Earth

The scientific process is an iterative and collaborative journey. Research is published, others can weigh in on results, and hypotheses can be corroborated, refuted, or further refined and tested. Though it may seem like second guessing or perhaps become contentious in some cases, this often overlooked aspect of the scientific method makes science better by continuing to challenge scientific assertions, thereby expanding and deepening our understanding.

An example of this process has been published today in Proceedings of the National Academy of Sciences, in a collaboration between researchers from Louisiana State University, the University of Puerto Rico, and UConn. This new paper is a follow-up to an earlier response published in the same journal in 2018 that told of a collapsing food web and insect declines that were taking place in Puerto Rico, specifically as a result of global warming.

UConn Board of Trustees Distinguished Professor of Ecology and Evolutionary Biology and Executive Director of the Institute of the Environment, Mike Willig, and collaborators, have been working in Puerto Rico on long-term ecological research projects for decades, so when the paper came out, they took notice. The team includes lead author Timothy Schowalter and Manoj Pandey of LSU, Steven Presley also of UConn and Jess Zimmerman of the University of Puerto Rico.

"When we saw the initial paper and the claims of food web collapse we said, 'Well that is news to us!' but perhaps we weren't looking in the right places, or considering all of the possibilities. So we tried to, as science requires, see if the results were replicable or repeatable."

Willig explains that as insect populations appear to be on the decline in other areas of the world, the original paper on insect decline in Puerto Rico was among the first to claim declines due to global warming in a tropical setting. Willig and his collaborators decided to take a second look to see if they could corroborate the claims.

"We were not able to arrive at the same conclusions for a variety of reasons. The world is complex and there were a lot of problematic issues with the original research," Willig says the data that the authors of the initial paper selected and analytical approaches that they used were at the root of the problem. Critically, the original paper did not consider the complexities of the system, notably that Puerto Rico endures frequent hurricanes and tropical storms.

Nuances and long-term data changed the picture when looking at the original paper's hypothesis, says Willig,

"Many studies are like that first study in which part of the analyses involved two datasets, in this case taken 30 years apart. In contrast, our data looked at 29 years of annual research. Data can be consistent with one hypothesis but that doesn't make it right. Additionally, ecological research projects are often snapshots in time that correspond to the length of a grant, 3-5 years," says Willig. "That's why we're fortunate to have long-term data to disentangle the effects of warming from hurricane impacts and subsequent ecological succession."

Noting the flaws from the first study, the team used this long-term exploration as springboard to look deeper into their data to uncover trends of insect abundance.

"Puerto Rico is a disturbance-mediated environment where there are frequent hurricanes. Ecosystems in these disturbance-mediated environments are predisposed from an evolutionary perspective to be resistant to these storms," says Willig.

After a storm has blown through and brought down trees, the canopy is gone, temperatures on the ground increase, and leaves and other detritus becomes food for opportunists. Though a disaster for some species, these post-disturbance conditions lead to the perfect circumstances for a population boom in other species.

"The prediction is that due to global warming there will be an increase in the frequency of these high energy storms in the Caribbean. Storms will happen more often so that resident species will be evolving in a world dominated by more frequent hurricanes where habitats will represent early successional stages. The climatic environment and associated plant communities may move outside of tolerance limits of constituent animal species," says Willig.

"We see no species extinction on the site yet," but Willig notes that perhaps the original paper was right for the wrong reasons. Insect declines may not happen directly due to global warming but an increased hurricane frequency and intensity due to climate change could eventually push species beyond their limits.

"One of the cool things that came out of our study is that the hypothesis from the original food web collapse paper lead us to reanalyze our data in a way that we may not have done as quickly. It jarred us, it accelerated our desire to look at the data from multiple perspectives to try to disentangle the relative importance of warming, hurricanes and subsequent succession on the abundances of animal species, which is part of the self-correcting process of science. It also forces you to look outside the box and to examine your data to see how you can use it to distinguish between alternative hypotheses," says Willig.

