GET WET!

Mountain spring water is often touted as the cleanest water you can drink. But a new study from the University of Georgia revealed this isn’t the case.

Using data collected over 40 years, researchers detailed how water quality in high-elevation streams has been negatively affected by a combination of historical events and modern changes, namely sediment from rural roads and agricultural runoff.

Unpaved roads are just one of several factors contributing to sediment runoff, said Rhett Jackson, a professor at UGA’s Warnell School of Forestry and Natural Resources and the paper’s lead author.

The paper was published earlier this month in the journal Bioscience.

“We had access to studies from 1976 to last year that encompassed both stream and terrestrial studies,” said Jackson, who worked with researchers from Virginia Tech, the University of Illinois, the University of Minnesota and the U.S. Forest Service to analyze streams in a mountainous portion of North Carolina adjacent to the Coweeta Long-Term Ecological Research Site.

When streams carry a lot of sediment, it makes it more difficult for animals to see food in the water, and it affects fish growth and disease resistance. Sediment also continues to flow downstream and into public water supplies, where it costs cities and towns more to filter.

“Some streams in Macon County have very high sediment concentrations, four times greater than found in forested streams,” added Jackson.

The cost of a view

It’s important to note that Appalachian water quality issues began more than 100 years ago, said Jackson, when European settlers fundamentally changed the balance of the land long inhabited by Native Americans.

“The landscape you see now isn’t what it was like in 1900—the early settlers logged everything,” said Jackson. For generations, native Cherokee Indians farmed the valleys of the Southern Appalachians and left the hillsides forested, for hunting and gathering. But the new settlers cut the forests and even tried to farm the hills, causing erosion and sediment to move into the streams. Today, stream beds continue to show evidence of sediment deposited more than a century ago, even as new sediment pushes through the waters.

Many years later, a new kind of development in the region created a different kind of land disturbance. For generations, residents considered the steep mountain slopes undevelopable. But the 1980s and ’90s brought a desire for mountain getaway homes with views.

By building homes on mountain ridges, he said, it created more land disturbance through carving out unpaved roads and cutting into hillsides, sometimes creating landslides.

“Roadside ditches and unpaved roads produce a lot of sediment, and their sediment production increases as roads get steeper and as gravel roads get more use,” said Jackson.

A typical southern Appalachian forest stream contains sediment amounts—calculated as total suspended solid concentration—of about 8 to 10 milligrams per liter. But in areas with both mountain and valley development, the researchers found sediment concentrations four to six times higher.

Agricultural issues

Farming also takes its toll. The studies researchers analyzed found many streams in the area to have high nutrient concentrations—particularly nitrate. When a stream flowing through a pasture loses its buffer of trees, it loses a natural protection against nutrient runoff.

Streams without shade also have higher water temperatures. In Appalachia, where mountain trout and other wildlife thrive in cold waters, even a few extra degrees in the summer can kill trout or reduce their competitiveness against warm water fish.

Jackson said about 40% of streams in the study area aren’t buffered. But through best-management practices and state and federal programs, landowners can find assistance and resources to reverse the damage. “On small streams, the actions of individual landowners matter a lot,” he said. “Sometimes, we see unusual streamside activities with substantial water quality effects.” For example, researchers found instances of streams diverted through animal enclosures or illicit discharge pipes without clear sources.

Even small steps, such as buffering runoff from a gravel road or planting trees near an open stream, can go a long way, Jackson said.

“Because the water in streams comes from the whole landscape, everything we see on the land has some effect on streams,” he said. “But streams are resilient, and as long as we intelligently modify our actions a little bit, we can farm and live near streams while protecting their water quality. Maintaining the quality of our landscape requires a little thought and work on our parts.”

Scientists have recently confirmed that the world’s lakes are rapidly losing oxygen. With a seven-year, whole-ecosystem study, a team of freshwater scientists at Virginia Tech has been one of the first to take the next step in asking: What does it mean for water quality that oxygen is declining globally?Sticky with sediment, the bottom waters of lakes are more than their deepest, darkest layer. They bury massive portions of the carbon, nitrogen, and phosphorus found in runoff rolling in from the land. As one of nature’s critical nutrient sinks, lakes earn their recognition as “sentinels” of their surroundings, said freshwater scientist Cayelan Carey.

