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Mercury and algal blooms poisoned Maya reservoirs at Tikal

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Enlarge / UC graduate student Brian Lane climbs out of the Perdido Reservoir.

Photo/Nicholas Dunning

For centuries, Tikal was a bustling Maya city in what is now northern Guatemala. But by the late 800s CE, its plazas and temples stood silent, surrounded by mostly abandoned farms. A recent study suggests a possible explanation for its decline: mercury and toxic algal blooms poisoned the water sources that should have carried the city through dry seasons.

Tikal’s Maya rulers built the city’s reservoirs to store water from rain and runoff during the winter months. The pavement of the large plazas in the heart of the city tilted slightly, helping funnel rainwater into the reservoirs. Over the centuries, dust and litter settled into the bottom of the reservoirs, too, providing a record of what the environment around Tikal was like—and what was washing into the city’s water supply. University of Cincinnati biologist David Lentz and his colleagues sampled layers of sediment dating back to the mid-800s, and they found that two of Tikal’s central reservoirs would have been too polluted to drink from.

An X-ray fluorescence spectrometer (which identifies the chemicals in a sample based on how they react to being zapped with an X-ray light) revealed that the sediment on the bottom of the reservoirs was laced with dangerous amounts of mercury. Lentz and his colleagues also found ancient DNA from blue-green algae, or cyanobacteria, which can produce deadly toxins.

The loss of these reservoirs came at the worst possible time for Tikal. In the mid- and late 800s, most of the great cities of the Maya world were already faltering under the weight of growing populations, degrading farmland, and decades of drought. Tikal simply couldn’t survive the collapse of even part of its infrastructure.

But how did the reservoirs get so polluted in the first place?

Painting the walls with poison

“Color was important in the ancient Maya world,” said University of Cincinnati anthropologist Kenneth Tankersley, a co-author of the study. The Maya were especially fond of paint made from a blood-red mineral pigment called cinnabar. Painters used it in colorful murals, builders painted the plaster walls of palaces and temples with it, mourners decorated ceremonial burials with it, and potters even used it to decorate ceramics.

Unfortunately for the Maya, cinnabar is poison. The pretty red mineral, which produces such lovely shades when mixed with iron oxide, is actually mercury sulfide. And Lentz and his colleagues say that over the centuries, mercury leached out of the vibrantly painted walls of Tikal’s most magnificent buildings and flowed straight into its reservoirs.

It had been building up in two of Tikal’s reservoirs for centuries before the city’s final decline. Lentz and his colleagues found toxic levels of mercury in sediment layers dating from 600 CE to 900 CE, based on radiocarbon dating of bits of organic matter mixed into the sediment.

“We were able to find a mineral fingerprint that showed beyond a reasonable doubt that the mercury in the water originated from cinnabar,” said Tankersley.

Rich people problems

Most of the time, polluted urban water supplies are a problem for the poor—think of the London cholera outbreak that kickstarted modern epidemiology, or modern lead pollution in the water supply of Flint, Michigan. But the reservoirs in Tikal watered the political and ceremonial heart of the city, as they resided next door to a palace complex and major temples.

“The drinking and cooking water for the Tikal rulers and their elite entourage almost certainly came from the Palace and Temple Reservoirs,” wrote Lentz and his colleagues. “As a result, the leading families of Tikal likely were fed foods laced with mercury at every meal.”

And ironically, the wealth and power that surrounded the reservoirs poisoned their waters but left the rest of the city’s water supply untouched. The plazas that drained into the Palace and Temple Reservoirs were surrounded by palaces, temples, ballcourts, and cemeteries, all decorated with murals and cinnabar-painted plaster. Two other large reservoirs in less prestigious areas of the city were mercury-free, according to Lentz and his colleagues.

Tikal's Central Acropolis, seen here across the city's Great Plaza, would have drained into the Palace Reservoir.
Enlarge / Tikal’s Central Acropolis, seen here across the city’s Great Plaza, would have drained into the Palace Reservoir.

Kitchen garbage and algal blooms

Deadly blooms of blue-green algae also struck the reservoirs at the city’s elite center and left more ordinary districts untouched. And that, too, is a problem Tikal’s rulers accidentally created for themselves.

Based on the XRF analysis, the two reservoirs had also contained high levels of chemicals called phosphates; that usually means the waters were fouled with food waste, feces, and other organic matter. That would have made the reservoirs pretty gross, but it also provided nutrients that fueled huge blooms of blue-green algae, like Planktothrix and Microcystis.

