Ice shelves fracture under weight of meltwater lakes

When air temperatures in Antarctica rise and glacier ice melts, water can pool on the surface of floating ice shelves, weighing them down and causing the ice to bend. Now, for the first time in the field, CIRES-led research shows that ice shelves don't just buckle under the weight of meltwater lakes -- they fracture. As the climate warms and melt rates in Antarctica increase, this fracturing could cause vulnerable ice shelves to collapse, allowing inland glacier ice to spill into the ocean and contribute to sea level rise.

"Ice shelves are extremely important for the Antarctic Ice Sheet's overall health as they act to buttress or hold back the glacier ice on land," said Alison Banwell, a CIRES scientist in the Earth Science and Observation Center (ESOC) and lead author of the study published today in the Journal of Glaciology. "Scientists have predicted and modeled that surface meltwater loading could cause ice shelves to fracture, but no one had observed the process in the field, until now."

The new work may help explain how the Larsen B Ice Shelf abruptly collapsed in 2002. In the months before its catastrophic breakup, thousands of meltwater lakes littered the ice shelf's surface, which then drained over just a few weeks.

To investigate the impacts of surface meltwater on ice shelf stability, Banwell and her colleagues from the University of Cambridge, University of Oxford, and University of Chicago traveled to the George VI Ice Shelf on the Antarctic Peninsula in November 2019. First, the team identified a depression or "doline" in the ice surface that had formed by a previous lake drainage event where they thought meltwater was likely to pool again on the ice. Then, they ventured out into the frigid landscape on snowmobiles, pulling all their science equipment and safety gear behind on sleds.

Around the doline, the team installed high-precision GPS stations to measure small changes in elevation at the ice's surface, water-pressure sensors to measure lake depth, and a timelapse camera system to capture images of the ice surface and meltwater lakes every 30 minutes.

In 2020, the COVID-19 pandemic brought their fieldwork to a screeching halt. When the team finally made it back to their field site in November 2021, only two GPS sensors and one timelapse camera remained; two other GPS and all water pressure sensors had been flooded and buried in solid ice. Fortunately, the surviving instruments captured the vertical and horizontal movement of the ice's surface and images of the meltwater lake that formed and drained during the record-high 2019/2020 melt season.

GPS data indicate that the ice in the center of the lake basin flexed downward about a foot in response to the increased weight from meltwater. That finding builds upon previous work led by Banwell that produced the first direct field measurements of ice shelf buckling caused by meltwater ponding and drainage.

The team also found that the horizontal distance between the edge and center of the meltwater lake basin increased by over a foot. This was most likely due to the formation and/or widening of circular fractures around the meltwater lake, which the timelapse imagery captured. Their results provide the first field-based evidence of ice shelf fracturing in response to a surface meltwater lake weighing down the ice.

"This is an exciting discovery," Banwell said. "We believe these types of circular fractures were key in the chain reaction style lake drainage process that helped to break up the Larsen B Ice Shelf."

The work supports modeling results that show the immense weight of thousands of meltwater lakes and subsequent draining caused the Larsen B Ice Shelf to bend and break, contributing to its collapse.

Read more at Science Daily

Scientists propose new method for tracking elusive origins of CO2 emissions from streams

A team of researchers from the University of Massachusetts Amherst that specializes in accounting for the carbon dioxide release by streams, rivers and lakes recently demonstrated that the chemical process known as "carbonate buffering" can account for the majority of emissions in highly alkaline waters. Furthermore, carbonate buffering distorts the most commonly used method of tracking the origins of CO2 in streams. The research, published in Global Biogeochemical Cycles, proposes a better method for tracking the origin of riverine CO2 emissions.

Inland waters, including streams, rivers and lakes, account for roughly 5.5 gigatons of CO2 emissions annually -- about 15% of what humans emit.

But current climate models have trouble accounting for this carbon, in part because, says Matthew Winnick, assistant professor of Earth, Geographic and Climate Sciences at UMass Amherst and the paper's lead author, much of this carbon seems to be produced cryptically, through carbonate buffering.

"The process is a little weird," says Winnick. "It acts as a kind of hidden reserve pool of CO2, replenishing carbon that is lost to the atmosphere, and ultimately increasing the amount of CO2 available for off-gassing."

To show how this hidden pool operates, Winnick and his co-author, then-UMass graduate student Brian Saccardi, looked to studies that focused on the carbon content of the oceans.

"Carbonate buffering is a really well-known phenomenon in the ocean," says Winnick, "and even though oceans work differently from inland waters, we were able to borrow the geochemical equations to build a series of models that could account for a wide range of river and stream conditions."

So what is carbonate buffering? It begins with CO2 -- which is everywhere: in the air, in the soil and in water.

When CO2 dissolves in water, it can react to form carbonic acid, which, through further reactions, can then become bicarbonate and carbonate.

This reaction can also run in reverse, which means that high levels of bicarbonate and carbonate can act as reserve pools of CO2, driving emissions.

This entire balance of CO2, water and carbonate is called "carbonate buffering," and the carbonate reserves can be emitted as a greenhouse gas from stream systems.

Indeed, Winnick and Saccardi found that this hidden pool can account for more than 60% of CO2 emissions under alkaline conditions.

There's yet another trick that carbonate buffering has up its sleeve.

In the era of global warming, it is critically important to know both how much carbon is being emitted overall and where this carbon is coming from.

"While we don't think stream emissions contribute to global warming, there is a big question about whether these emissions will change as climate warms, which could amplify warming in the future. To predict changes, we need to know where the CO2 is coming from," says Winnick.

But figuring out which molecule of CO2 came from which source is not a simple task.

To track carbon, especially carbon emitted by bodies of water, scientists often use carbon isotopes, or versions of carbon with different masses, which act as a sort of forensic signature that can indicate the carbon's origin.

However, Winnick and Saccardi discovered that isotope signals in streams are highly sensitive to carbonate buffering reactions.

"The primary way we use isotopes to track sources is through their relationship with CO2 concentrations, but carbonate buffering causes these relationships to break down," says Winnick.

This breakdown can point to the wrong carbon culprit if not properly accounted for.

Read more at Science Daily

Three years later, search for life on Mars continues

In the three years since NASA's Perseverance rover touched down on Mars, the NASA science team has made the daily task of investigating the red planet seem almost mundane.

The rover and its helicopter sidekick Ingenuity have captured stunning images of Mars and collected 23 unique rock core samples along 17 miles of an ancient river delta.

One science team member, University of Cincinnati Associate Professor Andy Czaja, said he sometimes has to remind himself that the project is anything but ordinary.

"This is so cool. I'm exploring another planet," he said.

Czaja teaches in the Department of Geosciences in UC's College of Arts and Sciences. He is a paleobiologist and astrobiologist helping NASA look for evidence of ancient life on Mars using a rover outfitted with custom geoscience and imaging tools with three of his UC graduate students, Andrea Corpolongo, Brianna Orrill and Sam Hall.

Three years into the mission, the rover has performed like a champ, he said.

"Perseverance has excelled. It's been fantastic. It has such capable instrumentation for doing the geology work. It's able to explore distant objects with its zoom lens cameras and can focus on tiny objects at incredible resolution," Czaja said.

Along the way, the mission has recorded a number of firsts: first powered flight, first recorded sounds of Mars, the longest autonomous drive (nearly a half-mile) and new discoveries about the planet's geology, atmosphere and climate.

Czaja was part of the NASA team that decided where on Mars to land the rover. And he remained on the science team that would pore over its daily data and discoveries to decide what the rover should do next.

Among the new discoveries was finding primary igneous rocks in Jezero Crater. These rocks are the hardened result of liquid magma. They offer scientists promising clues about refining the known age of the planet.

Scientists suspect Mars once had long-lived rivers, lakes and streams. Today, water on Mars is found in ice at the poles and trapped below the Martian surface.