“We think of lakes as sentinels because they truly integrate all of the changes that happen on land,” said Carey, an associate professor of biological sciences in the Virginia Tech College of Science and an affiliated scientist with the Fralin Life Sciences Institute. “Lakes do this really great job of receiving and processing all of this carbon, nitrogen, and phosphorus, preventing them from going downstream and reaching the ocean.”

But that work could be dismantled by anoxia, the loss of oxygenavailability, Carey’s team found in a study published this week in Global Change Biology. Dreaded by scientists for years and recently confirmed as widespread by data from hundreds of lakes, anoxia is sucking oxygen from the world’s fresh waters.

It’s a phenomenon linked to the warming of waters brought on by climate change and to excess pollutant runoff from land use. Warming waters diminish fresh water’s capacity to hold oxygen, while the breakdown of nutrients in runoff by freshwater microbes gobbles up oxygen.

In a seven-year field experiment that manipulated oxygen levelsin the bottom waters of a nearby reservoir, Carey’s team found that with anoxic conditions came effects they had expected: the sediments release a lot of nutrients and carbon. But they weren’t as prepared for the extent of the changes. They observed the lake going from a sink—which retains more nutrients and carbon than it exports—to a source of nutrients downstream, starting a cycle in which anoxia in one lake could beget anoxia in another.

“I had no expectation that there would be this much change in water chemistry,” Carey said. “And to see it consistently and to see it over the seven years of the study—the effect of anoxia was multiple orders of magnitude greater than what I originally predicted.”

FOR MORE INFORMATION: https://phys.org/news/2022-05-vicious-oxygen-loss-threatens-quality.html

ST. PETERSBURG, Fla. (AP) — More than 80 rescued Florida manatees are in rehabilitation centers across the U.S. as wildlife officials try to stem starvation deaths by the marine mammals because of poor water quality.

The latest numbers were released Wednesday by the Florida Fish and Wildlife Conservation Commission and U.S. Fish and Wildlife Service as part of an unprecedented effort to feed starving manatees and treat those in distress.

The state has provided about $1.2 million for the treatment effort, officials said, with the rest of the increasing costs borne by facilities such as the SeaWorld rescue program in Orlando. There are 13 such locations at aquariums and other facilities in Florida, Texas, Ohio, Puerto Rico and elsewhere.

“It’s a huge effort and they do a fantastic job,” said Terri Calleson of the U.S. Fish and Wildlife Service. “A lot of it is happening on their dime.”

Last year, more than 1,100 manatee deaths were recorded largely due to starvation, well above the typical five-year average of about 625 deaths. In 2022 through last week, 326 manatee deaths have been listed, only seven from collisions with boats, according to state wildlife commission statistics.

The experimental feeding program using romaine lettuce continues seven days a week at a Florida Power & Light plant in Brevard County along the east coast where hundreds of manatees typically gather in cold months in the plant’s warm water discharge area.

As of Tuesday, more than 63,000 pounds (28,500 kilograms) of lettuce has been provided to the manatees, said Jon Wallace of the U.S. Fish and Wildlife Service. The food is paid for mostly by donations to the non-profit Fish & Wildife Foundation of Florida.

“That is all still going very well,” Wallace said.

There are an estimated 8,800 or so manatees in Florida waters. That’s a big improvement from the roughly 2,000 animals in the 1990s, part of the reason they were delisted from endangered to threatened by the federal government.

Officials say it’s important for people in Florida’s coastal areas to report any sick or distressed manatees they see so they can be brought to a rehabilitation center.

“Overall, we view these rescue efforts as successful. This is a small victory for us,” said Andy Garrett, manatee rescue coordinator for the state wildlife commission.

But officials also stressed the approach of warmer weather does not mean the starvation problem is over, especially since some of the slow-moving, round-tailed animals will need extensive treatment.

“This need does not stop with the end of cold weather this year,” said Jon Peterson, rescue operations manager at SeaWorld. “Some of the animals have been here a long time. It does take time.”

