Knife in the water part. 3. Did mercury and cyanobacteria lead to the collapse of the Mayan civilization?

A 2020 study of sediment from four major water reservoirs in Tikal has been published. David Lentz’s team believes that water contamination by mercury, derived from Mayan dyes, and by cyanobacteria, which thrive on substances from human excrement, may have led to the abandonment of the city in the mid-9th century AD. In addition, one has to take into account the significant population growth with simultaneous environmental degradation and droughts during the Late Classic era, from 820-870 AD.

Geochemical studies have shown heavy mercury contamination of bottom sediments from the Late and Late Classic eras in the Temple and Palace reservoirs located in central Tikal. The results correlate with a decline in population density during this period, modeled on data from the archaeological record.

What is Mayom mercury good for?

The ancient Maya used mercury in its pure, liquid form during their rituals. We find it especially in funerary and cave contexts. Most notably, however, mercury is part of cinnabar (HgS), a blood-red mineral that was one of the primary dyes used by the Maya. This is where the famous Red Queen, wife of Pakal the Great of Palenque, got her name – All sprinkled withcinnabar…. Pakal himself was no different. Most of the elite tombs at Tikal also contained considerable amounts of cinnabar. The ruler known as Kaloomte’ Bahlam, laid in burial 160 in group 7F-1, was covered with as much as 10 kg of the powdered mineral. The dye was also used to paint artifacts, but especially architectural decorations.

A nifty water collection system in Tikal

When I first heard the hypothesis that not only the plazas, but also the great pyramids of Tikal were constructed to incorporate them into the water supply system of this vast center, the ingenuity of the Maya aroused my admiration. Even the moisture condensing on their surfaces was supposed to flow into the central water reservoirs, and if you’ve ever been to Tikal, you know for yourself how much water can suddenly appear in the selva.

So the entire Northern Acropolis, which was the main royal necropolis, and the Central Acropolis of Tikal, and between them the Grand Plaza, the Plaza of the Seven Temples and the playing fields, part of the Mundo Perdido, and the four great pyramids I, II, V and the Southern Acropolis (it’s that great forest-covered mountain piled up next to Pyramid V), were in the catchment areas of the Temple and Palace reservoirs – two great reservoirs of water, located in the central part of Tikal. How much of that cinnabar must have flowed down there….

The problem of pollution

The mercury could not have been unaffected by the health and lives of the people who consumed the water. Some samples from the Temple and Palace reservoirs exceed the toxicity thresholds accepted today for freshwater reservoirs by a factor of ten, and most of them date from the Late and Late Classic eras. This was the de facto period of the city’s greatest prosperity.

It was not until this era that the soaring pyramids I, II, III, IV and VI, associated with Maya civilization like cultural icons, were erected. This is the time after the final victory of the Yax Mutul rulers over the Serpent Dynasty (Kaanul) and the unchallenged control of Tikal over the southern Maya Plains. Not surprisingly, elevated amounts of phosphate (_PO43-⁾ were also found in bottom sediment samples from the Temple and Palace reservoirs from this period. About 5 million people may have lived in the southern Maya lowlands at that time. That’s an order of magnitude more than live there today.

Population growth in Tikal in the post-Classic era

Phosphate concentration levels are often used at archaeological sites as an indicator of increased deposition of organic matter, such as food waste and fecal matter. Phosphates bind to the soil and remain there for many centuries. In the Temple and Palace reservoirs, on the banks of which there were kitchens for the residents of the Central Acropolis, phosphate concentrations in the Late Classic period (600-830 AD) increased fourfold (0.80-0.92 µg/g) compared to the Preclassic period (0.20 µg/g), the time before Tikal’s first legendary ruler, Yax Ehb’ Xook, who was buried on the Northern Acropolis in the 2nd century AD.

In the Late Classical era, the Central Acropolis was home to, among others, Yasaw Khan K’awiil I, who defeated Yuknoom Yicha’ak K’ahk of Calakmul in 695 A.D., turning the great wheel of fortune on the Mayan Plains. Centuries of anthropogenic loading: flushing hearths and food scraps enriched the water with organic matter. During the rainy season, sewage from piles of garbage near kitchens flowed directly into the water. Unsurprisingly, concentrations fell during the Late Classical era (830 AD.

Overfertilization of water due to nutrient saturation usually entails the proliferation of cyanobacteria – a problem fairly well known from modern, Polish inland reservoirs, mostly eutrophic. The reservoirs at Tikal were no different. Sequencing of the 16S rRNA gene in microbiome samples from the Temple and Palace reservoirs allowed the identification of dangerous cyanobacteria. Microcystis and Planktothrix produce substances dangerous to humans, such as anatoxin-a, which attacks the nervous system, liver-damaging microcystins, and skin-irritating dermatotoxins, which, if taken internally over a prolonged period, can cause cancer. Microcystins are fairly stable compounds, resistant to cooking, among other things.