The length of time over which data are collected adds value to those data. Long-term experiments are important for capturing the full story and nuances within a system. Willig likens the situation to regular medical checkups:

"The regular collection of data is important, like having annual checkups with your doctor. You may not be diabetic yet but your sugar levels may have been gradually increasing over the past 10 years, suggesting that there may be a problem. If you aren't doing regular checkups of the environment we will not have that early warning that environmental problems are on the horizon. It is the same with consistency, you can't fairly examine trends if you don't have comparable data at the same locations over a long term to assess ecosystem health."

Willig stresses that this new paper is not denying climate change is impacting insects around the world, but he emphasizes the need for more long-term monitoring of species abundances, and associated climatic and habitat data everywhere, to better understand what is going on in this time of rapid changes:

"What we are saying is that data are inadequate to show that global warming in Puerto Rico had an effect on the flora and fauna on the island, and in fact, we show that other climate change effects related to increasing hurricane frequency and intensity play a dominate role. Without long-term data from throughout the world, we don't know how general our result is compared to that other sites. It is necessary to have a network of sites collecting similar data in similar ways to see if a pattern is general regardless of geographic context."

All authors are part of the National Science Foundation's Long-term Ecological Research Program located at the Luquillo Experimental Forest (LUQ-LTER) in Puerto Rico.

Hydrogen is an important factor in a sustainable energy system. The gas stores energy in chemical form and can be used in many ways: as a fuel, a feedstock for other fuels and chemicals or even to generate electricity in fuel cells. One solution to produce hydrogen in a climate-neutral way is the electrochemical splitting of water with the help of sunlight. This requires photoelectrodes that provide a photovoltage and photocurrent when exposed to light and at the same time do not corrode in water. Metal oxide compounds have promising prerequisites for this. For example, solar water splitting devices using bismuth vanadate (BiVO4) photoelectrodes achieve already today ~8 % solar-to-hydrogen efficiency, which is close to the material's theoretical maximum of 9 %.

Theoretical limit is 20 % in α-SnWO4

To achieve efficiencies beyond 9 %, new materials with a smaller band gap are needed. The metal oxide α-SnWO4 has a band gap of 1.9 eV, which is perfectly suited for photoelectrochemical water splitting. Theoretically, a photoanode made of this material could convert ~20 % of the irradiated sunlight into chemical energy (stored in the form of hydrogen). Unfortunately, the compound degrades very quickly in an aqueous environment.

Protection against corrosion comes with a price

Thin layers of nickel oxide (NiOx) can protect the α-SnWO4 photoanode from corrosion, but were found to also significantly reduce the photovoltage. To understand why this is the case, a team led by Dr. Fatwa Abdi at the HZB Institute for Solar Fuels has analysed the α-SnWO4/NiOx interface in detail at BESSY II.

Interface explored at BESSY II

"We studied samples with different thicknesses of NiOx with hard X-ray photoelectron spectroscopy (HAXPES) at BESSY II and interpreted the measured data with results from calculations and simulations," says Patrick Schnell, the first author of the study and a PhD student in the HI-SCORE International Research School at HZB. "These results indicate that a thin oxide layer forms at the interface, which reduces the photovoltage," explains Abdi.

Outlook: better protection layers

Overall, the study provides new, fundamental insights into the complex nature of interfaces in metal oxide-based photoelectrodes. "These insights are very helpful for the development of low-cost, scalable metal oxide photoelectrodes," says Abdi. α-SnWO4 is particularly promising in this regard. "We are currently working on an alternative deposition process for NiOx on α-SnWO4 that does not lead to the formation of an interfacial oxide layer, which is likely to be SnO2. If this is successful, we expect that the photoelectrochemical performance of α -SnWO4 will increase significantly."

In a study of 500 sourdough starters spanning four continents, scientists have garnered new insights into the environmental factors that contribute to each sourdough starter's microbial ecosystem, and how different types of microbes influence both a sourdough's aroma and how quickly the sourdough rises. The results may surprise sourdough enthusiasts.

"We didn't just look at which microbes were growing in each starter," says Erin McKenney, co-author of the paper and an assistant professor of applied ecology at North Carolina State University. "We looked at what those microbes are doing, and how those microbes coexist with each other."

"There have been quite a few small studies on microbial ecosystems in sourdough," says Benjamin Wolfe, co-author of the study and an associate professor of biology at Tufts University. "We think this is the first large-scale study, building on all of that previous work."