FOR MORE INFORMATION: https://apnews.com/article/travel-environment-and-nature-florida-orlando-animals-bcce92347c22878bc36bd239ed55a6d3

As a worsening drought forces millions of Californians to face mandatory water restrictions, one corner of Southern California has largely shielded itself from supply-related woes: San Diego County. 

For Western water planners, the path it took to get there serves either as a blueprint or a cautionary tale.

Over the past three decades, San Diego County diversified its water supply, ramped up conservation and invested in big-ticket water infrastructure including the Western hemisphere’s largest desalination plant, which removes salt and impurities from ocean water. As a result, the water agency that serves 24 water utilities including the city of San Diego says it can avoid cuts until at least 2045, even during dry periods. But that security has come at a cost.

San Diego County’s water is among the most expensive in the country, costing about 26% more at the wholesale level in 2021 than the Metropolitan Water District’s, which serves Los Angeles and surrounding counties. Now, two rural irrigation districts in San Diego County home to large avocado industries want to break away from the regional water supplier, saying they can purchase cheaper water elsewhere. If they succeed, water in San Diego County could grow even more expensive.

“San Diego’s situation is very surprising, very striking,” said Michael Hanemann, an environmental economist at Arizona State University who recently was commissioned to study the region’s water costs for a California agency. “I think this is a harbinger of something that’s going to happen elsewhere in California and elsewhere in the U.S.” 

WHY SO EXPENSIVE

San Diegans didn’t always rest easy during drought. In the 1990s, a severe dry period cut the region’s water supply by 30%. At the time, almost all of its water came from the Metropolitan Water District, the country’s largest water provider. That experience and a tense, dysfunctional relationship — California water experts say — with water officials in Los Angeles spurred San Diego County’s aggressive, decades-long pursuit of water self-sufficiency.

“At that point, our community came together and said, ’We’re not going to be in this situation again. We need to plan for our own reliability,” said Sandy Kerl, general manager of the San Diego County Water Authority. 

So in 2003, the water authority cut a deal to get water from the single largest user of the Colorado River, the Imperial Irrigation District, in Southern California. San Diego County funded repairs to leaky canals belonging to Imperial and signed a historic water transfer deal. Today, it receives about 55% of its total supply from Imperial as part of the deal. 

The water authority also helped farmers use less water. It raised dams to increase storage capacity in reservoirs. It provided rebates to homeowners who ripped out grass lawns for water-efficient alternatives.

In 2012, San Diego County forged a deal to get 10% of its water supply from the Carlsbad Desalination Plant for the next 30 years. The plant produces 50 million gallons of drinkable water — enough for about 400,000 people — every day and is by far the region’s most expensive water source.

FOR MORE INFORMATION: https://apnews.com/article/california-droughts-environment-san-diego-81ab84fafe94a0c5c298ede24fd2f7f1

In southwestern Pennsylvania, eight locks and dams that for decades helped barges move goods along the Allegheny, Monongahela and Ohio rivers will in a few years also generate enough power for 75,000 homes.

Rye Development, a Boston-based hydropower company, is retrofitting the dams with turbines to generate electricity and says the upgraded structures will limit damage to the rivers’ water quality and fish.

The project reflects a recent thawing between the industry and conservation groups, which had long opposed dams that can prevent fish migration, alter water temperatures and cause other environmental problems. As the U.S. pushes to transition to low-carbon energy, Rye is among the companies that sees an opportunity to expand hydropower production at existing dams while working to minimize environmental harms.

The recent compromises between the industry and environmental groups are reflected in President Joe Biden’s infrastructure law, which puts $2.5 billion toward projects including dam removals as well as upgrades at existing structures for hydropower and energy storage.

Hydropower, which uses flowing water to spin turbines connected to generators, is the oldest and second-largest renewable energy source in the U.S. after wind power. In 2020, it accounted for roughly 7% of the electricity generated in the country.

The industry hasn’t received as much federal funding and tax incentives as wind and solar, but sees room for growth. Of the 90,000 dams in the country, about 2,500 produce power. Non-powered dams could produce enough power for 9 to 12 million homes, according to an estimate by the Electric Power Supply Association based on federal data from 2012.

