It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Friday, October 04, 2024
Oyster reefs once thrived along Europe’s coasts – now they’re gone
Oysters once formed extensive reefs along much of Europe's coastline – but these complex ecosystems were destroyed over a century ago, new research shows.
Based on documents from the 18th and 19th Centuries, the study reveals that European flat oysters formed large reefs of both living and dead shells, providing a habitat supporting rich biodiversity.
Today these oysters are mostly found as scattered individuals – but the researchers found evidence of reefs almost everywhere, from Norway to the Mediterranean, covering at least 1.7 million hectares, an area larger than Northern Ireland.
The research was led by the University of Exeter and The University of Edinburgh.
Native oyster reefs created their own ecosystems, full of a diverse range of underwater life – supporting a greater number of species than surrounding areas.
In addition to creating homes for the almost 200 recorded fish and crustacean species, the oysters also played a vital role in stabilising shorelines, nutrient cycling and water filtration – with a single adult oyster filtering up to 200 litres of water a day.
Restoration projects are under way across Europe – and small-scale habitat restoration, such as The Wild Oyster Project, led by ZSL and partners, are key stepping stones to the return of these vital ecosystems on an international scale.
However, restoration efforts need to be scaled up with support from governments and other decision makers across the continent.
“Human activities have affected the ocean for centuries,” said Dr Ruth Thurstan, from the University of Exeter and part of the Convex Seascape Survey, an ambitious five-year project examining ocean carbon storage.
“This makes it difficult to discover what our marine ecosystems used to look like, which in turn hampers conservation and recovery.
“Few people in the UK today will have seen a flat oyster, which is our native species. Oysters still exist in these waters but they’re scattered, and the reefs they built are gone.
“We tend to think of our seafloor as a flat, muddy expanse, but in the past many locations were a three-dimensional landscape of complex living reefs – now completely lost from our collective memory.”
Due to their economic and cultural significance, oysters feature in historical records including newspapers, books, travel writing, landing records, nautical charts, early scientific investigations and interviews with fishermen.
“By combining descriptive accounts from a range of historical sources, we can build a picture of our past seas,” said Dr Thurstan, who is mapping past ocean changes as part of the Convex Seascape Survey.
“The greatest concentration of oyster reefs we found was in the North Sea.”
Records show extensive reefs existed along the coasts of modern France, Denmark, Germany, the Netherlands, the Republic of Ireland and the UK.
“Oyster reefs are slow to develop, with layers of new oysters building up on the dead shells of their predecessors, but their destruction through overfishing was relatively rapid,” said Dr Philine zu Ermgassen, honorary researcher at the University of Edinburgh.
“This has caused a fundamental restructuring and ‘flattening’ of our seafloors – removing thriving ecosystems and leaving an expanse of soft sediment behind.
“Thanks to this historical ecology research, we are now able to quantitatively describe what oyster reefs looked like before they were impacted, and the spatial extent of the ecosystems they formed.
“These were huge areas that were thickly crusted with oysters and crawling with other marine life.”
The research team was made up of more than 30 European researchers from the Native Oyster Restoration Alliance.
The study was partly funded by the European Research Council.
The paper, published in the journal Nature Sustainability, is entitled: “Records reveal the vast historical extent of European oyster reef ecosystems.”
Oyster reefs have largely disappeared, but clumps of oysters can still be found
Credit
Stephane Pouvreau / Ifremer
Whitstable, Kent 1) Boats Going Out 2) Dredge 3) Oyster Bags 4) Dredging 5) Landing Oysters (IMAGE)
University of Exeter
Whitstable, Kent 1) Boats Going Out 2) Dredge 3) Oyster Bags 4) Dredging 5) Landing Oysters. From the Illustrated London News
Records reveal the vast historical extent of European oyster reef ecosystems
Article Publication Date
3-Oct-2024
Decades-long research reveals new understanding of how climate change may impact caches of Arctic soil carbon
Colorado State University
Utilizing one of the longest-running ecosystem experiments in the Arctic, a Colorado State University-led team of researchers have developed a better understanding of the interplay among plants, microbes and soil nutrients — findings that offer new insight into how critical carbon deposits may be released from thawing Arctic permafrost.