For this study, the researchers collected 500 samples of sourdough starter, primarily from home bakers in the United States and Europe, though there were also samples from Australia, New Zealand and Thailand.

The researchers performed DNA sequencing on all 500 samples. Based on those findings, the researchers then selected 40 starters as being representative of the diversity they saw across the 500 submissions. Those 40 starters were then cultured and assessed in three ways.

First, the researchers worked with an expert panel of sensory professionals (think of them as super-sniffers) to assess each starter's aroma profile. Second, the researchers performed a chemical analysis of the volatile organic compounds being released by each starter. This analysis allowed the scientists to determine the structure of these aromatic compounds, as well as the relative amount of each of those compounds being released by each starter. Lastly, the researchers measured how quickly each of the forty starter doughs rose.

One of the findings that immediately struck the researchers was that geography didn't really matter (sorry, San Francisco).

"This is the first map of what the microbial diversity of sourdoughs looks like at this scale, spanning multiple continents," says Elizabeth Landis, co-lead author of the study and a Ph.D. student at Tufts. "And we found that where the baker lives was not an important factor in the microbiology of sourdough starters."

In fact, the findings challenge a lot of the conventional wisdom regarding sourdough.

"Lots of bakers felt sure that specific factors were responsible for variation between types of sourdough," McKenney says. "But what we found is that, while there could be tremendous variation between the microbial ecosystems of different sourdoughs, we could not find any single variable that was responsible for much of that variation."

"What we found instead was that lots of variables had small effects that, when added together, could make a big difference," says Angela Oliverio, co-lead author of the study and a former Ph.D. student at the University of Colorado, Boulder. "We're talking about things like how old the sourdough starter is, how often it's fed, where people store it in their homes, and so on."

The researchers were also surprised to see that 29.4% of the samples contained acetic acid bacteria (so named because they produce acetic acid).

"The sourdough research literature has focused almost exclusively on yeast and lactic acid bacteria," Wolfe says. "Even the most recent research in the field hadn't mentioned acetic acid bacteria at all. We thought they might be there to some extent, since bakers often talk about acetic acid, but we were not expecting anything like the numbers we found."

And, the researchers note, those acetic acid bacteria played a powerful role in shaping both the aroma of the sourdough and how quickly it grew. Specifically, the presence of acetic acid bacteria slowed the rise of sourdough, and gave it a vinegary smell.

Some of the findings were less surprising. For example, about 70% of the starters contained Saccharomyces cerevisiae, or baker's yeast. On the other hand, many people may be surprised that 30% of the sourdough starters didn't include the yeast most people associate with baking bread.

In fact, while the median starter contained only one type of yeast, the researchers found 70 different types of yeast across all 500 sourdough samples. So the potential variety is tremendous.

"I think it's also important to stress that this study is observational - so it can allow us to identify relationships, but doesn't necessarily prove that specific microbes are responsible for creating specific characteristics," Wolfe says. "A lot of follow-up work needs to be done to figure out, experimentally, the role that each of these microbial species and environmental variables plays in shaping sourdough characteristics."

"And while bakers will find this interesting, we think the work is also of interest to microbiologists," Landis says. "Sourdough is an excellent model system for studying the interactions between microbes that shape the overall structure of the microbiome. By studying interactions between microbes in the sourdough microbiome that lead to cooperation and competition, we can better understand the interactions that occur between microbes more generally - and in more complex ecosystems."

Manipulating individual electrons with the goal of employing quantum effects offers new possibilities and greater precision in electronics. However, these single-electron circuits are governed by the laws of quantum mechanics, meaning that deviations from error-free operation still occur - albeit (in the best possible scenario) only very rarely. Thus, insights into both the physical origin the and metrological aspects of this fundamental uncertainty are crucial for the further development of quantum circuitry. To this end, scientists from PTB and the University of Latvia have collaborated to develop a statistical testing methodology. Their results have been published in the journal Nature Communications.

Single-electron circuits are already used as electric-current quantum standards and in quantum-computer prototypes. In these miniaturized quantum circuits, interactions and noise impede the investigation of the fundamental uncertainties and measuring them is a challenge, even for the metrological precision of the measurement apparatus.