Part of the challenge is that most dams in the U.S. were built more than half a century ago. The risk of dam collapses has fueled demolitions in recent years, with more than 40% of the country’s nearly 2,000 dam removals in the past century happening in the last decade. Some are also torn down largely for environmental reasons. 

Last month, federal regulators moved a step closer to approving what would be the largest dam demolition in U.S. history. Removal of the four hydroelectric dams on the Klamath River near the Oregon-California border would help save the river’s salmon and other fish species that can’t reach breeding habitat because of the structures.

The hydropower industry and conservation groups still clash over dams too. On Maine’s Kennebec River, conservation groups and state environmental agencies are pushing for the removal of four hydropower dams that block endangered Atlantic salmon from reaching key habitat. The dams generate about 5% of the state’s renewable energy.

“It’s very easy for individual river systems to get lost in the message of climate change and the need for renewable energy,” said Shannon Ames, executive director of the Low Impact Hydropower Institute, which grades hydropower dams based on environmental criteria.

With persisting drought affecting hydropower production west of the Mississippi River, the industry has a more direct path to expansion in eastern states. 

In Pennsylvania, Rye consulted with the Low Impact Hydropower Institute early in its process and is among a small number of companies seeking certification from the group. 

To get certified, companies must show their structures meet protections for endangered species, cultural and historic uses of rivers, passage for fish and recreational areas. The group says its environmental standards are often stricter than state or federal guidelines.

On a recently certified dam in West Virginia on the Ohio River, for example, dissolved oxygen levels — an important measure of river water quality — were meeting or exceeding state standards, according to a five-year study. In some states, dams certified by the organization qualify for green-energy programs.

Rye said its dams in Pennsylvania will include structures to support fish migration ,and that it is building a fishing pier since federal regulators require hydropower producers to support recreation on river systems. The retrofits are expected to be operational as early as 2025.

FOR MORE INFORMATION: https://apnews.com/article/biden-business-pennsylvania-environment-environment-7c024d8fd9edfab0e39bbfa82fcae699

The Safe Drinking Water Act defines the term “contaminant” as meaning any physical, chemical, biological, or radiological substance or matter in water. Therefore, the law defines “contaminant” very broadly as being anything other than water molecules. Drinking water may reasonably be expected to contain at least small amounts of some contaminants. Some drinking water contaminants may be harmful if consumed at certain levels in drinking water while others may be harmless. The presence of contaminants does not necessarily indicate that the water poses a health risk.

Only a small number of the universe of contaminants as defined above are listed on the Contaminant Candidate List (CCL). The CCL serves as the first level of evaluation for unregulated drinking water contaminants that may need further investigation of potential health effects and the levels at which they are found in drinking water.

Related Information

Learn about contaminants that are currently regulated

How EPA regulates drinking water contaminants

The following are general categories of drinking water contaminants and examples of each:

• Physical contaminants primarily impact the physical appearance or other physical properties of water. Examples of physical contaminants are sediment or organic material suspended in the water of lakes, rivers and streams from soil erosion.
• Chemical contaminants are elements or compounds. These contaminants may be naturally occurring or man-made. Examples of chemical contaminants include nitrogen, bleach, salts, pesticides, metals, toxins produced by bacteria, and human or animal drugs.
• Biological contaminants are organisms in water. They are also referred to as microbes or microbiological contaminants. Examples of biological or microbial contaminants include bacteria, viruses, protozoa, and parasites.
• Radiological contaminants are chemical elements with an unbalanced number of protons and neutrons resulting in unstable atoms that can emit ionizing radiation. Examples of radiological contaminants include cesium, plutonium and uranium.

FOR MORE INFORMATION: https://www.epa.gov/ccl/types-drinking-water-contaminants

Supercomputer simulates water supply in inter-utility agreement study

Mark Twain is attributed with the quote, “Whisky is for drinking, and water is for fighting over!” But what if cooperation yielded more benefit than just going it alone, when it comes to urban water utilities?

A new study of water supply in the North Carolina Research Triangle found that agreements between water utilities can help mitigate their risks.

The research used supercomputer allocations on the Stampede2 system of the Texas Advanced Computing Center awarded by the Extreme Science and Engineering Discovery Environment (XSEDE), which is funded by the National Science Foundation.

