Tuesday, February 24, 2026

Peatland lakes in the Congo Basin release carbon that is thousands of years old

ETH Zurich

image:
At the confluence of the Fimi and Kasai rivers in the Democratic Republic of Congo, dark water from forest landscapes meets water from the savannahs, colored red by iron oxides.
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Credit: (Image: Matti Barthel / ETH Zurich)

The vast swamps and peatlands of the tropics play an important role in the global carbon cycle and consequently in the global climate. The Amazon basin, the Congo basin, and the tropical wetlands of Southeast Asia accumulate carbon in the form of dead, undecomposed plant material, storing around 100 gigatonnes of carbon in the process.

One of the largest and most important of these tropical carbon stores is situated in the Congo Basin in the heart of Africa, home to the mighty Congo River and its numerous tributaries. Although the swamps and peatlands of the Congo Basin cover only 0.3 per cent of the Earth's land surface, they hold one third of the carbon stored in tropical peatlands.

Just how great the impact of these peat ecosystems is on the global carbon cycle and climate has hardly been researched, partly because the central Congo Basin remains difficult to access. Boats and pirogues are often the only means of transport for reaching the remote swamps and lakes.

Research uncovers surprises

A research team headed by ETH Zurich has taken a closer look at the Congo Basin in the last decade. In the process, the researchers uncovered several surprises, such as one of the darkest blackwater rivers in the world, the Ruki River (ETH News reported).

In the latest study, which has just been published in the journal Nature Geoscience, the researchers once again focused on water that has been darkened by the leaching of plant debris: Africa's largest blackwater lake, Lac Mai Ndombe, and its smaller neighbour, Lac Tumba – and they once again met with a surprise.

More than four times the size of Lake Constance, the water of Lake Mai Ndombe resembles black tea. The lake is surrounded by extensive swamp forests and virtually untouched lowland rainforest growing on thick peat. Organic matter washed out of decaying plant and soil material from the surrounding swamp and lowland rainforests colours the lake water dark brown.

Ancient carbon released

Now, researchers have shown that large amounts of carbon in the form of CO₂ are emitted into the atmosphere by way of the two lakes.

Contrary to the researchers' expectations, however, only some of the carbon is from recently produced plant matter. Up to 40 per cent of the carbon stems from peat that has accumulated in the surrounding ecosystems over thousands of years. This is shown by age determinations (radiocarbon dating) of the CO₂ dissolved in the lake water.

"We were surprised to find that ancient carbon is being released via the lake," explains lead author Travis Drake, a scientist in the Sustainable Agroecosystem (SAE) group led by ETH Professor Johan Six. "The carbon reservoir has a leak, so to speak, from which ancient carbon is escaping," adds co-author Matti Barthel, research technician in SAE.

Just how is the carbon released?

Until now, research assumed that carbon stored in the peat of the Congo Basin remained bound for a very long time and was only released under certain conditions, such as prolonged droughts.

It remains unclear just how the carbon is mobilised from the undecomposed plant material. The pathways by which the carbon enters the lake water are also still unknown.

Consequently, it is crucial for researchers to find out whether the release of old carbon indicates a destabilising turning point or a natural state of equilibrium that is balanced by new peat deposits.

Is there a risk of the peatlands drying up?

The release of old carbon could indicate a larger problem, namely that environmental changes triggered by climate change are leading to a chain reaction.

If the climate becomes drier, for example, more carbon could be mobilised because the peat dries out more often and for longer periods of time, allowing oxygen to penetrate deeper the peat layers. This promotes the decomposition of once-stable organic matter by microorganisms, with consequences for the global climate as more CO₂ from this huge carbon store is released into the atmosphere.

"Our results help to improve global climate models, because tropical lakes and wetlands have been underrepresented in these models so far," as Six stated.

Water levels have a massive influence on degassing

In addition to investigating the age and origin of the degassed CO₂, the researchers also examined emissions of two other important greenhouse gases from Lake Mai Ndombe, namely nitrous oxide and methane.

In this parallel study, which was published in the Journal of Geophysical Research, the researchers found that water levels, for example, have a strong influence on the volume of methane escaping into the atmosphere.

The higher the water level of the lake, the more effectively microorganisms break down methane. If the water levels are low(er), as is usual during the dry season, methane is broken down less effectively and escapes from the lake in larger quantities.

"Our fear is that climate change will also upset this balance. If droughts become longer and more intense, the blackwater lakes in this region could become significant sources of methane that impact on the global climate," says ETH Professor Jordon Hemingway. "At present we do not know when the tipping point will be reached."