Czaja and his student Corpolongo were co-lead authors of a paper published in the Journal of Geophysical Research, Planets that revealed that Mars also may have had hydrothermal systems based on the hydrated magnesium sulfate the rover identified in the volcanic rocks.

"When those rocks cool off and fracture, they become a habitable environment for life," Czaja said.

Corpolongo also led a similar research paper in the same journal co-authored by Czaja detailing the results of the rover's analysis of samples using the SHERLOC deep ultraviolet Raman and fluorescence instrument. Both papers featured contributions from dozens of their fellow NASA researchers on the project.

Samples collected by the rover may finally answer the question about whether we are alone in the universe.

"We have not found any definitive evidence of life in these deposits yet. But if there were fossil microorganisms trapped in the rocks, they would be too small to see with the rover," Czaja said.

Czaja is hopeful funding will be approved for the anticipated Mars Sample Return mission to retrieve the hermetically sealed titanium tubes scientists have spent three years filling with interesting rock cores.

"These hydrated minerals trap water within themselves and record the history of how and when they formed," the study said. "Returning samples of these minerals to Earth would allow researchers to explore the history of Mars' water and climate and possibly evidence of ancient life with the most sensitive instruments possible."

But that was just the beginning. Perseverance began its deliberate exploration from the floor of the crater to the front of the delta, formed by an ancient river or drainage channel where it encountered sedimentary rocks that often contain trapped minerals and another avenue for evidence of ancient life.

And last year the rover made it to the crater's margin in what used to be an enormous lake where it is exploring deposits of magnesium carbonate, which can form geologically or biologically from bacteria.

Czaja said the decision to send Perseverance to Jezero Crater appears to be paying off.

"Absolutely. There were other places we could have gone that might have been just as good," he said. "You won't know until you explore them all. But Jezero was picked for good reason and it has been completely justified."

The helicopter Ingenuity's flying days appear to be over after it sustained rotor damage in January after landing on its 72nd flight. But Perseverance is still going strong. It still has 15 sample tubes at its disposal to capture additional interesting geologic specimens.

Next the rover will make its way out of Jezero Crater to explore the wider area. Czaja said they are likely to find rocks dating back 4 billion years or more. And Mars could harbor stromatolites or rocks that contain evidence of ancient layered mats of bacteria visible to the naked eye. On Earth, these rocks are sometimes found in extreme environments such as geyser basins.

Read more at Science Daily

Confirmation of ancient lake on Mars builds excitement for Perseverance rover's samples

If life ever existed on Mars, the Perseverance rover's verification of lake sediments at the base of the Jezero crater reinforces the hope that traces might be found in the crater.

In new research published in the journal Science Advances, a team led by UCLA and The University of Oslo shows that at some point, the crater filled with water, depositing layers of sediments on the crater floor.

The lake subsequently shrank and sediments carried by the river that fed it formed an enormous delta.

As the lake dissipated over time, the sediments in the crater were eroded, forming the geologic features visible on the surface today.

The periods of deposition and erosion took place over eons of environmental changes, the radar indicates, confirming that inferences about the Jezero crater's geologic history based on Mars images obtained from space are accurate.

"From orbit we can see a bunch of different deposits, but we can't tell for sure if what we're seeing is their original state, or if we're seeing the conclusion of a long geological story," said David Paige, a UCLA professor of Earth, planetary and space sciences and first author of the paper.

"To tell how these things formed, we need to see below the surface."

The rover, which is about the size of a car and carries seven scientific instruments, has been exploring the 30-mile-wide crater, studying its geology and atmosphere and collecting samples since 2021.

Perseverance's soil and rock samples will be brought back to Earth by a future expedition and studied for evidence of past life.

Between May and December 2022, Perseverance drove from the crater floor onto the delta, a vast expanse of 3 billion-year-old sediments that, from orbit, resembles the river deltas on Earth.

As the rover drove onto the delta, Perseverance's Radar Imager for Mars' Subsurface Experiment, or RIMFAX, instrument fired radar waves downward at 10-centimeter intervals and measured pulses reflected from depths of about 20 meters below the surface.

With the radar, scientists can see down to the base of the sediments to reveal the top surface of the buried crater floor.

Years of research with ground-penetrating radar and testing of RIMFAX on Earth have taught scientists how to read the structure and composition of subsurface layers from their radar reflections.

The resulting subsurface image shows rock layers that can be interpreted like a highway road cut.

"Some geologists say that the ability of radar to see under the surface is kind of like cheating," said Paige, who is RIMFAX's deputy principal investigator.

RIMFAX imaging revealed two distinct periods of sediment deposition sandwiched between two periods of erosion.

UCLA and the University of Oslo report that the crater floor below the delta is not uniformly flat, suggesting that a period of erosion occurred prior to the deposition of lake sediments.

The radar images show that the sediments are regular and horizontal -- just like sediments deposited in lakes on Earth.

The existence of lake sediments had been suspected in previous studies, but has been confirmed by this research.

A second period of deposition occurred when fluctuations in the lake level allowed the river to deposit a broad delta that once extended far out into the lake, but has now eroded back closer to the river's mouth.

Read more at Science Daily

Shallow soda lakes show promise as cradles of life on Earth

Charles Darwin proposed that life could have emerged in a "warm little pond" with the right cocktail of chemicals and energy. A study from the University of Washington, published this month in Communications Earth & Environment, reports that a shallow "soda lake" in western Canada shows promise for matching those requirements. The findings provide new support that life could have emerged from lakes on the early Earth, roughly 4 billion years ago.

Scientists have known that under the right conditions, the complex molecules of life can emerge spontaneously. As recently fictionalized in the blockbuster hit "Lessons in Chemistry," biological molecules can be coaxed to form from inorganic molecules. In fact, long after the real-life 1950s-era discovery made amino acids, the building blocks of proteins, more recent work has made the building blocks of RNA. But this next step requires extremely high phosphate concentrations.

Phosphate forms the "backbone" of RNA and DNA and is also a key component of cell membranes. The concentrations of phosphate required to form these biomolecules in the lab are hundreds to 1 million times higher than the levels normally found in rivers, lakes or in the ocean. This has been called the "phosphate problem" for the emergence of life -- a problem that soda lakes may have solved.

"I think these soda lakes provide an answer to the phosphate problem," said senior author David Catling, a UW professor of Earth and space sciences. "Our answer is hopeful: This environment should occur on the early Earth, and probably on other planets, because it's just a natural outcome of the way that planetary surfaces are made and how water chemistry works."

Soda lakes get their name from having high levels of dissolved sodium and carbonate, similar to dissolved baking soda. This occurs from the reactions between water and volcanic rocks beneath. Soda lakes can also have high levels of dissolved phosphate.

Previous UW research in 2019 found that chemical conditions for life to emerge could theoretically occur in soda lakes. The researchers combined chemical models with laboratory experiments to show that natural processes can theoretically concentrate phosphate in these lakes to levels up to 1 million times higher than in typical waters.

For the new study, the team set out to study such an environment on Earth. By coincidence, the most promising candidate was within driving distance. Tucked away at the end of a master's thesis from the 1990s was the highest known natural phosphate level in the scientific literature at Last Chance Lake in inland British Columbia, Canada, about seven hours' drive from Seattle.

The lake is about 1 foot deep and has murky water with fluctuating levels. It sits on federal land at the end of a dusty dirt road on the Cariboo Plateau, in British Columbia ranching country. The shallow lake meets the requirements for a soda lake: a lake above volcanic rock (in this case, basalt) combined with a dry, windy atmosphere that evaporates incoming water to keep water levels low and concentrates dissolved compounds within the lake.

Analysis published in the new paper suggests soda lakes are a strong candidate for the emergence of life on Earth. They also could be a candidate for life on other planets.