The findings are generalizable to any place where water providers allocate regional water resources among users that face challenges in supply and demand and in affordably financing infrastructure improvements.

“We found that cooperation amongst utilities could be beneficial to both their water supply and financial needs compared to more traditional independent planning and management,” said David Gorelick, a postdoctoral research associate at the University of North Carolina, Chapel Hill. Gorelick is with the Center on Financial Risk in Environmental Systems, Department of Environmental Sciences and Engineering, Gillings School of Global Public Health.

The study was published March 2022 in Water Resources Research, a journal of the American Geophysical Union.

The authors started with a computational model they developed together with regional utilities in North Carolina.

“Their participation gives us a lot of confidence that our results will be used at least to inform their behavior and to help avoid some more significant pitfalls when it comes to making big, long term, hundred-million-dollar financial decisions concerning water infrastructure such as new reservoirs or wastewater treatment plants,” Gorelick said.

The model accurately simulates their risk management and long-term infrastructure planning decisions out until 2060.

“This work is not possible without XSEDE supercomputing resources,” said study co-author David Gold, a PhD candidate in the Department of Civil and Environmental Engineering at Cornell University.

Gold and colleagues evaluated the water supply system of the North Carolina Research Triangle of about two million residents, bounded by Chapel Hill, Durham, and Raleigh, over millions of future states out to 2060. This allowed discovery of water management strategies that are robust to a broad set of future conditions.

“Without supercomputing capabilities, we’re flying blind in terms of how the water supply system reacts to different types of uncertainties, whether it’s population growth or changing climate,” Gold said.

“It’s been expansive for us to be able to use Stampede2,” Gold added. “If we were to try to run these simulations on our desktop, it would take us over 15 years to do all the simulations that we ran using Stampede2 over just the course of a few hours.”

A utility-scale computational model of the region was thus developed, using the WaterPaths stochastic simulation software, a utility planning and management tool. The risk-of-failure was evolved based on reservoir capacity dynamics that change on hydroclimatic conditions, human demands, and management decisions that combine weekly portfolio management with long-term annual infrastructure investments.

Some of the risks of inter-utility agreements include exposure to asymmetric partner growth or the inflexibility of the agreement structure itself to respond to the ups and downs of supply and demand.

Interestingly, the authors hypothesized that more flexible agreements might benefit partners more by allowing them to adapt to changing conditions.

“In fact, we found that utilities experienced more financial risk in these cases,” Gorelick said. The study found that with less flexible agreements, utilities are limited to mitigating their own risks. But when agreements can be updated over time, each utility is more exposed to the risks and the uncertainties of their partners.

“We found that cooperation is a good thing. But the type and the manner in which cooperation occurs can be very important for water utilities, and thus the water rates that all of us pay to get our water bills,” Gorelick said.

A simple example of an agreement studied in the paper was a fixed allocation agreement, such as that for a new reservoir or wastewater treatment plant. Because municipalities and local governments in the U.S. can enact inter-local agreements, utilities can partner together and be allocated fixed allocations of storage or treatment capacity in a shared project at the outset.

If one utility, for instance, pays for 20% of the development of that plant, they are allowed to use 20% of its capacity.

“Why these sorts of agreements matter, and why we wanted to test at least a couple in this study is that the agreements are widespread and very customizable from place to place,” Gorelick said.

Thus far, there have been very few research efforts to assess their performance in terms of utility supply and financial objects.

Said Gold: “Today, our water systems face greater challenges than ever. But, we also have tools that we’ve never had before, in terms of supercomputers. By using resources, such as those available at XSEDE, we are able to level the playing field a bit. When we think about the challenges and uncertainties coming from population growth and changing climate, these computer resources allow us insight into the potential effects of these changes and the support to develop sustainable management strategies that can keep our water supply reliable for years to come.”

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Story Source:

Materials provided by University of Texas at Austin, Texas Advanced Computing Center. Original written by Jorge Salazar. Note: Content may be edited for style and length.