Estimates suggest that Arctic soils contain nearly twice the amount of carbon that is currently in the atmosphere. As climate change has caused portions of Earth’s northernmost polar regions to thaw, scientists have long been concerned about significant amounts of carbon being released in the form of greenhouse gases, a process fueled by microbes.
Much of the efforts to study and model this scenario have focused specifically on how rising global temperatures will disrupt the carbon currently locked in Arctic soils. But warming is impacting the region in other ways, too, including changing plant productivity, the overall composition of vegetation across the landscape, and the balance of nutrients in the soil. These changes in plant composition will also affect the way carbon is cycled from the soil into the atmosphere, according to a study published this week in the journal Nature Climate Change. The work was led by Megan Machmuller, a research scientist in CSU’s Soil and Crop Sciences Department.
“Our work focused on pinpointing the mechanisms that are responsible for controlling the fate of carbon in the Arctic,” Machmuller said. “We know temperature plays a large role, but there are also ecosystem shifts that are co-occurring with climate change in this region.”
In particular, Machmuller said, the region is experiencing a kind of “shrub-ification” — an increase in shrub abundance and growth. And what Machmuller and her co-authors found is that over long periods those shrubs may contribute to keeping more carbon in the ground.
“There’s been a lot of focus on the direct effects of warming on soil carbon,” said co-author Laurel Lynch, assistant professor at the University of Idaho, “but what we’re finding with this work is that it’s more complex. We need to think about this ecosystem as a whole community with many interacting parts and competing mechanisms.”
A surprising finding
For the new work, Machmuller and team tested soil samples from a 35-year ecosystem experiment in the Arctic. In 1981, scientists began adding nutrients to test plots at the Arctic Long-Term Ecological Research site in northern Alaska, situated near Toolik Lake at the base of the Brooks Mountain Range. The original idea was to understand how Arctic vegetation would respond to additional nutrients over time, but the experiment has also allowed scientists to examine how long-term changes to the soil can impact carbon storage.
After 20 years, scientists found that there had been a significant loss of soil carbon when nutrients were added compared to the control plots, an important finding that shaped broad scientific understanding of how the Arctic might respond to climate change. Those experiments continued, and Machmuller and her team tested the plots again after 35 years of continuous nutrient application.
Instead of continued carbon loss, however, they found that the trend had reversed. After 35 years, the amount of carbon stored in the test plots had either recovered or exceeded the amount in the nearby control plots. “We were really surprised by these results and became curious about the underlying mechanism,” Machmuller said.
Machmuller and her team ran advanced isotope tracing experiments in the lab to learn more about how carbon was moving through the system. What they found was that when the nutrients were first added, they stimulated microbial decomposition — a natural process that involves microbes churning through organic matter in the soil that results in the release of carbon dioxide.
But that changed over time, as nutrients were continuously added to the test plots. “Shrubs conditioned the soil in a way that shifted microbial metabolism, slowing rates of decomposition and allowing soil carbon stocks to rebuild,” Lynch said. “We didn’t expect that.”
“This offers a potential biological mechanism that might explain why we observed a net loss of carbon in the first 20 years but not after 35,” Machmuller said.
The importance of looking long-term
These results, Machmuller said, demonstrate that how the Arctic might respond to climate change is more complicated than previously thought. “It’s a complex puzzle,” she said, “and this study has emphasized for us the importance of using long-term studies to advance our understanding of ecosystem processes.”
Gus Shaver, a researcher scientist who helped set up the initial Toolik Lake experimental plots in 1981 and is a co-author on the study, also stressed the value of doing this kind of work over longer periods of time. “We’ve shown that long-term experiments offer frequent surprises as we follow the trajectory of their responses over time,” Shaver said. “What you find in the first few years of an experiment is often not what you learn from the 10th or 15th or 35th year.”
Lynch noted that as this ecosystem changes, there are other factors to consider beyond just carbon. Although an increase in shrub abundance could keep more soil carbon from transferring into the atmosphere, other impacts are not as beneficial, she said. “When you have one plant species that is massively outcompeting the rest of the community, there are major ecosystem implications,” Lynch said. For example, she said, “habitat and food sources for many animals in the Arctic depend on diverse plant communities, and the loss of this diversity can ripple through the entire ecosystem.”