Changes in land use could prove to be serious

But it is not only climate change that could affect the balance. Changes in land use could incur even more serious consequences. According to estimates, the population of the Democratic Republic of Congo is set to triple by 2050. In order to gain arable land, more forest land will be cleared in future.

Deforestation, in turn, promotes drought, which could keep lake levels permanently low. "We all know the analogy whereby forests are the green lungs of the Earth," says Barthel. "They are not only responsible for gas exchange like our lungs, however, but they also evaporate water through their leaves, thereby enriching the atmosphere with water vapour. This promotes cloud formation and precipitation, which in turn feeds rivers and lakes."

The results help to clarify the role of tropical peatlands and blackwater lakes in global climate change. The research is also vital for developing strategies to reduce greenhouse gases and protect wetlands in the Congo Basin and around the equator belt.

These studies were conducted as part of the TropSEDs project led by ETH Zurich and funded by the Swiss National Science Foundation, in collaboration with scientists from the University of Louvain in Belgium and the Democratic Republic of Congo.

Journal

Nature Geoscience

DOI

10.1038/s41561-026-01924-3

Article Title

Millennial-aged peat carbon outgassed by large humic lakes in the Congo Basin

Article Publication Date

23-Feb-2026

Researchers discover how tuberculosis bacteria use a “stealth” mechanism to evade the immune system

Study reveals mycobacteria stiffen cell membranes to avoid destruction, opening new pathways for treatment

Biophysical Society

Mycobacteria and Tuberculosis — image:
Mycobacteria have evolved sophisticated ways to hijack human immune cells and avoid being destroyed. Specifically, they stiffen the internal membrane to prevent the digestive enzymes within lysosomes from destroying the bacteria.
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Credit: Image Courtesy of Ayush Panda

BETHESDA, MD – Scientists have uncovered an elegant biophysical trick that tuberculosis-causing bacteria use to survive inside human cells, a discovery that could lead to new strategies for fighting one of the world's deadliest infectious diseases.

Tuberculosis kills more than a million people each year and remains a major public health crisis, particularly in Asia, Africa and Latin America. The disease is caused by mycobacteria, which have evolved sophisticated ways to hijack human immune cells and avoid being destroyed.

“Tuberculosis is rampant in India,” said Ayush Panda, formerly a graduate student in the laboratory of Mohammed Saleem at the National Institute of Science Education and Research, India. “I grew up in a state where tuberculosis outbreaks are a major problem, and I was always curious about how these diseases spread. That's what drew me to this research.”

The research, which will be presented at the 70th Biophysical Society Annual Meeting in San Francisco from February 21–25, 2026, and was recently posted on bioRxiv, reveals that mycobacteria release tiny packages called extracellular vesicles that fuse with the membranes of immune cells. These vesicles contain specialized lipids—fatty molecules—that make the cell membrane more rigid.

Normally, when our immune cells engulf harmful bacteria, they trap them in a compartment called a phagosome, which then fuses with another compartment called a lysosome. Lysosomes contain digestive enzymes that break down and destroy the bacteria. However, the team discovered that by stiffening the phagosome membrane, mycobacteria prevent this fusion from occurring—essentially building a protective bunker around themselves inside our own cells.

“If the membrane becomes more rigid, it becomes much harder for the phagosome to fuse with the lysosome,” Panda explained. “It's an elegant biophysical mechanism: the bacteria remodel the membrane architecture to escape the very process that would have killed them.” The researchers also found that these vesicles are not limited to infected cells. They can affect nearby immune cells, weakening them even before they come into contact with the bacteria.

What makes this discovery particularly significant is that it represents an entirely new way of understanding how mycobacteria survive. Previous research focused primarily on proteins that the bacteria disrupt. This study takes a lipid-centric approach, showing that the introduction of bacterial lipids into host cell membranes is sufficient to induce immune dysfunction.

“The most surprising finding was when we introduced mycobacterial lipids into membranes that mimic the host phagosome, we saw remarkable physical changes—the membrane properties were completely altered,” Panda said.

The researchers also observed similar extracellular vesicle-mediated membrane effects in Klebsiella pneumoniae and Staphylococcus aureus, suggesting an evolutionarily conserved strategy among pathogens. The findings open several promising avenues for developing new treatments. Researchers could potentially target the proteins involved in the production of these bacterial vesicles or find ways to counteract the membrane-stiffening effects.