"We studied a natural environment that should be common throughout the solar system. Volcanic rocks are prevalent on the surfaces of planets, so this same water chemistry could have occurred not just on early Earth, but also on early Mars and early Venus, if liquid water was present," said lead author Sebastian Haas, a UW postdoctoral researcher in Earth and space sciences.

The UW team visited Last Chance Lake three times from 2021 to 2022. They collected observations in early winter, when the lake was covered in ice; in early summer, when rain-fed springs and snowmelt-fed streams put water at its highest; and in late summer when the lake had almost completely dried up.

"You have this seemingly dry salt flat, but there are nooks and crannies. And between the salt and the sediment there are little pockets of water that are really high in dissolved phosphate," Haas said. "What we wanted to understand was why and when could this happen on the ancient Earth, in order to provide a cradle for the origin of life."

On all three visits the team collected samples of water, lake sediment and salt crust to understand the lake's chemistry.

In most lakes the dissolved phosphate quickly combines with calcium to form calcium phosphate, the insoluble material that makes up our tooth enamel. This removes phosphate from the water. But in Last Chance Lake, calcium combines with plentiful carbonate as well as magnesium to form dolomite, the same mineral that forms picturesque mountain ranges. This reaction was predicted by the previous modeling work and confirmed when dolomite was plentiful in Last Chance Lake's sediments. When calcium turns into dolomite and does not remain in the water, the phosphate lacks a bonding partner -- and so its concentration rises.

"This study adds to growing evidence that evaporative soda lakes are environments meeting the requirements for origin-of-life chemistry by accumulating key ingredients at high concentrations," Catling said.

The study also compared Last Chance Lake with Goodenough Lake, a roughly 3-foot-deep lake with clearer water and different chemistry just a two-minute walk away, to learn what makes Last Chance Lake unique. The researchers wondered why life, present in all modern lakes at some level, was not using up the phosphate in Last Chance Lake.

Goodenough Lake has mats of cyanobacteria that extract or "fix" nitrogen gas from the air. Cyanobacteria, like all other lifeforms, also require phosphate -- and its growing population consumes some of that lake water's phosphate supply. But Last Chance Lake is so salty that it inhibits living things that do the energy-intensive work of fixing atmospheric nitrogen. Last Chance Lake harbors some algae but has insufficient available nitrogen to host more life, allowing phosphate to accumulate. This also makes it a better analog for a lifeless Earth.

"These new findings will help inform origin-of-life researchers who are either replicating these reactions in the lab or are looking for potentially habitable environments on other planets," Catling said.

Read more at Science Daily

Half of world's largest lakes losing water

More than 50 percent of the largest lakes in the world are losing water, according to a groundbreaking new assessment published today in Science . The key culprits are not surprising: warming climate and unsustainable human consumption.

But lead author Fangfang Yao, a CIRES visiting fellow, now a climate fellow at University of Virginia, said the news is not entirely bleak. With this new method of tracking lake water storage trends and the reasons behind them, scientists can give water managers and communities insight into how to better protect critical sources of water and important regional ecosystems.

"This is the first comprehensive assessment of trends and drivers of global lake water storage variability based on an array of satellites and models," Yao said.

He was motivated to do the research by the environmental crises in some of Earth's largest water bodies, such as the drying of the Aral Sea between Kazakhstan and Uzbekistan.

So he and colleagues from the University of Colorado Boulder, Kansas State University, France, and Saudi Arabia created a technique to measure changes in water levels in nearly 2,000 of the world's biggest lakes and reservoirs, which represent 95 percent of the total lake water storage on Earth.

The team combined three decades of observations from an array of satellites with models to quantify and attribute trends in lake storage globally.

Globally, freshwater lakes and reservoirs store 87 percent of the planet's water, making them a valuable resource for both human and Earth ecosystems. Unlike rivers, lakes are not well monitored, yet they provide water for a large part of humanity -- even more than rivers.

But despite their value, long-term trends and changes to water levels have been largely unknown -- until now.

"We have pretty good information on iconic lakes like Caspian Sea, Aral Sea and Salton Sea, but if you want to say something on a global scale, you need reliable estimates of lake levels and volume," said Balaji Rajagopalan, a CIRES fellow, professor of engineering at CU Boulder, and co-author. "With this novel method …we are able to provide insights into global lake level changes with a broader perspective."

For the new paper, the team used 250,000 lake-area snapshots captured by satellites between 1992-2020 to survey the area of 1,972 of Earth's biggest lakes. They collected water levels from nine satellite altimeters and used long-term water levels to reduce any uncertainty. For lakes without a long-term level record, they used recent water measurements made by newer instruments on satellites. Combining recent level measurements with longer-term area measurements allowed scientists to reconstruct the volume of lakes dating back decades.

The results were staggering: 53 percent of lakes globally experienced a decline in water storage. The authors compare this loss with the magnitude of 17 Lake Meads, the largest reservoir in the United States.

To explain the trends in natural lakes, the team leveraged recent advancements in water use and climate modeling. Climate change and human water consumption dominated the global net decline in natural lake volume and water losses in about 100 large lakes, Yao said. "And many of the human and climate change footprints on lake water losses were previously unknown, such as the desiccations of Lake Good-e-Zareh in Afghanistan and Lake Mar Chiquita in Argentina."

Lakes in both dry and wet areas of the world are losing volume. The losses in humid tropical lakes and Arctic lakes indicate more widespread drying trends than previously understood.

Yao and his colleagues also assessed storage trends in reservoirs. They found that nearly two-thirds of Earth's large reservoirs experienced significant water losses.

"Sedimentation dominated the global storage decline in existing reservoirs," said Ben Livneh, also a co-author, CIRES fellow, and associate professor of engineering at CU Boulder. In long-established reservoirs -- those that filled before 1992 -- sedimentation was more important than droughts and heavy rainfall years.

While the majority of global lakes are shrinking, 24 percent saw significant increases in water storage. Growing lakes tend to be in underpopulated areas in the inner Tibetan Plateau and Northern Great Plains of North America and in areas with new reservoirs such as the Yangtze, Mekong, and Nile river basins.

The authors estimate roughly one-quarter of the world's population, 2 billion people, resides in the basin of a drying lake, indicating an urgent need to incorporate human consumption, climate change, and sedimentation impacts into sustainable water resources management.

And their research offers insight into possible solutions, Livneh said. "If human consumption is a large factor in lake water storage decline, then we can adapt and explore new policies to reduce large-scale declines."

Read more at Science Daily

Algae in Swedish lakes provide insights to how complex life on Earth developed

By studying green algae in Swedish lakes, a research team, led by Lund University in Sweden, has succeeded in identifying which environmental conditions promote multicellularity. The results give us new clues to the amazing paths of evolution.

The evolution of multicellular life has played a pivotal role in shaping biological diversity. However, we have up until now known surprisingly little about the natural environmental conditions that favour the formation of multicellular groups.

The cooperation between cells within multicellular organisms has enabled eyes, wings and leaves to evolve. The predominant explanation for why multicellularity evolves is that being in a group enables species to better cope with environmental challenges -- where being in a large group can, for instance, protect cells against being eaten.

"Our results challenge this idea, showing that multicellular groups form, not because they are inherently beneficial, but rather as a by-product of single-celled strategies to reduce environmental stress. In particular, cells produce a range of substances to protect themselves from the environment and these substances appear to prevent daughter cells from dispersing away from their mother cell," says Charlie Cornwallis, biology researcher at Lund University.

To understand how and why single-celled organisms evolve to be multicellular, the scientists experimented on green algae where some species are always single-celled, some are single-celled but become multicellular under certain conditions, while others are always multicellular containing thousands of cells.They could then identify the environmental conditions that promote multicellularity and find out the benefits and costs for organisms. The researchers then combined data with information on the environments that single-celled and multicellular green algae are adapted to across the whole of Sweden.