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Journal Reference:

1. David E. Gorelick, David F. Gold, Patrick M. Reed, Gregory W. Characklis. Impact of Inter‐Utility Agreements on Cooperative Regional Water Infrastructure Investment and Management Pathways. Water Resources Research, 2022; 58 (3) DOI: 10.1029/2021WR030700

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Impacts of large-scale afforestation on precipitation reach far beyond country or even continent level

How would afforestation and restoration of large areas worldwide affect water-fluxes world wide? A new study led by Wageningen University researcher Anne Hoek van Dijke with contributions from Martin Herold, GFZ, has interesting answers. Impacts on precipitation reach far beyond country or even continent level: tree restoration in the Amazon can, for example, affect rainfall in Europe and Eastern Asia. The study, published in Nature Geoscience on May 11, 2022, has calculated the global impact of large-scale tree restoration on water fluxes and water availability.

“Restauration and planting more trees is seen as viable solution for enhancing carbon storage and the biodiverse functioning of ecosystems. With innovative data and analysis, our interdisciplinary analysis highlights that the hydrological effects are important for how and where such nature-based solutions are more suitable to achieve towards more climate-smart and sustainable future landscapes,” says Martin Herold from the GFZ German Research Centre for Geosciences, who contributed to the study led by Anne Hoek van Dijke from Wageningen University & Research.

The researchers calculated the hydrological effects of the “global tree restoration potential”: a global map highlighting 900 million hectares where more trees could grow or be planted given local climate conditions, and without encroaching on agricultural and urban land. The increase in evaporation resulting from the increased tree cover was calculated globally at high resolution. The study used data-driven models that describe how much rainfall evaporates, and how much goes to streamflow. Anne Hoek van Dijke, PhD candidate Hydrology and Remote Sensing at Wageningen University & Research: “These models include a vegetation parameter for forest and non-forest conditions that was calibrated to a range of different evaporation and streamflow measurements. Afterwards, we calculated where, and to what extent, the increased evaporation would return to the land surface as increased precipitation.”

Local and global shifts in water availability

The results show that large-scale tree restoration can locally increase evaporation annually by nearly 10 litres on average for every square meter of restored forest. Locally, in the tropics particularly, this effect can be much larger, with almost 250 litres for every square meter. Crucially, not all of this water returns to the land surface. Only around 70% of the extra water in the atmosphere returns to the land, while the remaining 30% is shed over the oceans through rain. On a global scale, this means that tree restoration results in a net decrease in water availability.

For individual river basins, the impact of tree restoration is more complex. Following tree restoration, streamflow for major river basins would generally decrease (by up to around 10%). But for other river basins (e.g. the Yangtze and Amazon river), streamflow reduction will be close to zero because the negative impact of enhanced evaporation is compensated by increased rainfall due to forests in these areas. Interestingly, some of these basins possibly will even gain water.

The study presents the results under current climate conditions. Under a warmer climate, the tree restoration potential would decrease. Also, future climate change could increase evaporation and annual precipitation, which will affect global atmospheric circulation patterns.

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Story Source:

Materials provided by GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre. Note: Content may be edited for style and length.

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Journal Reference:

1. Anne J. Hoek van Dijke, Martin Herold, Kaniska Mallick, Imme Benedict, Miriam Machwitz, Martin Schlerf, Agnes Pranindita, Jolanda J. E. Theeuwen, Jean-François Bastin, Adriaan J. Teuling. Shifts in regional water availability due to global tree restoration. Nature Geoscience, 2022; 15 (5): 363 DOI: 10.1038/s41561-022-00935-0

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GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre. “How does forest restoration affect water cycles? Impacts of large-scale afforestation on precipitation reach far beyond country or even continent level.” ScienceDaily. ScienceDaily, 11 May 2022. <www.sciencedaily.com/releases/2022/05/220511123516.htm>.

FOR MORE INFORMATION: https://www.sciencedaily.com/releases/2022/05/220511123516.htm

Study shows unexpected negative impact by CO2 on important plankton group

Diatoms are the most important producers of plant biomass in the ocean and help to transport carbon dioxide (CO₂) from the atmosphere into the deep ocean and thus regulate our climate. Because diatoms rely on silica rather than calcium carbonate to build their shells, they were previously thought to benefit from ocean acidification — a chemical change in seawater triggered by the increasing uptake of CO2 that makes calcification more difficult. In a study published today in Nature, scientists at GEOMAR Helmholtz Centre for Ocean Research Kiel show that diatoms, which are a type of plankton, are also affected. Analyses of data from field experiments and model simulations suggest that ocean acidification could drastically reduce diatom populations.