Lauren Gifford, associate director of CSU’s Soil Carbon Solutions Center, who was not involved with the study, said the work highlights the need for more robust and detailed modeling to better anticipate how climate change will impact the carbon stored in the Arctic. “This is a remarkable 35-year study of one of Earth’s most vulnerable ecosystems,” Gifford said. “Even with comprehensive long-term studies, the impacts of climate change often remain uncertain. Interventions to help adapt to and mitigate climate change may lead to outcomes that are analogous, contradictory, or produce unintended consequences.”
For her part, Machmuller hopes the work will encourage future research on this topic. “Carbon research in the Arctic has been a hot topic for a long time because of the critical role it plays in regulating our global climate,” she said. “But we still don’t have a handle on what exactly the future carbon balance will look like.”
A robot pangolin designed to plant trees is the winner of this year's Natural Robotics Contest. As the winning entry, the pangolin – dubbed "Plantolin" – has been brought to life by engineers at the University of Surrey in the United Kingdom.
Out of 184 entries, the winning design came from Dorothy, a high school student from California.
Dorothy said:
"My entry was inspired by pangolins since they are fascinating creatures and have a very distinct armoured and prehistoric appearance (like a walking pine cone). They're not very fast or ferocious but have an adorable waddle walk.
"In my high school classes, we learned about how deforestation contributes to climate change. The restoration of forests through planting more trees is essential for the sustainable development of our planet.
"Pangolins spend a lot of their time digging in the ground, so I thought a planter robot inspired by the pangolin's behaviour would be very natural."
After Dorothy's design was chosen, a working version was built at the University of Surrey.
Plantolin roves on two wheels, with a long, movable tail for balance. Covered in plywood scales, it digs using its claws, depositing a yew "seed bomb" into the hole.
Dr Rob Siddall, a roboticist at the University of Surrey who built Plantolin, said:
"In the wild, large animals will cut paths through the overgrowth and move seeds. This doesn't happen nearly as much in urban areas like the South East of England – so there's definitely room for a robot to help fill that gap.
"Dorothy's brilliant design reminds us how we can solve some of our biggest challenges by looking to nature for inspiration."
The annual Natural Robotics Contest rewards robot designs inspired by nature. It is funded by the British Ecological Society's outreach grant programme. Last year's winner was Gillbert, a robot fish designed to clean the sea of microplastic.
Its partners include the University of Surrey, Queen Mary University of London, the Royal College of Art, EPFL Lausanne, the Technical University of Munich, and Alexander Humboldt University, Berlin.
Credit: Ludmilla Aristilde/Northwestern University
Researchers have long observed that a common family of environmental bacteria, Comamonadacae, grow on plastics littered throughout urban rivers and wastewater systems. But what, exactly, these Comamonas bacteria are doing has remained a mystery.
Now, Northwestern University-led researchers have discovered how cells of a Comamonas bacterium are breaking down plastic for food. First, they chew the plastic into small pieces, called nanoplastics. Then, they secrete a specialized enzyme that breaks down the plastic even further. Finally, the bacteria use a ring of carbon atoms from the plastic as a food source, the researchers found.
The discovery opens new possibilities for developing bacteria-based engineering solutions to help clean up difficult-to-remove plastic waste, which pollutes drinking water and harms wildlife.
The study will be published on Thursday (Oct. 3) in the journal Environmental Science & Technology.
“We have systematically shown, for the first time, that a wastewater bacterium can take a starting plastic material, deteriorate it, fragment it, break it down and use it as a source of carbon,” said Northwestern’s Ludmilla Aristilde, who led the study. “It is amazing that this bacterium can perform that entire process, and we identified a key enzyme responsible for breaking down the plastic materials. This could be optimized and exploited to help get rid of plastics in the environment.”
The new study builds on previous research from Aristilde’s team, which unraveled the mechanisms that enable Comamonas testosteri to metabolize simple carbons generated from broken down plants and plastics. In the new research, Aristilde and her team again looked to C. testosteroni, which grows on polyethylene terephthalate (PET), a type of plastic commonly used in food packaging and beverage bottles. Because it does not break down easily, PET is a major contributor to plastic pollution.
“It’s important to note that PET plastics represent 12% of total global plastics usage,” Aristilde said. “And it accounts for up to 50% of microplastics in wastewaters.”