"I was surprised that there were no benefits or costs to living in multicellular groups. The conditions that individual cells experience can be extremely different when swimming around on their own, to being stuck to other cells and having to coordinate activities. Imagine you were physically tied to your family members, I think it would have quite an effect on you," says Charlie Cornwallis.

The study was conducted in Swedish lakes, and it not only provides information on which green algae occur where, and why -- it also helps us understand the origins of biological diversity that shape the world around us.

Read more at Science Daily

Earth's many new lakes

The number of lakes on our planet has increased substantially in recent decades, according to a unique global survey of 3.4 million lakes that the University of Copenhagen has taken part in. There has been a particular increase in the number of small lakes, which unfortunately, emit large amounts of greenhouse gas. The development is of great importance for Earth's carbon account, global ecosystems, and human access to water resources.

Bacteria and fungi feeding on dead plants and animals at the bottom of a lake emit vast amounts of CO2, methane, nitrous oxide, and other gases. Some of these gases end up in the atmosphere. This mechanism causes lakes to act like greenhouse gas factories. In fact, freshwater lakes probably account for 20% of all global CO2 fossil fuel emissions into Earth's atmosphere. Forecasts suggest that climate change will cause lakes to emit an ever-greater share of greenhouse gases in the future.

This is just one of the reasons why it is important to know how many and how big these lakes are, as well as how they develop. Until now, this information was unknown. Scientific researchers from the University of Copenhagen and other universities have now prepared a more accurate and detailed map of the world's lakes than has ever existed. The researchers mapped 3.4 million lakes and their evolution over the past four decades using high-resolution satellite imagery combined with artificial intelligence.

The survey shows that between 1984 and 2019, the area of global lake surfaces grew by over 46,000 km2 -- slightly more than the surface area of Denmark.

"There have been major and rapid changes with lakes in recent decades that affect greenhouse gas accounts, as well as ecosystems and access to water resources. Among other things, our newfound knowledge of the extent and dynamics of lakes allows us to better calculate their potential carbon emissions," explains Jing Tang, an Assistant Professor at the Department of Biology and co-author of the study, which is now published in Nature Communications.

According to the study's calculations, the annual increase of CO2 emissions from lakes during the period is 4.8 teragrams (10^12, trillion) of carbon -- which equals to the CO2 emission increase of the United Kingdom in 2012.

Small lakes, large CO2 emissions

More and more small lakes (<1 km2) have appeared since 1984. The number of these small lakes is especially important according to the researchers, because they emit the most greenhouse gas in relation to their size. While small lakes account for just 15% of total lake area, they account for 25% of CO2 and 37% of methane emissions. Furthermore, they also contribute to 45% and 59% of the net increases of the lake CO2 and CH4 emissionsover the period 1984-2019.

"Small lakes emit a disproportionate amount of greenhouse gases because they typically accumulate more organic matter, which is converted into gases. And also, because they are often shallow. This makes it easier for gases to reach the surface and up into the atmosphere," explains Jing Tang, who continues:

"At the same time, small lakes are much more sensitive to changes in climate and weather, as well as to human disturbances. As a result, their sizes and water chemistry fluctuate greatly. Thus, while it is important to identify and map them, it is also more demanding. Fortunately, we've been able to do justify that."

The mapping also reveals that there are two main reasons for Earth's many new lakes: climate change and human activities. Reservoirs account for more than half of increased lake area -- i.e., artificial lakes. The other half are primarily created by melting glaciers or thawing permafrost.

New figures sent to the UN

According to the researchers, the new dataset offers a range of regional and global applications.

"I have sent our new greenhouse gas emission estimates to the people responsible for calculating the global carbon budget, those who are behind the UN's IPCC climate reports. I hope they include them in updating the global emission numbers," says Jing Tang.

She adds:

"Furthermore, the dataset can be used to make better estimates of water resources in freshwater lakes and to better assess the risk of flooding, as well as for better lake management -- because lake area impacts biodiversity too."

Read more at Science Daily

Evolution of tree roots may have driven mass extinctions

The evolution of tree roots may have triggered a series of mass extinctions that rocked the Earth's oceans during the Devonian Period over 300 million years ago, according to a study led by scientists at IUPUI, along with colleagues in the United Kingdom.

Evidence for this new view of a remarkably volatile period in Earth's pre-history is reported in the Geological Society of America Bulletin. The study was led by Gabriel Filippelli, Chancellor's Professor of Earth Sciences in the School of Science at IUPUI, and Matthew Smart, a Ph.D. student in his lab at the time of the study.

"Our analysis shows that the evolution of tree roots likely flooded past oceans with excess nutrients, causing massive algae growth," Filippelli said. "These rapid and destructive algae blooms would have depleted most of the oceans' oxygen, triggering catastrophic mass extinction events."

The Devonian Period, which occurred 419 million to 358 million years ago, prior to the evolution of life on land, is known for mass extinction events, during which it's estimated nearly 70 percent of all life on Earth perished.

The process outlined in the study -- known scientifically as eutrophication -- is remarkably similar to modern, albeit smaller-scale, phenomenon currently fueling broad "dead zones" in the Great Lakes and the Gulf of Mexico, as excess nutrients from fertilizers and other agricultural runoff trigger massive algae blooms that consume all of the water's oxygen.

The difference is that these past events were likely fueled by tree roots, which pulled nutrients from the land during times of growth, then abruptly dumped them into the Earth's water during times of decay.

The theory is based upon a combination of new and existing evidence, Filippelli said.

Based upon a chemical analysis of stone deposits from ancient lake beds -- whose remnants persist across the globe, including the samples used in the study from sites in Greenland and off the northeast coast of Scotland -- the researchers were able to confirm previously identified cycles of higher and lower levels of phosphorus, a chemical element found in all life on Earth.

They were also able to identify wet and dry cycles based upon signs of "weathering" -- or soil formation -- caused by root growth, with greater weathering indicating wet cycles with more roots and less weathering indicating dry cycles with fewer roots.

Most significantly, the team found the dry cycles coincided with higher levels of phosphorus, suggesting dying roots released their nutrients into the planet's water during these times.

"It's not easy to peer over 370 million years into the past," said Smart. "But rocks have long memories, and there are still places on Earth where you can use chemistry as a microscope to unlock the mysteries of the ancient world."

In light of the phosphorus cycles occurring at the same time as the evolution of the first tree roots -- a feature of Archaeopteris, also the first plant to grow leaves and reach heights of 30 feet -- the researchers were able to pinpoint the decay of tree roots as the prime suspect behind the Devonian Periods extinction events.

Fortunately, Filippelli said, modern trees don't wreak similar destruction since nature has since evolved systems to balance out the impact of rotting wood. The depth of modern soil also retains more nutrients compared to the thin layer of dirt that covered the ancient Earth.

But the dynamics revealed in the study shed light on other newer threats to life in Earth's oceans. The study's authors note that others have made the argument that pollution from fertilizers, manure and other organic wastes, such as sewage, have placed the Earth's oceans on the "edge of anoxia," or a complete lack of oxygen.

"These new insights into the catastrophic results of natural events in the ancient world may serve as a warning about the consequences of similar conditions arising from human activity today," Fillipelli said.

Read more at Science Daily

Positive childhood experiences of blue spaces linked to better adult well-being

New research based on data from 18 countries concludes that adults with better mental health are more likely to report having spent time playing in and around coastal and inland waters, such as rivers and lakes (also known collectively as blue spaces) as children. The finding was replicated in each of the countries studied.

Mounting evidence shows that spending time in and around green spaces such as parks and woodlands in adulthood is associated with stress reduction and better mental health. However, we know far less about the benefits of blue spaces, or the role childhood contact has in these relationships in later life.