In the field of quantum computers, a testing procedure also referred to as a "benchmark" is frequently used in which the operating principle and fidelity of the entire circuit are evaluated via the accumulation of errors following a sequence of operations. Based on this principle, researchers from PTB and the University of Latvia have now developed a benchmark for single-electron circuits. Here, the circuit's fidelity is described by the random steps of an error signal recorded by an integrated sensor while the circuit repeatedly executes an operation. The statistical analysis of this "random walk" can be used to identify the rare but unavoidable errors when individual quantum particles are manipulated.

By means of this "random-walk benchmark", the transfer of individual electrons was investigated in a circuit consisting of single-electron pumps developed at PTB as primary standards for realizing the ampere, an SI base unit. In this experiment, sensitive detectors record the error signal with single-electron resolution. The statistical analysis made possible by counting individual particles not only shows fundamental limitations of the circuit's fidelity induced by external noise and temporal correlations but also provides a robust measure of assessing errors in applied quantum metrology.

The methodology developed within the scope of this work provides a rigorous mathematical foundation for validating quantum standards of electrical quantities and opens new paths for the development of integrated complex quantum systems.

Every year, more than 400,000 people die from malaria, the majority are children under the age of five years old, who die from a disease which affects more than 200 million people a year.

The most serious form of the disease is cerebral malaria which may cause severe neurological consequences and, in the worst-case scenario, result in death. The precise mechanism behind cerebral malaria has remained a mystery - until now, says a research group from the Department of Immunology and Microbiology at the University of Copenhagen.

'In our study, we show that a certain type of the malaria parasite can cross the blood-brain barrier by utilising a mechanism that is also used by immune cells in special cases. It is a major breakthrough in the understanding of cerebral malaria, and it partly explains the disease process seen in brain infections', says Professor Anja Ramstedt Jensen who, together with her colleague, Assistant Professor Yvonne Adams, has headed the study.

Malaria mimics immune cells

The blood-brain barrier is the guarding barrier between the brain´s blood vessels and the cells and other components that make up brain tissue. The barrier ensures that only certain molecules are allowed to pass through to the brain cells. It prevents harmful substances and microorganisms from crossing, but, in some cases, it allows the white blood cells which are an important part of our immune system to pass through.

'The malaria parasite takes up residence in red blood cells. However, since red blood cells cannot cross the blood-brain barrier, it has so far been our understanding that malaria parasites could not enter into brain tissue. Now we can show that the parasite is able to mimic the mechanism that the immune system's white blood cells use to cross the barrier, and we now know that this helps to explain the disease mechanism behind cerebral malaria', says Anja Ramstedt Jensen.

To investigate the mechanism behind cerebral malaria, the researchers have created a 3D model of the blood-brain barrier consisting of, among other things, brain cells which they have grown in cell culture. The method has so far been used in other contexts to study which drugs and peptides can cross the blood-brain barrier. But this is the first time the method has been used to study infections.

'This is completely new knowledge within malaria research. Previously, we have only been able to study how red blood cells with the malaria parasite bind to brain cells, but not whether they can penetrate brain cells', says Assistant Professor Yvonne Adams.

Based on this new method, the researchers are now in the process of further studying the molecular details that explain how malaria parasites penetrate the so-called endothelial cells, which are the cells in the blood-brain barrier that allow or reject access of molecules to our brain tissue.

'In addition, we are expanding our studies and the application of the method to other diseases such as Lyme disease, Borrelia, which is the most common cause of bacterial brain infection in Denmark and, among other things, causes meningitis and other forms of inflammation in the central nervous system', says Anja Ramstedt Jensen.

WASHINGTON -- A multi-institutional group of researchers has developed new metamaterial tiles that will help improve the sensitivity of telescopes being built at the preeminent Simons Observatory in Chile. The tiles have been incorporated into receivers that will be deployed at the observatory by 2022.

The Simons Observatory is the center of an ambitious effort to measure the cosmic microwave background -- electromagnetic radiation left over from an early stage of the universe -- using some of the world's largest and most sophisticated ground-based telescopes. These measurements will help improve our understanding of how the universe began, what it is made of and how it evolved into what it is today.