Innate ability to degrade plastics
To better understand how C. testosteroni interacts with and feeds on the plastic, Aristilde and her team used multiple theoretical and experimental approaches. First, they took bacterium — isolated from wastewater — and grew it on PET films and pellets. Then, they used advanced microscopy to observe how the surface of the plastic material changed over time. Next, they examined the water around the bacteria, searching for evidence of plastic broken down into smaller nano-sized pieces. And, finally, the researchers looked inside the bacteria to pinpoint tools the bacteria used to help degrade the PET.
“In the presence of the bacterium, the microplastics were broken down into tiny nanoparticles of plastics,” Aristilde said. “We found that the wastewater bacterium has an innate ability to degrade plastic all the way down to monomers, small building blocks which join together to form polymers. These small units are a bioavailable source of carbon that bacteria can use for growth.”
After confirming that C. testosteroni, indeed, can break down plastics, Aristilde next wanted to learn how. Through omics techniques that can measure all enzymes inside the cell, her team discovered one specific enzyme the bacterium expressed when exposed to PET plastics. To further explore this enzyme’s role, Aristilde asked collaborators at Oak Ridge National Laboratory in Tennessee to prepare bacterial cells without the abilities to express the enzyme. Remarkably, without that enzyme, the bacteria’s ability to degrade plastic was lost or significantly diminished.
How plastics change in water
Although Aristilde imagines this discovery potentially could be harnessed for environmental solutions, she also says this new knowledge can help people better understand how plastics evolve in wastewater.
“Wastewater is a huge reservoir of microplastics and nanoplastics,” Aristilde said. “Most people think nanoplastics enter wastewater treatment plants as nanoplastics. But we’re showing that nanoplastics can be formed during wastewater treatment through microbial activity. That’s something we need to pay attention to as our society tries to understand the behavior of plastics throughout its journey from wastewater to receiving rivers and lakes.”
The study, “Mechanisms of polyethylene terephthalate pellet fragmentation into nanoplastics and assimilable carbons by wastewater Comamonas,” was supported by the National Science Foundation (award number CHE-2109097).
Journal
Environmental Science & Technology
Method of Research
Experimental study
Subject of Research
Cells
Article Title
Mechanisms of polyethylene terephthalate pellet fragmentation into nanoplastics and assimilable carbons by wastewater Comamonas
Article Publication Date
3-Oct-2024
Plastic-eating enzyme identified in wastewater microbes
American Chemical Society
Plastic pollution is everywhere, and a good amount of it is composed of polyethylene terephthalate (PET, ♳). This polymer is used to make bottles, containers and even clothing. Now, researchers report in ACS’ Environmental Science & Technology that they have discovered an enzyme that breaks apart PET in a rather unusual place: microbes living in sewage sludge. The enzyme could be used by wastewater treatment plants to break apart microplastic particles and upcycle plastic waste.
Microplastics are becoming increasingly prevalent in places ranging from remote oceans to inside bodies, so it shouldn’t be a surprise that they appear in wastewater as well. However, the particles are so tiny that they can slip through water treatment purification processes and end up in the effluent that is reintroduced to the environment. But effluent also contains microorganisms that like to eat those plastic particles, including Comamonas testosteroni — so named because it degrades sterols like testosterone. Other bacterial species, including the common E. coli,have previously been engineered to turn plastic into other useful molecules. However, C. testosteroni naturally chews up polymers, such as those in laundry detergents, and terephthalate, a monomer building block of PET. So, Ludmilla Aristilde and colleagues wanted to see if C. testosteroni could also produce enzymes that degrade the PET polymer.
The team incubated a strain of C. testosteroni with PET films and pellets. Although the microbes colonized both shapes, microscopy revealed that the microbes preferred the rougher surface of the pellets, breaking them down to a greater degree than the smooth films. To better simulate conditions in wastewater environments, the researchers also added acetate, an ion commonly found in wastewater. When acetate was present, the number of bacterial colonies increased considerably. Though C. testosteroni produced some nano-sized PET particles, it also completely degraded the polymer to its monomers — compounds that C. testosteroni and other environmental microbes can use as a source of carbon to grow and develop, or even convert into other useful molecules, according to the team.