Data came from the BlueHealth International Survey (BIS), a cross-sectional survey co-ordinated by the University of Exeter's European Centre for Environment and Human Health. The current analysis used data from over 15,000 people across 14 European Countries and 4 other non-European countries/regions (Hong Kong, Canada, Australia and California).

Respondents were asked to recall their blue space experiences between the ages of 0-16 years including how local they were, how often they visited them, and how comfortable their parents/guardians were with them playing in these settings, as well as more recent contact with green and blue spaces over the last four weeks, and mental health over the last two weeks.

The research, published in the Journal of Environmental Psychology, found that individuals who recalled more childhood blue space experiences tended to place greater intrinsic value on natural settings in general, and to visit them more often as adults -- each of which, in turn, were associated with better mental wellbeing in adulthood.

Valeria Vitale, Lead author and PhD Candidate at Sapienza University of Rome, said: "In the context of an increasingly technological and industrialized world, it's important to understand how childhood nature experiences relate to wellbeing in later life.

"Our findings suggest that building familiarity and confidence in and around blue spaces during childhood may stimulate an inherent joy of nature and encourage people to seek out recreational nature experiences, with beneficial consequences for adult mental health."

Dr Leanne Martin, Co-author and Postdoctoral Research Associate at the University of Exeter's European Centre for Environment and Human Health, said: "Water settings can be dangerous for children, and parents are right to be cautious. This research suggests though that supporting children to feel comfortable in these settings and developing skills such as swimming at an early age can have previously unrecognised life-long benefits."

Dr Mathew White, Co-author and Senior Scientist at the University of Vienna, said: "The current study is adding to our growing awareness of the need for urban planners and local bodies responsible for managing our green and blue spaces to provide safe, accessible access to natural settings for the healthy mental and physical development of our children.

"If our findings are supported by longitudinal research that tracks people's exposures over the entire life-course, it would suggest that further work, policies and initiatives encouraging more blue space experiences during childhood may be a viable way to support the mental health of future generations."

Read more at Science Daily

Geologist proposes the number of ancient Martian lakes might have been dramatically underestimated by scientists

Lakes are bodies of water fed by rainfall, snowmelt, rivers and groundwater, through which, Earth is teeming with life. Lakes also contain critical geologic records of past climates. Though Mars is a frozen desert today, scientists have shown that Mars contains evidence of ancient lakes that existed billions of years ago, which could contain evidence for ancient life and climate conditions on the red planet. Through a meta-analysis of years of satellite data that shows evidence for lakes on Mars, Dr Joseph Michalski, a geologist in the Department of Earth Sciences, The University of Hong Kong (HKU) proposed that scientists might have dramatically underestimated the number of ancient Martian lakes that once existed.

Michalski and the international team recently published their results in Nature Astronomy, which describe a global analysis of ancient Martian lakes. "We know of approximately 500 ancient lakes deposited on Mars, but nearly all the lakes we know about are larger than 100 km2," explains Michalski. "But on Earth, 70% of the lakes are smaller than this size, occurring in cold environments where glaciers have retreated. These small-sized lakes are difficult to identify on Mars by satellite remote sensing, but many small lakes probably did exist. It is likely that at least 70% of Martian lakes have yet to be discovered." Scientists monitor these small lakes on Earth in order to understand climate change. The missing small lakes on Mars might also contain critical information about past climates.

The recent paper also reports that most known Martian lakes date to a period 3,500 to 4,000 million years ago, but each of the lakes might have lasted only a geologically short time (10,000 to 100,000 years) during this time span. This means that ancient Mars was probably mostly cold and dry as well, but it warmed episodically for short periods of time. Michalski adds, "Because of the lower gravity on Mars and the pervasive, fine-grained soil, lakes on Mars would have been very murky and might not have allowed light to penetrate very deeply, which could present a challenge to photosynthetic life, if it existed."

Lakes contain water, nutrients and energy sources for possible microbial life, including light for photosynthesis. Therefore, lakes are the top targets for astrobiological exploration by Mars Rovers such as NASA's Perseverance rover now on Mars. But Michalski warns, "Not all lakes are created equal. In other words, some Martian lakes would be more interesting for microbial life than others because some of the lakes were large, deep, long-lived and had a wide range of environments such as hydrothermal systems that could have been conducive to the formation of simple life." From this point of view, it might make sense to target large, ancient, environmentally diverse lakes for future exploration.

"Earth is host to many environments that can serve as analogs to other planets. From the harsh terrain of Svalbard to the depths of Mono Lake -- we can determine how to design tools for detecting life elsewhere right here at home. Most of those tools are aimed at detecting the remains and residues of microbial life," said Dr David BAKER, an ecologist at HKU School of Biological Sciences who is well-informed about the Earth's microbial systems in lakes.

China successfully landed its first lander, Zhurong, on Mars in May this year. Zhurong is currently roving the plains of Utopia Planitia, exploring mineralogical and chemical clues to recent climate change. China is also planning a sample return mission likely to occur at the end of this decade, which could target one of the interesting lake deposits.

Read more at Science Daily

Traces of an ancient road in a lake

Anyone traveling from the German city of Brandenburg via Berlin to Frankfurt an der Oder at the Polish-German border does so along an ancient route that reaches far into Poland. German and Polish researchers have now documented the influence of this East-West connection on the history of the landscape by examining the sediments of Lake Czechowskie in the Bory Tucholskie and also evaluating historical sources. According to the results, three phases of landscape development can be distinguished in the last eight hundred years: from an almost untouched landscape through an intermediate phase lasting several centuries -- characterized by alternations between strong settlement activity and the return of nature after wars -- to today's cultural landscape.

One of the two main authors, Achim Brauer of the GFZ German Research Centre for Geosciences in Potsdam, says: "Wars had a clear influence, as the Via Marchionis was repeatedly used for troop transports that led to local destruction and devastation. In this study, for the first time, we have shown the impact on the landscape for every war in the region's history. In general, wars have led to greater or lesser devastation ('renaturalization') of the landscape, which has also lasted for varying lengths of time."

At other times, it was political developments that left their mark on the landscape, such as an agrarian reform in 1343, which led, with a certain time lag, to an accelerated "anthropogenization" of the landscape, that is, to clearly visible human influence. In the sediments of Lake Czechowskie this is shown by a strong increase of rye pollen and the decrease of birch and pine pollen.

Because sediments in a lake exhibit annual stratification similar to tree rings, the German-Polish team was able to pinpoint the year from which pollen originated by counting the individual layers ("warves") down to a resolution of five years. According to this, the landscape remained largely untouched by humans until about 1350 AD. Extensive forests and natural grasses dominated. Then followed five turbulent centuries. The expansion of agriculture and the formation of larger towns were favored by a warm climate and politically calm times. However, between 1409 and 1435 there was war between the Teutonic Order and Poland -- fields became fallow land, forests expanded again. After peace was concluded, five quiet decades followed again, during which an increase in handicrafts was also evident. Hardwood was cut to obtain building material and potash -- thus, birch pollen disappeared from lake sediments, rye again increased massively.

Huge army campaigns with thousands of riders and foot soldiers, plague epidemics in several waves and some very cold years with crop failures are also documented. Then, from the middle of the 19th century, the influence of agriculture, settlements and economic activity took over to such an extent that one can speak of a predominantly human influence, which continues to this day.

Read more at Science Daily

Lakes are changing worldwide: Human activities to blame

International research led by Luke Grant, Inne Vanderkelen and Prof Wim Thiery of the VUB research group BCLIMATE shows that global changes in lake temperature and ice cover are not due to natural climate variability and can only be explained by massive greenhouse gas emissions since the Industrial Revolution. The influence of human-induced climate change is evident in rising lake temperatures and in the fact that the ice cover forms later and melts sooner.