Early classical white spots

No study, unfortunately, has been done of the Madeira reservoir, which lies on the outskirts of the complex called the Tikal Citadel, discovered in 2016 using LiDAR. Indeed, the latest research from that area – a description of the Teotihuacan altar, published in early 2025, along with Teotihuacan offerings and deposits of Central Mexican artifacts – confirms the permanent residence of Teotihuanians in the second half of the Early Classic period (Manik IIIa phase – 480-550 AD) in Tikal.

Unfortunately, the cores from the reservoirs were taken in 2009-2010, when the Tikal Citadel was still considered a natural landform (the site is still visible as a hill on the attached map). The presented boundaries of the catchment areas appear inaccurate in this then unexplored area.

Could cyanobacteria and mercury have led to the collapse of the classical Maya civilization?

The ruler’s family of the Yax Mutul dynasty of the time, as well as the upper aristocracy living in the Central Acropolis, were particularly exposed to systematic consumption of mercury and other toxins. David Lentz and his team point to the unhealthy physique of the last ruler of Tikal, which may be the result of prolonged exposure to mercury. His name translates as Eclipse of the Sun. On January 28, 810 AD, he consecrated the penultimate stele known from Tikal, placing it at the base of Pyramid III. On panel 2 from that pyramid he does indeed look like old Baron Harkonnen….

The declining droughts that befell Tikal between 820 and 870 AD would not have been able to single-handedly defeat a state with a healthy environment and a strong backbone of a ruling class. Tikal’s elites, faced with a combination of negative factors such as droughts, mercury contamination of water, and blooms of dangerous cyanobacteria and resulting disease, ceased to meet the requirements established by the social contract. Their loss of causality robbed them of the social legitimacy to govern. The electorate voted with its feet, turning away from them and leaving the city.

Even if Yax Mutal (Tikal) – one of the most important centers of classical Maya civilization – collapsed as a result of the aforementioned factors, this does not explain the decline of other city-states in the southern Maya Plains. The last stele in Tikal was not consecrated until August 17, 869 AD, at the end of the aforementioned droughts, and this was done by Yax Mutul’s ruler Jasaw Khan K’awiil II. Only after this did the city have to be abandoned.

Of course, the aforementioned combination of adversities may have occurred in other Maya centers as well, but certainly not in all of them. The kingdom of B’aakal, with its capital at Lakam Ha’ (Palenque), was perched on three mountain streams, so efficient that only one of them – the Otolum – would have been sufficient to supply water to the entire population there. And yet Palenque had deserted at least two decades earlier. The declining era of Maya civilization had a prelludium in the form of twenty years of wars (810-830 A.D.), which tired everyone out. Because wars, resource depletion and environmental degradation like to play together….

MAIN PHOTO: Przemek Trześniowski Archeophotography

In the article, I used:

1. Baker, Moses Nelson (1981) The Quest for Pure Water: The History of Water Purification from the Earliest Records to the Twentieth Century. American Water Works Association, Denver. ISBN: 978-1258498603
2. Jackson, Marie D.; Sean R. Mulcahy, Heng Chen, Yao Li, Qinfei Li, Piergiulio Cappelletti, Hans-Rudolf Wenk (2017) Phillipsite and Al-tobermorite mineral cements produced through low-temperature water-rock reactions in Roman marine concrete. “American Mineralogist” 102:1435-1450 https://doi.org/10.2138/am-2017-5993CCBY
3. Lentz, David L.; Trinity L. Hamilton, Nicholas P. Dunning, Vernon L. Scarborough, Todd P. Luxton, Anne Vonderheide, Eric J. Tepe, Cory J. Perfetta, James Brunemann, Liwy Grazioso, Fred Valdez, Kenneth B. Tankersley, Alison A. Weiss (2020) Molecular genetic and geochemical assays reveal severe contamination of drinking water reservoirs at the ancient Maya city of Tikal. “Science Reports” 10, 10316. https://doi.org/10.1038/s41598-020-67044-z
4. Scarborough, Vernon L.; Nicholas P. Dunning, Kenneth B. Tankersley, Christopher Carr, Eric Weaver, Liwy Grazioso, Brian Lane, John G. Jones, Palma Buttles, Fred Valdez, David L. Lentz (2012) Water and sustainable land use at the ancient tropical city of Tikal, Guatemala. “Proceedings of National Academy of Science” 109 (31) 12408-12413. https://doi.org/10.1073/pnas.1202881109
5. Tankersley, Kenneth Barnett; Nicholas P. Dunning, Christopher Carr, David L. Lentz, Vernon L. Scarborough (2020) Zeolite water purification at Tikal, an ancient Maya city in Guatemala. “Science Reports” 10, 18021. https://doi.org/10.1038/s41598-020-75023-7