Next, the researchers used protein analysis to identify the key enzyme that gives this microbe its plastic-eating abilities. Though this new enzyme was distinct from previously described PET-busting enzymes based on its overall protein sequence, it did contain a similar binding pocket that was responsible for PET breakdown. When the gene encoding for this key enzyme was placed into a microbe that doesn’t naturally degrade PET, the engineered microbe gained the ability to do so, proving the enzyme’s functionality. The researchers say that this work demonstrates C. testosteroni’s utility for upcycling PET and PET-derived carbons, which could help reduce plastic pollution in wastewater.
The authors acknowledge funding from the U.S. National Science Foundation, the U.S. Department of Energy, the Office of Energy Efficiency and Renewable Energy, the Advanced Materials and Manufacturing Technologies Office, and the Bioenergy Technologies Office as part of the BOTTLE Consortium.
###
The American Chemical Society (ACS) is a nonprofit organization chartered by the U.S. Congress. ACS’ mission is to advance the broader chemistry enterprise and its practitioners for the benefit of Earth and all its people. The Society is a global leader in promoting excellence in science education and providing access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals, scientific conferences, e-books and weekly news periodical Chemical & Engineering News. ACS journals are among the most cited, most trusted and most read within the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate breakthroughs by curating, connecting and analyzing the world’s scientific knowledge. ACS’ main offices are in Washington, D.C., and Columbus, Ohio.
“Mechanisms of Polyethylene Terephthalate Pellet Fragmentation into Nanoplastics and Assimilable Carbons by Wastewater Comamonas”
Article Publication Date
3-Oct-2024
Scientists develop novel method for strengthening PVC products
New method may mean less microplastic pollution
Ohio State University
COLUMBUS, Ohio – Researchers have developed a way to make one type of plastic material more durable and less likely to shed dangerous microplastics.
The study identified a secure way to attach chemical additives to polyvinyl chloride (PVC).
Found in everything from toys, construction supplies and medical packaging, PVC plastics currently rank third among the most used plastics worldwide. Despite its widespread use, pure PVC is brittle and sensitive to heat, and manufacturers can only utilize it after stabilizing its properties with other chemicals.
However, these additives, or plasticizers, are only a short-term fix for stabilizing PVC. Over time, plasticizers leach from the plastics, which allows the material to deteriorate into potentially hazardous organics and microplastics. Now, a team led by Christo Sevov, the principal investigator of the study and an associate professor in chemistry and biochemistry at The Ohio State University, found that using electricity to permanently affix those chemical additives can prevent such unwanted reactions.
“Instead of mixing in those chemicals, our method involves chemically bonding the plasticizer compound directly to PVC by grafting them onto the backbone of the polymer,” said Sevov.
Altering PVC molecules in this way allows for them to become more durable and resistant to chemical changes, eventually leading to materials with more robust properties.
“This is really one of the few examples that we have where there’s this much control over changing the properties of PVC,” said Sevov. “So this is the first step in controllably modifying PVC to give it properties you’re interested in, whether it’s hard, stretchy or soft.”
The team did run into some challenges; synthetic polymer modifications often fail because the reactions were originally developed for small-molecule analogs, not big-molecule analogs such as pure PVC. To solve this, researchers optimized the catalyst they used in their process, and through trial and error, were able to overcome the issues that arise when editing big molecules.
The study was recently published in the journal Chem.
Outside of making leaps in organic chemistry, the team’s work also has implications for the environment, as putting a cap on how quickly plastics degrade can do much to curb the release of microplastics — tiny pieces of plastic debris — into our surroundings.
Today, scientists know that these particles, which have been found to pollute the air, water and our food supply, are harmful both to humans and wildlife. The average person likely ingests between 78,000 and 211,000 of these particles every year.
But as experts are beginning to understand the long-term impact microplastics have on Earth, organic chemists are racing to find ways to phase them out of everyday life, said Sevov.
“Many chemists are shifting their efforts to studying big molecules and developing new chemistries for upcycling, recycling and modifying well-known polymers,” he said. For example, trying to recycle PVC products can cause further degradation to the material due to the high temperatures it takes to convert plastic into something else, so the process isn’t very efficient.
But using Sevov’s method, “You can potentially reuse the material many, many more times before it really begins to fall apart, improving its lifetime and reusability,” he said.