"These physical properties are fundamental to lake ecosystems," says Grant, a researcher at VUB and lead author of the study. "As impacts continue to increase in the future, we risk severely damaging lake ecosystems, including water quality and populations of native fish species. This would be disastrous for the many ways in which local communities depend on lakes, ranging from drinking water supply to fishing."

The team also predicted future development under different warming scenarios. In a low-emission scenario, the average warming of lakes in the future is estimated to stabilise at +1.5°C above pre-industrial levels and the duration of ice cover to be 14 days shorter. In a high-emission world, these changes could lead to an increase of +4.0 °C and 46 fewer days of ice.

At the beginning of the project, the authors observed changes in lakes around the world: temperatures are rising and seasonal ice cover is shorter. However, the role of climate change in these trends had not yet been demonstrated.

"In other words, we had to rule out the possibility that these changes were caused by the natural variability of the climate system," says fellow VUB researcher and study co-author Vanderkelen.

The team therefore developed multiple computer simulations with models of lakes on a global scale, on which they then ran a series of climate models. Once the team had built up this database, they applied a methodology described by the Intergovernmental Panel on Climate Change (IPCC). After determining the historical impact of climate change on lakes, they also analysed various future climate scenarios.

The results show that it is highly unlikely that the trends in lake temperatures and ice cover in recent decades can be explained solely by natural climate variability. Moreover, the researchers found clear similarities between the observed changes in lakes and model simulations of lakes in a climate influenced by greenhouse gas emissions.

"This is very convincing evidence that climate change caused by humans has already impacted lakes," says Grant. Projections of lake temperatures and ice cover loss unanimously indicate increasing trends for the future. For every 1°C increase in global air temperature, lakes are estimated to warm by 0.9°C and lose 9.7 days of ice cover. In addition, the analysis revealed significant differences in the impact on lakes at the end of the century, depending on the measures taken by humans to combat climate change.

Read more at Science Daily

Icy clouds could have kept early Mars warm enough for rivers and lakes

One of the great mysteries of modern space science is neatly summed up by the view from NASA's Perseverance, which just landed on Mars: Today it's a desert planet, and yet the rover is sitting right next to an ancient river delta.

The apparent contradiction has puzzled scientists for decades, especially because at the same time that Mars had flowing rivers, it was getting less than a third as much sunshine as we enjoy today on Earth.

But a new study led by University of Chicago planetary scientist Edwin Kite, an assistant professor of geophysical sciences and an expert on climates of other worlds, uses a computer model to put forth a promising explanation: Mars could have had a thin layer of icy, high-altitude clouds that caused a greenhouse effect.

"There's been an embarrassing disconnect between our evidence, and our ability to explain it in terms of physics and chemistry," said Kite. "This hypothesis goes a long way toward closing that gap."

Of the multiple explanations scientists had previously put forward, none have ever quite worked. For example, some suggested that a collision from a huge asteroid could have released enough kinetic energy to warm the planet. But other calculations showed this effect would only last for a year or two -- and the tracks of ancient rivers and lakes show that the warming likely persisted for at least hundreds of years.

Kite and his colleagues wanted to revisit an alternate explanation: High-altitude clouds, like cirrus on Earth. Even a small amount of clouds in the atmosphere can significantly raise a planet's temperature, a greenhouse effect similar to carbon dioxide in the atmosphere.

The idea had first been proposed in 2013, but it had largely been set aside because, Kite said, "It was argued that it would only work if the clouds had implausible properties." For example, the models suggested that water would have to linger for a long time in the atmosphere -- much longer than it typically does on Earth -- so the whole prospect seemed unlikely.

Using a 3D model of the entire planet's atmosphere, Kite and his team went to work. The missing piece, they found, was the amount of ice on the ground. If there was ice covering large portions of Mars, that would create surface humidity that favors low-altitude clouds, which aren't thought to warm planets very much (or can even cool them, because clouds reflect sunlight away from the planet.)

But if there are only patches of ice, such as at the poles and at the tops of mountains, the air on the ground becomes much drier. Those conditions favor a high layer of clouds -- clouds that tend to warm planets more easily.

The model results showed that scientists may have to discard some crucial assumptions based on our own particular planet.

"In the model, these clouds behave in a very un-Earth-like way," said Kite. "Building models on Earth-based intuition just won't work, because this is not at all similar to Earth's water cycle, which moves water quickly between the atmosphere and the surface."

Here on Earth, where water covers almost three-quarters of the surface, water moves quickly and unevenly between ocean and atmosphere and land -- moving in swirls and eddies that mean some places are mostly dry (the Sahara) and others are drenched (the Amazon). In contrast, even at the peak of its habitability, Mars had much less water on its surface. When water vapor winds up in the atmosphere, in Kite's model, it lingers.

"Our model suggests that once water moved into the early Martian atmosphere, it would stay there for quite a long time -- closer to a year -- and that creates the conditions for long-lived high-altitude clouds," said Kite.

NASA's newly landed Perseverance rover should be able to test this idea in multiple ways, too, such as by analyzing pebbles to reconstruct past atmospheric pressure on Mars.

Understanding the full story of how Mars gained and lost its warmth and atmosphere can help inform the search for other habitable worlds, the scientists said.

Read more at Science Daily

Reliably measuring oxygen deficiency in rivers or lakes

 When wastewater from villages and cities flows into rivers and lakes, large quantities of fats, proteins, sugars and other carbon-containing, organic substances wind up in nature together with the fecal matter. These organic substances are broken down by bacteria that consume oxygen. The larger the volume of wastewater, the better the bacteria thrive. This, however, means the oxygen content of the water continues to decrease until finally the fish, muscles or worms literally run out of air. This has created low-oxygen death zones in many rivers and lakes around the world.

No gold standard for measurements until now

In order to measure how heavily the waters are polluted with organic matter from feces, government bodies and environmental researchers regularly take water samples. One widely used measurement method uses a chemical reaction to determine the content of organic substances. As an international team of scientists now shows, this established method provides values from which the actual degree of the water pollution can hardly be derived. Prof. Helmuth Thomas, Director of Hereon's Institute of Carbon Cycles is also a contributor to the study, which has now been published in the scientific journal Science Advances. "In the paper, we are therefore also introducing a new method for making the measurements much more reliable in the future," he says.

Using the conventional measurement method, water samples are mixed with the chemicals permanganate or dichromate. These are especially reactive and break down all organic substances in a short time. The quantity of consumed permanganates or dichromates can then be used to determine how much organic substance was contained in the water sample. Experts refer to this measurement as "chemical oxygen demand," COD. The problem with the COD measurements is that they do not differentiate between the organic substances that wind up in the water with the sewage, and those that arise naturally -- such as lignin and humic acids -- which are released when wood decays. This means that the water pollution can hardly be distinguished from the natural content of organic substances. "For the Han River in South Korea, for example, we have shown that the pollution with organic substances from wastewater in the past twenty-five years has decreased. The COD measurements, however, still show high values as they were before," says Helmuth Thomas, "because here the natural substances make up a large portion of the organic matter in the water."

Complicated biological analysis

But how can the actual pollution be measured more reliably? A biological measurement method has been established here for decades, but it is much more complex than the COD method and is therefore used more seldomly by government bodies and research institutions. In this case, a water sample is taken from the river or lake and the oxygen content of the water is measured as an initial value. Another "parallel sample" is immediately sealed airtight. Then this water sample rests for five days. During this time, the bacteria break down the organic substance, whereby they gradually consume the oxygen in the water. After five days, the container is opened and the oxygen is measured. If the water contains a great deal of organic matter, then the bacteria were particularly active. The oxygen consumption was then correspondingly high. Experts refer to the "biological oxygen demand" (BOD) in this measurement. "The BOD measurement is far more precise than the COD because the bacteria preferentially break down the small organic molecules from the wastewater but leave the natural ones, such as lignin, untouched," says Thomas. Nevertheless, the BOD measurement has its disadvantages, too. On the one hand, the BOD measurement takes five days, while the COD value is available after a few minutes. On the other, while filling, storing and measuring the water samples, meticulous care must be taken to ensure that no oxygen from the ambient air winds up in the sample and falsifies the measurement value. "Only a few people with a great deal of laboratory experience have mastered how to entirely handle the BOD measurement," says Thomas. "Therefore, government bodies and researchers even today still prefer the COD despite its greater uncertainties."