Phosphate levels in the Palace Reservoir quadrupled between 600 and 830 CE, and it’s not hard to see why. Archaeologists found the remains of an ancient kitchen at the north edge of the Palace Reservoir, where meals would have been prepared for the royal residents of the Central Acropolis, Tikal’s major palace complex.

“Hundreds of years of smoky cooking fires and ceramic plates washed in the reservoir added organic material to the waters,” wrote Lentz and his colleagues. “To make matters worse, the Maya cooks apparently dumped food wastes right outside of the kitchen, as evidenced by the presence of an adjacent midden. During the rainy seasons, effluent from this trash pile would have washed directly into the reservoir.”

Not a drop to drink

The droughts of 820 to 870 CE left the reservoir’s waters receding and stagnant—and thanks to the palace kitchens, also chock-full of phosphates and other organic matter. In other words, the reservoirs became the perfect place for cyanobacteria to thrive in deadly profusion. In those layers of sediment, Lentz and his colleagues found traces of ancient DNA from Planktothrix and Microcystis species.

Both of those types of blue-green algae produce compounds called microcystins, which get released into the water when the algae cells die. Most microcystins are toxic to the liver, but some are also neurotoxins, and they can also irritate the eyes, skin, and throat. They’re deadly at very low concentrations and impervious to the usual water-purification tricks, like boiling.

“With the presence of microcystins in Tikal’s reservoirs, the water could not have been safely consumed,” wrote Lentz and his colleagues.

“A complex tapestry of interwoven calamities”

Even with its other reservoirs still clean, the loss of the Palace and Temple Reservoirs would have been a major blow to Tikal’s infrastructure. The city had no ready access to rivers, lakes, or other water sources, and the local water table lies 200m deep, beyond the reach of ancient Maya technology. And for around 50 years, the people of Tikal endured drier, less predictable rainy seasons and harsher dry seasons, which meant the city really couldn’t spare two large reservoirs.

The water pollution made life harder for Tikal’s residents, who were already struggling with food shortages and other woes. It probably also had political consequences for the city’s rulers, whose elaborate decorations and kitchen garbage had caused the problem in the first place.

Maya rulers were expected to provide clean water and fertile crops by keeping the gods happy. In the late 800s, the people may have taken the foul, poisoned reservoirs and the decades of drought as a sign that their rulers had failed in that all-important duty. It may have seemed that the city and its rulers had fallen out of favor with the gods, and many people may have decided there was little reason to stick around and plenty of reason to leave. By around 950 CE, Tikal was on its way to becoming picturesque ruins.

“This scenario likely played out at other Maya cities dependent on reservoirs,” wrote Lentz and his colleagues. “This study presents new methodologies that can be used to test this hypothesis elsewhere.”

Scientific Reports, 2020 DOI: 10.1038/s41598-020-67044-z  (About DOIs).

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COVID was the leading cause of death in Americans aged 45-54 in 2021

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Enlarge / A woman watches white flags on the National Mall on September 18, 2021 in Washington, DC. Over 660,000 white flags were installed here to honor Americans who have lost their lives to COVID-19 epidemic.

COVID-19 was the third leading cause of death in Americans between March 2020 and October 2021, accounting for one in every eight deaths.

In that time frame, COVID-19 ranked in the top five causes of death for every age group of people older than 15 years. Between January and October 2021, the pandemic disease was the leading cause of death among people 45 to 54 years old.

That’s all according to a study of national death certificate data, published Tuesday in JAMA Internal Medicine by researchers at the National Institutes of Health.

The study found COVID-19 caused roughly 700,000 deaths between March 2020 and October 2021. The pandemic disease trailed only heart disease and cancer, which caused roughly 2.15 million collectively in that time frame. The fourth and fifth deadliest afflictions in the US were accidental deaths—including car crashes, overdoses, and alcohol-related deaths—and stroke, which collectively caused around 624,000 deaths during that period.

The authors, led by Meredith Shiels, an expert in cancer epidemiology and genetics at the National Cancer Institute, broke up the time frame into two sections: the start of the pandemic in March 2020 to December 2020, and January 2021 to October 2021, the last month for which there was complete data. This revealed age-specific trends, likely driven partly by uptake of vaccines and other mitigation efforts.