In the future, more control over which materials will be safe for consumers will come once efforts to fix PVC leakage can be reliably scaled up, something that the study emphasizes that, at the moment, is possible with their method alone.
“There’s no better way to do this on the scale you would need for commercial PVC modification because it is an immense process,” said Sevov. “There’s still a lot to play around with before we solve the microplastic situation, though now we’ve laid the groundwork for how to do it.”
Other Ohio State co-authors include Jordan L.S. Zackasee, Valmuri Srivardhan, Blaise L. Truesdell and Elizabeth J. Vrana. This work was supported by the Department of Energy’s Early Career Research Program.
Electrocatalytic grafting of polyvinyl chloride plastics
UTEP study: Zooplankton go “Eew!” to cleaning feces contaminated water
Sheds light on limitations of naturally occurring zooplankton for inactivating pathogen contaminated water
University of Texas at El Paso
image:
Scientists were recently surprised to find that the natural community of zooplankton — tiny, aquatic animals known to graze on bacteria — present in freshwater and saltwater do not clean water that is contaminated with fecal microorganisms. Pictured:One of the zooplankton found in the water samples is the adult copepod, a miniature crustacean that is about the size of the period at the end of this sentence.
EL PASO, Texas (Oct. 3, 2024) – Scientists at The University of Texas at El Paso and Stanford University were recently surprised to find that the natural community of zooplankton — tiny, aquatic animals known to graze on bacteria — present in freshwater and saltwater do not clean water that is contaminated with fecal microorganisms.
The research, published today in the biology journal mSphere, reveals important insights about the limitations of zooplankton in treating bodies of water that have been contaminated with fecal organisms, the team said. A 2017 U.S. water quality inventory revealed that over 50% of rivers, bays and estuaries were unsafe for at least one use, in many cases because of fecal contamination.
“When sewage is released into clean bodies of water and humans are exposed to it, it can lead to illness in humans,” said Lauren Kennedy, Ph.D., assistant professor of civil engineering at UTEP, who is the corresponding author on the study. “Our research seeks to understand what factors can render pathogens unable to infect people. In other words, how long does it take for the water to become safe for recreation again without any forms of outside intervention?”
Kennedy explained that water from sewage and septic tanks can accidentally enter bodies of freshwater as a result of accidents, inadequate water treatment or corroded infrastructure.
The authors hypothesized that zooplankton naturally present in water might graze on microorganisms from fecal contamination, inactivating the organisms and effectively “cleaning” the water.
To test this idea, the team added a virus called MS2 and the bacteria E.coli to samples of freshwater and saltwater taken from the San Francisco Bay area of California. MS2 and E.coli are considered useful proxies for scientific research, Kennedy said, because they are present at high concentrations in sewage and their presence often indicates fecal contamination in the environment. The water samples naturally contained both “large” particles like zooplankton, sand and dirt, and “small” or dissolved particles like salt.
They found that the large particles, including zooplankton, did not have a significant effect on the inactivation of the pathogen proxies. The small particles, however, seemed to have a greater impact. The pathogen proxies were inactivated at higher rates in high-salinity water, for example, ocean water taken from San Pedro Beach.
“I am proud that we were able to provide another perspective to consider for surface water remediation efforts,” Kennedy said.
The research, she added, is an important step forward in understanding the limits of zooplankton as natural “cleaners” of contaminated water. The next phases of the research will focus on the impact of salinity on pathogen survival in contaminated waters.
“I am proud to see this important work coming from our team,” said Carlos Ferregut, Ph.D., chair of the Department of Civil Engineering. “The research by Dr. Kennedy and her team provides valuable insights into the challenges of pathogen inactivation, especially in areas where wastewater can compromise human health.”
About The University of Texas at El Paso
The University of Texas at El Paso is America’s leading Hispanic-serving university. Located at the westernmost tip of Texas, where three states and two countries converge along the Rio Grande, 84% of our 24,000 students are Hispanic, and more than half are the first in their families to go to college. UTEP offers 170 bachelor’s, master’s and doctoral degree programs at the only open-access, top-tier research university in America.
You can bring plankton to fecal indicator organisms, but you cannot make the plankton graze: particle contribution to E. coli and MS2 inactivation in surface waters