Read more at Science Daily

Researchers discover new type of ancient crater lake on Mars

 Researchers from Brown University have discovered a previously unknown type of ancient crater lake on Mars that could reveal clues about the planet's early climate.

In a study published in Planetary Science Journal, a research team led by Brown Ph.D. student Ben Boatwright describes an as-yet unnamed crater with some puzzling characteristics. The crater's floor has unmistakable geologic evidence of ancient stream beds and ponds, yet there's no evidence of inlet channels where water could have entered the crater from outside, and no evidence of groundwater activity where it could have bubbled up from below.

So where did the water come from?

The researchers conclude that the system was likely fed by runoff from a long-lost Martian glacier. Water flowed into the crater atop the glacier, which meant it didn't leave behind a valley as it would have had it flowed directly on the ground. The water eventually emptied into the low-lying crater floor, where it left its geological mark on the bare Martian soil.

The type of lake described in this study differs starkly from other Martian crater lakes, like those at Gale and Jezero craters where NASA rovers are currently exploring.

"This is a previously unrecognized type of hydrological system on Mars," Boatwright said. "In lake systems characterized so far, we see evidence of drainage coming from outside the crater, breaching the crater wall and in some cases flowing out the other side. But that's not what is happening here. Everything is happening inside the crater, and that's very different than what's been characterized before."

Importantly, Boatwright says, the crater provides key clues about the early climate of Mars. There's little doubt that the Martian climate was once warmer and wetter than the frozen desert the planet is today. What's less clear, however, is whether Mars had an Earthlike climate with continually flowing water for millennia, or whether it was mostly cold and icy with fleeting periods of warmth and melting. Climate simulations for early Mars suggest temperatures rarely peaking above freezing, but geological evidence for cold and icy conditions has been sparse, Boatwright says. This new evidence of ancient glaciation could change that.

"The cold and icy scenario has been largely theoretical -- something that arises from climate models," Boatwright said. "But the evidence for glaciation we see here helps to bridge the gap between theory and observation. I think that's really the big takeaway here."

Boatwright was able to map out the details of the crater's lake system using high-resolution images taken by NASA's Mars Reconnaissance Orbiter. The images revealed a telltale signature of ancient streambeds -- features called inverted fluvial channels. When water flows across a rocky surface, it can leave behind course-grained sediment inside the valley it erodes. When these sediments interact with water, they can form minerals that are harder than the surrounding rock. As further erosion over millions of years whittles the surrounding rock away, the mineralized channels are left behind as raised ridges spidering across the landscape. These features, along with sediment deposits and shoreline features, clearly show where water flowed and ponded on the crater floor.

ut without any sign of an inlet channel where water entered the crater, "the question becomes 'how did these get here?"' Boatwright said.

To figure it out, Boatwright worked with Jim Head, his advisor and a research professor at Brown. They ruled out groundwater activity, as the crater lacked telltale sapping channels that form in groundwater systems. These channels usually appear as short, stubby channels that lack tributaries -- completely opposite from the dense, branching networks of inverted channels observed in the crater. A careful examination of the crater wall also revealed a distinct set of ridges that face upward toward the crater wall. The features are consistent with ridges formed where a glacier terminates and deposits mounds of rocky debris. Taken together, the evidence points to a glacier-fed system, the researchers concluded.

Subsequent research has shown that this crater isn't the only one of its kind. At this month's Lunar and Planetary Science Conference, Boatwright presented research revealing more than 40 additional craters that appear to have related features.

Head says that these new findings could be critical in understanding the climate of early Mars.

Read more at Science Daily

Glitter litter could be damaging rivers

 New research indicates that glitter could be causing ecological damage to our rivers and lakes.

The study, led by Dr Dannielle Green of Anglia Ruskin University (ARU) and published in the Journal of Hazardous Materials, is the first to examine the impact of glitter on freshwater habitats.

The research found that after 36 days, the presence of glitter halved the root length of common duckweed (Lemna minor), while levels of chlorophyll in the water were three times lower than in control conditions, indicating reduced levels of phytoplankton, or microalgae.

Glitter is used in a variety of decorative ways, including on clothing, in arts and crafts, and in cosmetics and body paint. Traditional glitter is a form of microplastic consisting of a plastic core made of polyester PET film, which is coated with aluminium and then covered with another thin plastic layer.

Along with other forms of single use microplastics, such as microbeads, there have been efforts to phase out PET glitter with the introduction of more biodegradable alternatives.

One version has a core of modified regenerated cellulose (MRC), sourced mainly from eucalyptus trees, but this is still coated with aluminium for reflectivity and then topped with a thin plastic layer. Another form is mica glitter, which is increasingly used in cosmetics.

However, this new study found that the effects of MRC and mica glitters on root length and chlorophyll levels were almost identical to those of traditional glitter.

The only significant difference was a two-fold increase in the abundance of New Zealand mud snails (Potamopyrgus antipodarum) in water containing the biodegradable MRC glitter. These snails, commonly found in polluted waters, are an invasive species in the UK and an increase in numbers has the potential to disrupt ecosystems, as they can outcompete native species.

Dr Dannielle Green, Senior Lecturer in Biology at Anglia Ruskin University (ARU), said: "Many of the microplastics found in our rivers and oceans have taken years to form, as larger pieces of plastic are broken down over time, However, glitter is a ready-made microplastic that is commonly found in our homes and, particularly through cosmetics, is washed off in our sinks and into the water system.

"Our study is the first to look at the effects of glitter in a freshwater environment and we found that both conventional and alternative glitters can have a serious ecological impact on aquatic ecosystems within a short period of time.

"All types, including so-called biodegradable glitter, have a negative effect on important primary producers which are the base of the food web, while glitter with a biodegradable cellulose core has an additional impact of encouraging the growth of an invasive species.

Read more at Science Daily

World-first system forecasts warming of lakes globally

A groundbreaking study will enable scientists to better predict future warming of the world's lakes due to climate change, and the potential threat to cold-water species such as salmon and trout.

Pioneering research led by the UK Centre for Ecology & Hydrology (UKCEH) has devised the first system that classifies lakes globally, placing each of them in one of nine 'thermal regions' (see map).

Lakes are grouped depending on their seasonal patterns of surface water temperatures, with the coldest thermal region including lakes in Alaska, Canada, northern Russia and China, and the warmest covering lakes in equatorial South America, Africa, India and south-east Asia.

By incorporating climate change models, the scientists predict that by the year 2100, for the most extreme climate change scenario, average lake temperature will be around 4 degrees Celsius warmer and that 66 per cent of lakes globally will be classified in a warmer thermal region than they are now.

The study -- carried out by UKCEH, the Universities of Dundee, Glasgow, Reading and Stirling, plus the Dundalk Institute of Technology -- was funded by the Natural Environment Research Council (NERC) and has been published in the journal Nature Communications.

Professor Stephen Maberly of UKCEH, lead author of the study, explains: "Thanks to cutting-edge analysis using satellite images of more than 700 lakes, taken twice a month over 16 years, we produced the first global lake temperature classification scheme. By combining this with a lake model and climate change scenarios we were able to identify that northern lakes, such as those in the UK, will be particularly sensitive to climate change."