In the 2020 period, COVID-19 was the second leading cause of death in people aged 85 and over, but, amid high vaccine uptake in this age group, it fell to the third leading cause of death from January to October 2021.

Younger adults saw the opposite trend. For those aged 45 to 54, COVID-19 was the fourth leading cause of death in the 2020 period but jumped to the leading cause of death in 2021. Likewise, in those aged 35 to 44, COVID-19 jumped from the fifth leading cause of death in 2020 to the second leading cause in 2021. And for those aged 15 to 24 and 25 to 34, COVID-19 wasn’t in the top five in 2020, but ranked as the fourth leading cause of death in both age groups in 2021.

For those aged 55 to 84, COVID-19 was the third leading cause of death in both time periods.

The study is limited by the potential for misclassifying deaths on death certificates. But the authors were careful to select a time cutoff that would limit provisional or incomplete data from skewing the findings. That meant, however, that the study did not include deaths from part of the delta wave or the towering omicron wave in January 2022. Since October 2021, around 300,000 additional people in the US have died from COVID-19.

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Russian astronauts use space station to promote anti-Ukraine propaganda

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Enlarge / Cosmonauts Oleg Artemyev, Denis Matveyev, and Sergey Korsakov pose with a flag of the Luhansk People’s Republic on the International Space Station.

The Russian state space corporation responsible for spaceflight activities, Roscosmos, on Monday posted images to its official Telegram channel showing three cosmonauts with the tri-color flags of the Luhansk People’s Republic and the Donetsk People’s Republic.

The photos were taken recently on board the International Space Station and show smiling cosmonauts Oleg Artemyev, Denis Matveyev, and Sergey Korsakov posing with the flags.

“This is a long-awaited day that residents of the occupied areas of the Luhansk region have been waiting for eight years,” the Roscosmos message stated. “We are confident that July 3, 2022, will forever go down in the history of the republic.”

The images and social media posting represent the most blatant use of the International Space Station—which is operated by the United States, Russia, Japan, Canada, and the European Space Agency—for Russian propaganda purposes since the invasion of Ukraine.

Luhansk and Donetsk are two breakaway “quasi-states” in the eastern region of Ukraine known as the Donbas. Ukraine and Russia have battled over the two regions since 2014, as Russia has agitated separatists in the Ukrainian territory. The United Nations does not recognize the two “republics,” and Ukraine has designated them as “temporarily occupied territories.” Fighting has heated up since the Russian invasion of Ukraine in February 2022. This past weekend, Russian forces claimed to have established control over the entire Luhansk region.

A professional relationship

NASA and Roscosmos, as well as other space agencies, have continued cooperating on the International Space Station since the invasion began. Some US officials have suggested that NASA should consider breaking ties with Russia in space due to the atrocities in Ukraine. However, the space agency’s administrator has defended the partnership on the basis that the station flies above geopolitical tensions on Earth. NASA also wants to keep flying the station, as breaking the US segment from the Russian segment would be difficult and potentially fatal to the operation of the orbital facility.

In an interview published Monday in the German publication Der Spiegel, NASA Administrator Bill Nelson reiterated this stance.

“In the midst of the Cold War, when the Soviet Union and the United States were mortal enemies and their nuclear weapons could be used at any time, a US and a Soviet spacecraft met in space in 1975,” Nelson said. “Peaceful cooperation continued even after the collapse of the Soviet Union. Our space shuttle docked with the Russian space station Mir. And then we decided to build the International Space Station together. Both countries are needed for operations, the Russians for propulsion, the Americans for power. We will continue to have a very professional relationship between cosmonauts and astronauts to keep this station alive.”

Nevertheless the provocative actions this weekend by Roscosmos, with its cosmonauts celebrating the so-called liberation of Ukrainian territory, brings the bloody conflict on Earth into space. To some observers, such as former NASA astronaut Terry Virts, Russia’s use of the space station for propaganda purposes is unacceptable.

“I am incredibly disappointed to see cosmonauts and Roscosmos using the International Space Station as a platform to promote their illegal and immoral war, where civilians are being killed every day,” said Virts, who flew side by side with Russians and commanded the space station in 2015. “The space station is supposed to be a symbol of peace and cooperation.”

Virts said NASA has largely been trying to look the other way when it comes to Russian actions, most notably when it comes to Roscosmos chief Dmitry Rogozin, who has made numerous jingoistic statements about the war. But in this case, he said, the agency really cannot afford to.

