green algae were found. Considering the polluted water supply and the dry weather, it may have caused the Maya to think that their rulers failed to appease the gods during that period.

It must have led to a demoralized populace, the authors wrote. Experiencing dwindling food supplies and water, the people may have been more willing to leave behind their homes. Nevertheless, the researchers concluded that the poisoned water alone was not the only reason for the downfall of Tikal. The city’s conversion of the central reservoirs to sickness-inducing places from a life-sustaining one would have symbolically and practically led the abandonment of the historical city.



The former territory of the Maya

The third-largest country in Central America and the former territory of the Maya, Guatemala welcomed 1.32 million international tourists in 2005 and the number grew to 1.78 million in 2018. The country is full of tourist attractions and natural beauties.

Tikal is remote and maybe time-consuming for international travelers but those who visited the city say that Tikal ruins must be included in a Guatemala itinerary. Visitors to Tikal National Park reach over 200,000 a year, according to World Heritage Datasheet. The Park is said to be the main attraction for some 15% of Guatemala’s visitors.

Various Mayan ruins can be seen in Guatemala today but Tikal is among the most impressive ones. No wonder why the kingdom is believed to have been one of the most powerful of the ancient Maya.