“Now that we understand how the bacteria protect themselves, we can start looking for ways to stop them,” Panda said. “If we can block the bacteria from stiffening those membranes, our immune cells might be able to do their job and stop the infection.”

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The Biophysical Society, founded in 1958, is a professional, scientific society established to lead an innovative global community working at the interface of the physical and life sciences, across all levels of complexity, and to foster the dissemination of that knowledge. The Society promotes growth in this expanding field through its Annual Meeting, publications, and outreach activities. Its 6,500 members are located throughout the world, where they teach and conduct research in colleges, universities, laboratories, government agencies, and industry.

Proximity to nuclear power plants associated with increased cancer mortality

Harvard T.H. Chan School of Public Health

Key points:

U.S. counties located closer to operational nuclear power plants (NPPs) have higher rates of cancer mortality than those located farther away, even after accounting for socioeconomic, environmental, and health care factors.

The study is the first of the 21st century to analyze proximity to NPPs and cancer mortality across all NPPs and every U.S. county.

The researchers emphasized that the findings are not enough to establish causality but highlight the need for further research into the potential health impacts of NPPs, especially amid interest in expanding nuclear energy to help solve climate change.

Boston, MA—U.S. counties located closer to operational nuclear power plants (NPPs) have higher rates of cancer mortality than those located farther away, according to a new study led by Harvard T.H. Chan School of Public Health.

The study is the first of the 21st century to analyze proximity to NPPs and cancer mortality across all NPPs and every U.S. county. The researchers emphasized that the findings are not enough to establish causality but do highlight the need for further research into nuclear power’s health impacts.

The study will be published Monday, Feb. 23, 2026, in Nature Communications.

Numerous studies on the potential link between NPPs and cancer have been conducted around the world, with conflicting results. In the U.S., these studies have been rare and limited in their scope, focused on a single NPP and its surrounding community.

To expand the evidence base, the researchers conducted a national assessment of NPPs and cancer mortality between 2000 and 2018 using “continuous proximity.” They used advanced statistical modeling that captured the cumulative impact of all nearby NPPs, rather than just one. The locations and dates of operation of U.S. NPPs—as well as some nearby in Canada—were obtained from the U.S. Energy Information Administration, and county-level data on cancer mortality was obtained from the Centers for Disease Control and Prevention. The researchers controlled for potential confounders in each county, including educational attainment, median household income, racial composition, average temperature and relative humidity, smoking prevalence, BMI, and proximity to the nearest hospital.

The study found that U.S. counties located closer to nuclear power plants experienced higher cancer mortality rates, even after accounting for socioeconomic, environmental, and health care factors. The researchers estimated that over the course of the study period, roughly 115,000 cancer deaths across the U.S. (or about 6,400 deaths per year) were attributable to proximity to NPPs. The association was strongest among older adults.

“Our study suggests that living near a NPP may carry a measurable cancer risk—one that lessens with distance,” said senior author Petros Koutrakis, Akira Yamaguchi Professor of Environmental Health and Human Habitation. “We recommend that more studies be done that address the issue of NPPs and health impacts, particularly at a time when nuclear power is being promoted as a clean solution to climate change.”

The researchers noted that the results are consistent with the results of a similar study they conducted in Massachusetts, which identified elevated cancer incidence among populations living closer to NPPs.

They also noted some limitations to the study, including that it did not incorporate direct radiation measurements and instead assumed equal impact by all NPPs.

Article information

“National Analysis of Cancer Mortality and Proximity to Nuclear Power Plants in the United States,” Yazan Alwadi, Barrak Alahmad, Carolina L. Zilli Vieira, Philip J. Landrigan, David C. Christiani, Eric Garshick, Marco Kaltofen, Brent Coull, Joel Schwartz, John S. Evans, Petros Koutrakis, Nature Communications, February 23, 2026, doi: 10.1038/s41467-026-69285-4

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Harvard T.H. Chan School of Public Health is a community of innovative scientists, practitioners, educators, and students dedicated to improving health and advancing equity so all people can thrive. We research the many factors influencing health and collaborate widely to translate those insights into policies, programs, and practices that prevent disease and promote well-being for people around the world. We also educate thousands of public health leaders a year through our degree programs, postdoctoral training, fellowships, and continuing education courses. Founded in 1913 as America’s first professional training program in public health, the School continues to have an extraordinary impact in fields ranging from infectious disease to environmental justice to health systems and beyond.