While calcifying organisms like oysters and corals have difficulty forming their shells and skeletons in more acidic seawater, diatoms have been considered less susceptible to the effects of ocean acidification — a chemical change triggered by the uptake of carbon dioxide (CO2). The globally widespread tiny diatoms use silica, a compound of silicon, oxygen and hydrogen, as a building material for their shells. That diatoms are nevertheless under threat has now been demonstrated for the first time by researchers from GEOMAR Helmholtz Centre for Ocean Research Kiel, the Institute of Geological and Nuclear Sciences Limited New Zealand and the University of Tasmania in a study published in Nature. For the study, researchers linked an overarching analysis of various data sources with Earth system modeling. The findings provide a new assessment of the global impact of ocean acidification.

As a result of ocean acidification, the silicon shells of diatoms dissolve more slowly. This is not an advantage — it causes diatoms to sink into deeper water layers, before they chemically dissolve and are converted back into silica. Consequently, this nutrient is more efficiently exported to the deep ocean and thus becomes scarcer in the light-flooded surface layer, where it is needed to form new shells. This causes a decline in diatoms, according to the scientists in their recent publication. Diatoms contribute 40 percent of the production of plant biomass in the ocean and are the basis of many marine food webs. They are also the main driver of the biological carbon pump that transports CO₂ into the deep ocean for long-term storage.

Dr. Jan Taucher, marine biologist at GEOMAR and first author of the study says: “With an overarching analysis of field experiments and observational data, we wanted to find out how ocean acidification affects diatoms on a global scale. Our current understanding of ecological effects of ocean change is largely based on small-scale experiments, that is, from a particular place at a particular time. These findings can be deceptive if the complexity of the Earth system is not taken into account. Our study uses diatoms as an example to show how small-scale effects can lead to ocean-wide changes with unforeseen and far-reaching consequences for marine ecosystems and matter cycles. Since diatoms are one of the most important plankton groups in the ocean, their decline could lead to a significant shift in the marine food web or even a change for the ocean as a carbon sink.”

The meta-analysis examined data from five mesocosm studies from 2010 to 2014, from different ocean regions ranging from Arctic to subtropical waters. Mesocosms are a type of large-volume, oversized test tube in the ocean with a capacity of tens of thousands of liters, in which changes in environmental conditions can be studied in a closed but otherwise natural ecosystem. For this purpose, the water enclosed in the mesocosms was enriched in carbon dioxide to correspond to future scenarios with moderate to high increases in atmospheric CO₂ levels. For the present study, the chemical composition of organic material from sediment traps was evaluated as it sank through the water contained in the experimental containers over the course of several weeks of experiments. Combined with measurements from the water column, an accurate picture of biogeochemical processes within the ecosystem emerged.

The findings obtained from the mesocosm studies could be confirmed using global observational data from the open ocean. They show — in line with the results of the meta-analysis — a lower dissolution of the silicon shells at higher seawater acidity. With the resulting data sets, simulations were performed in an Earth system model to assess the ocean-wide consequences of the observed trends.

“Already by the end of this century, we expect a loss of up to ten percent of diatoms. That’s immense when you consider how important they are to life in the ocean and to the climate system,” Dr. Taucher continued. “However, it is important to think beyond 2100. Climate change will not stop abruptly, and global effects in particular take some time to become clearly visible. Depending on the amount of emissions, our model in the study predicts a loss of up to 27 percent silica in surface waters and an ocean-wide decline in diatoms of up to 26 percent by the year 2200 — more than a quarter of the current population.”

This finding of the study is in sharp contrast to the previous state of ocean research, which sees calcifying organisms as losers and diatoms being less affected by ocean acidification. Professor Ulf Riebesell, marine biologist at GEOMAR and head of the mesocosm experiments adds: “This study once again highlights the complexity of the Earth system and the associated difficulty in predicting the consequences of human-made climate change in its entirety. Surprises of this kind remind us again and again of the incalculable risks we run if we do not counteract climate change swiftly and decisively.”