Seat swap

NASA’s cooperation with Russia may come into greater public focus in a couple of months. At present, a NASA astronaut named Frank Rubio is scheduled to fly on a Russian Soyuz spacecraft to the station in September. Around the same time, a Russian cosmonaut named Anna Kikina is due to fly on a SpaceX Crew Dragon vehicle to the station as part of the seat swap. The arrangement has not been formally agreed to by the US and Russian government.

In his German interview, Nelson defended the swap, saying, “It makes a lot of sense for us. You need both Russians and Americans to operate the space station. What happens if something is wrong with one of our spacecraft? We need the other vehicle as a back-up. And that’s why we will continue to have crew exchanges.”

Such an argument may soon ring hollow, however. Boeing’s Starliner spacecraft may make its first crewed test flight before the end of this year, and if it is successful NASA will have two US spacecraft capable of reaching the station.

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How the Yurok Tribe is bringing back the California Condor

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Enlarge / The California condor is a New World vulture, the largest North American land bird. This condor became extinct in the wild in 1987, but the species has been reintroduced in California and Arizona.

The first California condor to reach Yurok ancestral land in over a century arrived by plane and car in late March of 2022. The small plane that carried Condor 746 had a rough landing, and the bird was irritable. He rattled around in a large dog crate during the three-hour drive to the tribe’s newly built condor facility, in a remote location in Redwood National Park.

Once there, he hopped into the flight pen, a tall enclosure of wire mesh, furnished with log perches and a drinking pool. At 8 years old, Condor 746 is an adult, his naked head bright pink instead of the black found in younger birds. He’s on loan from the captive breeding program at the Peregrine Fund’s World Center for Birds of Prey in Boise, Idaho. His job is to act as the mentor for four juvenile birds who will become the founders of a reborn condor society in Yurok country.

“We have mentors because condors are so social,” says Joe Burnett, California Condor Recovery Program Manager at the Ventana Wildlife Society. Young birds in a pen with no adult will become unruly. “You get the Lord of the Flies syndrome,” says Burnett. He and his colleagues quickly learned that release programs need an adult to serve as a role model and enforce the social hierarchy that is crucial to the flock’s survival.

A few days after 746 arrived, Condor A0, age 2, entered the flight pen. The first thing she focused on was 746, lounging on a perch. Understanding that she was in a safe place, A0 checked out the food—the carcass of a stillborn calf—then flapped onto a perch and fluffed up her feathers, a sign of avian contentment. Three young male condors, tagged A1, A2, and A3, followed. The youngsters had been living together for months at other condor facilities in Boise, Idaho, and San Simeon, California, and they already felt at home with each other.

Condor, known as prey-go-neesh in the native language, is sacred to the Yurok people. The Yurok reservation lies along the Klamath River in northwest California, but much of the tribe’s ancestral land is now in the hands of government agencies or private landowners. The tribe has been working to bring back the California condor since 2003, when a group of elders identified the bird as a keystone species for both culture and ecology, and therefore the most important land-based creature in need of restoration.

Nineteen years after the Yurok made that bold decision, the condors arrived. Elders who had worked toward that pivotal moment watched as Tiana Williams-Claussen, director of the Yurok Wildlife Department, and her colleagues released each newcomer into the pen.

Williams-Claussen’s job is to understand the details of condor biology and to interpret Yurok culture for the wider world. A tribal member, she grew up on the coast near the mouth of the Klamath, and went off to Harvard University. She didn’t set out to be a condor biologist, but when she returned in 2007 with a degree in biochemical sciences, condor restoration was the work her people needed her to do. Williams-Claussen has since spent 14 years living and breathing condors, learning how to handle them, building partnerships with government agencies, and listening to what Yurok elders have to say about the great bird.

The California condor is a critically endangered species: In the 1980s, the total population dwindled to fewer than 30 individuals. Biologists concluded the species’ only chance of survival lay in capturing every living condor in order to breed the birds in captivity, safe from poisons and power lines.

Reintroducing condors to the wild proved difficult, however, and the process became a dramatic lesson for biologists on the importance of parenting and the slow pace of growing up among these long-lived, highly social birds. Scientists learned that time spent with adults was critical to the behavioral development of young condors. They also found that in a species where adults follow and protect their offspring for a year or more after the birds fledge, youngsters pioneering landscapes empty of condors require lots of human babysitting.

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