Even relatively small changes in temperature can have a significant negative impact on aquatic wildlife, affecting the speed at which organisms grow and feed, and when they reproduce. As species do not react in the same way, prey and predators have increasingly different breeding and feeding cycles, reducing the amount of potential food available.

Warming also increases the risk of harmful algal blooms, which can have a negative impact on aquatic plants and fish.

Professor Maberly says: "Cold-water fish species in particular can be stressed by warmer temperatures. The potential negative impact on salmonids such as salmon, trout and Arctic charr, for example, is concerning because they play a central ecological role within food webs and also have great economic importance."

The research is aimed at scientists interested in freshwater ecology, climate change, greenhouse gas emissions and biogeochemical cycles.

Professor Andrew Tyler of the University of Stirling, who led the overall project, GloboLakes, says: "This is an example of pioneering UK-led research that has delivered the capability to monitor our inland waters at the global scale from satellite based platforms.

Read more at Science Daily

Almost alien: Antarctic subglacial lakes are cold, dark and full of secrets

Antarctica map

More than half of the planet's fresh water is in Antarctica. While most of it is frozen in the ice sheets, underneath the ice pools and streams of water flow into one another and into the Southern Ocean surrounding the continent. Understanding the movement of this water, and what is dissolved in it as solutes, reveals how carbon and nutrients from the land may support life in the coastal ocean.

Gathering data on the biogeochemistry of these systems is an undertaking of Antarctic proportions. Trista Vick-Majors, Assistant Professor of Biological Sciences at Michigan Technological University, is part of a team that gathered samples from the Whillans Subglacial Lake in West Antarctica and is lead author on a paper about the lake, recently published in Global Biogeochemical Cycles.

"Life is tough -- it can handle a lot," Vick-Majors said. "This paper is putting together what we know about the biology and how active it is under Antarctic ice with information about the composition of organic carbon in the lake."

Life beneath the ice puts up with a lot -- there is no sunlight and pressure from the ice above in combination with heat radiating up from the Earth's core is what melts the water to form the lake, so the temperature hovers just below freezing. Organic carbon, an important food source for microorganisms, is present in relatively high concentrations in Whillans Subglacial Lake, even if it lacks the verdant mess of a Midwest pond in late August. Instead, as cameras dropped down the borehole of Mercer Subglacial Lake (a neighbor of Whillans) reveal, the subglacial lake is dark, cold, full of soft and fluffy sediment, and lined with bubble-filled ice.

The lake bed looks more alien than earth, and studying extreme environments like this does provide insight into what extraterrestrial life could be like or how earthly life might survive in similar conditions. Not that humans, penguins or fish could handle it; life in the waters beneath Antarctica's ice is mostly microbial. They still show signs of life -- organic carbon and other chemical byproducts of living, eating, excreting and dying -- that Vick-Majors and her team can measure and budget.

Using mass balance calculations, the team's research shows that a pool of dissolved organic carbon in the Whillans Subglacial Lake can be produced in 4.8 to 11.9 years. As the lake fills and drains, which takes about the same amount of time, all those nutrients slip and slide their way to the ice-covered coast of the Southern Ocean. Based on the team's calculations, the subglacial lakes in the region provide 5,400% more organic carbon than what microbial life in the ice-covered ocean downstream needs to survive.

"There's no photosynthesis under the ice in the ocean downstream of this lake -- this limits the available food and energy sources in a way that you wouldn't find in a surface lake or the open ocean," Vick-Majors said. "The idea is that these subglacial lakes that are upstream could provide important sources of energy and nutrients for things living in the ice-covered regions of the Southern Ocean."

While the Whillans Subglacial Lake on its own indicates that upstream nutrients may be an important factor, it is only a single source of data in an ice-covered complex of underground lakes, streams and estuary-like mixing zones that undergo seasonal and sporadic fluxes.

To expand their view, Vick-Majors and the rest of the team have been gathering data at other sites (Mercer Subglacial Lake was sampled by the SALSA team in early 2019), and doing so is no small feat. They make it happen with a hot water drill, a specially designed hose, a 10-liter water sampling bottle, some sediment coring devices, and a week of summery polar weather that can plunge to 20 below. The crew wears Tyvek suits and all equipment is thoroughly cleaned. They also filter the drilling water, run it past several banks of ultra-violet lights to knock down microbial contamination, and then heat it up to use the hot water to open an approximately 1000-meter borehole down to the lake.

"Some of that melted ice water, which has now circulated through the drill, is removed from the hole so that when the lake is punctured, water from the lake moves up into the borehole," Vick-Majors said, explaining that the crew has to keep the hot water from the drill separate from the lake water to keep their samples and the lake clean. "It takes about 24 hours to drill the borehole and we keep it open for a few days; gathering a single sample or letting down the cameras can take two hours or more, depending on the equipment."

And the hole keeps trying to refreeze. Plus, Vick-Majors is not a lone scientist; she is embedded in an interdisciplinary team and everyone needs access to the borehole for different experiments. But for all the tight logistics and cold toes, she says it's worth it.

"There is water and there is life under the ice," Vick-Majors said. "These can teach us a lot about our planet because this is a great place to look at somewhat simplified ecosystems, without higher levels of organisms. So we can answer questions about life that can be really hard to answer in other places."

Read more at Science Daily

Mars once had salt lakes similar to those on Earth

Salt flat in Bolivia.

Mars once had salt lakes that are similar to those on Earth and has gone through wet and dry periods, according to an international team of scientists that includes a Texas A&M University College of Geosciences researcher.

Marion Nachon, a postdoctoral research associate in the Department of Geology and Geophysics at Texas A&M, and colleagues have had their work published in the current issue of Nature Geoscience.

The team examined Mars' geological terrains from Gale Crater, an immense 95-mile-wide rocky basin that is being explored with the NASA Curiosity rover since 2012 as part of the MSL (Mars Science Laboratory) mission.

The results show that the lake that was present in Gale Crater over 3 billion years ago underwent a drying episode, potentially linked to the global drying of Mars.

Gale Crater formed about 3.6 billion years ago when a meteor hit Mars and created its large impact crater.

"Since then, its geological terrains have recorded the history of Mars, and studies have shown Gale Crater reveals signs that liquid water was present over its history, which is a key ingredient of microbial life as we know it," Nachon said. "During these drying periods, salt ponds eventually formed. It is difficult to say exactly how large these ponds were, but the lake in Gale Crater was present for long periods of time -- from at least hundreds of years to perhaps tens of thousands of years," Nachon said.

So what happened to these salt lakes?

Nachon said that Mars probably became dryer over time, and the planet lost its planetary magnetic field, which left the atmosphere exposed to be stripped by solar wind and radiation over millions of years.

"With an atmosphere becoming thinner, the pressure at the surface became lesser, and the conditions for liquid water to be stable at the surface were not fulfilled anymore," Nachon said. "So liquid water became unsustainable and evaporated."

The salt ponds on Mars are believed to be similar to some found on Earth, especially those in a region called Altiplano, which is near the Bolivia-Peru border.

Nachon said the Altiplano is an arid, high-altitude plateau where rivers and streams from mountain ranges "do not flow to the sea but lead to closed basins, similar to what used to happen at Gale Crater on Mars," she said. "This hydrology creates lakes with water levels heavily influenced by climate. During the arid periods Altiplano lakes become shallow due to evaporation, and some even dry up entirely. The fact that the Atliplano is mostly vegetation free makes the region look even more like Mars," she said."

Nachon added that the study shows that the ancient lake in Gale Crater underwent at least one episode of drying before "recovering." It's also possible that the lake was segmented into separate ponds, where some of the ponds could have undergone more evaporation.

Because up to now only one location along the rover's path shows such a drying history, Nachon said it might give clues about how many drying episodes the lake underwent before Mars's climate became as dry as it is currently.

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