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Story Source:

Materials provided by Helmholtz Centre for Ocean Research Kiel (GEOMAR). Note: Content may be edited for style and length.

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Journal Reference:

1. Jan Taucher, Lennart T. Bach, A. E. Friederike Prowe, Tim Boxhammer, Karin Kvale, Ulf Riebesell. Enhanced silica export in a future ocean triggers global diatom decline. Nature, 2022; 605 (7911): 696 DOI: 10.1038/s41586-022-04687-0

FOR MORE INFORMATION: https://www.sciencedaily.com/releases/2022/05/220525182619.htm

Engineers at UC Riverside are the first to report selective breakdown of a particularly stubborn class of PFAS called fluorinated carboxylic acids (FCAs) by common microorganisms.

Under anaerobic conditions, a carbon-carbon double bond is crucial for the shattering the ultra-strong carbon-fluorine bond by microbial communities. While breaking the carbon-carbon bond does not completely degrade the molecule, the resulting products could be relayed to other microorganisms for defluorination under in aerobic conditions.

The achievement builds upon prior work by the same researchers, who were the first to report successful microbial defluorination of a fully fluorinated PFAS structure by replacing carbon-fluorine bonds with carbon-hydrogen bonds.

Per- and polyfluoroalkyl substances, or PFAS, are a group of over 9,000 chemicals used in countless industrial processes and commercial products since the 1940s. As a result, PFAS have found their way into the water cycle and are now found in virtually every water source. These chemicals contain a bond between fluorine and carbon atoms that is the strongest single bond known, rendering PFAS non-biodegradable and resistant to conventional water treatment methods. They wind up in the tissues of organisms, including humans, where they have been associated with some types of cancer, thyroid and liver problems, and likely other, still poorly understood, health problems.

In an earlier paper, Yujie Men, an assistant professor of chemical and environmental engineering, and her colleagues reported using anaerobic microbial communities often used for dechlorination to degrade two specific PFAS, including one fully fluorinated, or perfluorinated, structure.

The new paper takes this research a step further by showing that the point of entry for the anaerobic microbes was a double bond between carbon atoms located next to the carboxyl group of the FCA molecules. Trifluoromethyl branches on the double bond could further enhance the biodegradability.

Microbes capable of doing this type of defluorination are not rare. Using activated sludge — microbial communities commonly used in wastewater treatment facilities to break down and remove organic matter — and an anaerobic condition, the researchers successfully repeated their earlier experiment with more structurally similar PFAS.

“Currently biocatalysts that can do defluorination of perfluorinated compounds like PFOA are very rare. We still know very little about which microbes or enzymes can do the defluorination of PFAS in general and how,” said Men. “Our work is at the leading edge of finding this information.”

Even when scientists figure out ways to break the initial carbon-fluorine bond in perfluorinated compounds, their work isn’t done because the molecules are likely broken down into other molecules that could also be harmful. Successful remediation of PFAS-contaminated environments requires initial breakdown of the PFAS parent molecule followed by complete degradation of the secondary molecules.

One recent study by the Men group demonstrated that activated sludge communities were able to completely degrade the secondary molecule from chemical degradation of one type of perfluorinated chemical via a process known as cometabolism. Their new study further implies that simply through the cooperation among different microbial groups, such as anaerobic and aerobic bacteria, deeper defluorination could also be achieved for certain perfluorinated chemicals.

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Story Source:

Materials provided by University of California – Riverside. Original written by Holly Ober. Note: Content may be edited for style and length.

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Journal Reference:

1. Yaochun Yu, Shun Che, Changxu Ren, Bosen Jin, Zhenyu Tian, Jinyong Liu, Yujie Men. Microbial Defluorination of Unsaturated Per- and Polyfluorinated Carboxylic Acids under Anaerobic and Aerobic Conditions: A Structure Specificity Study. Environmental Science & Technology, 2022; 56 (8): 4894 DOI: 10.1021/acs.est.1c05509

FOR MORE INFORMATION: https://www.sciencedaily.com/releases/2022/05/220523162819.htm