"The Simons Observatory telescopes will use a new ultra-sensitive millimeter-wave camera to measure the afterglow of the big bang with unprecedented sensitivity," said lead author Zhilei Xu from the University of Pennsylvania. "We developed a new low-cost absorbing tile that will be used in the camera to absorb environmental emissions that can obscure the signals we want to measure."

In the Optical Society (OSA) journal Applied Optics, the researchers show that the metamaterial microwave tiles they developed absorb more than 99 percent of millimeter wave radiation and retain their absorptive properties at the extremely low temperatures in which the millimeter-wave camera operates.

"Because the tiles can be made by injection molding commercially available materials, they are an economic, mass-producible and easy-to-install solution to what has been a long-standing problem," said Xu. "With this technology, the Simons Observatory will transform our understanding of the universe from many aspects, including the beginning of the universe, the formation and evolution of the galaxies and the ignition of the first stars."

Working at low temperatures

Ground-based millimeter-wave telescopes use receivers that are cooled to cryogenic temperatures to reduce noise and thus boost sensitivity. Receiver technology has advanced to the point where any amount of stray light can degrade the image while also decreasing the sensitivity of the detector. A better way to suppress stray light within the receivers would further increase their sensitivity to the very faint signals coming from deep within space.

However, developing a material that can suppress stray light while operating at such extremely low temperatures is quite challenging. Previous attempts resulted in materials that either couldn't be cooled effectively to cryogenic temperatures or didn't achieve the necessary combination of low reflectance and high absorption. Other solutions have also tended to be difficult to install or challenging to mass produce.

To overcome these challenges, the researchers turned to metamaterials because they can be engineered to achieve specific properties that don't occur in nature. After complex electromagnetic simulation studies, the researchers designed metamaterials based on a material that combined carbon particles and plastic.

Reducing reflection

Although the plastic composite exhibited high absorption in the desired microwave region of the electromagnetic spectrum, the surface reflected a significant amount of radiation before it could get inside the material to be absorbed. To reduce the reflection, the researchers added an anti-reflective coating that was tailored using injection molding.

"The low-reflectance surface combined with high-absorption bulk material allowed the metamaterial absorber tiles to deliver excellent suppression of unwanted signals at cryogenic temperatures close to absolute zero," said Xu.

After ensuring that tiles made of the new metamaterial could mechanically survive thermal cycles from room temperatures to cryogenic temperatures, the researchers verified that they could be effectively cooled to -272° C (-458° F) and then measured their optical performance. "We developed a custom test facility to measure the performance of the tiles with high fidelity," said Grace Chesmore, a graduate student at the University of Chicago who led the optical measurements of this research. The testing showed that the metamaterial exhibited excellent reflectance properties with low scattering and that it absorbed almost all of the incoming photons.

"As detector sensitivity continues to improve for millimeter-wave telescopes, it becomes crucial to control scattered photons," said Xu. "The successful combination of a metamaterial and injection molding manufacturing opens up many possibilities for millimeter-wave instrument scientific instrument design."

UNIVERSITY PARK, Pa. -- The actions that older adults take on Facebook may be more important to their user experience and well-being than their overall use of the site, according to researchers.

In a study conducted by a team that included researchers from Penn State, older adults experienced different levels of competence, relatedness and autonomy on Facebook based on the types of their activities on the site.

Specifically, older adults who posted more pictures to Facebook felt more competent, which led to significantly higher levels of well-being in general, according to the researchers, who report their findings in the journal Health Communication. Commenting more frequently and receiving more responses to posts -- also called message contingency -- tended to improve feelings of relatedness and connection with others on Facebook, they added. Further, older adults who customized their profiles gave them more of a sense of autonomy while on the site.

However, the researchers also found that overall Facebook use was linked to lower well-being among older adults. Although this may seem to contradict the previous results, it may actually tell a more nuanced story about the relationship between social media and well-being, said S. Shyam Sundar, James P. Jimirro Professor of Media Effects in the Donald P. Bellisario College of Communications and co-director of the Media Effects Research Laboratory.

"What it may boil down to is that older adults might want to reduce their overall use of the platform, but still engage more in those specific Facebook activities that can enhance their sense of competence, like posting photos," said Sundar, who is also an affiliate of Penn State's Institute for Computational and Data Sciences (ICDS). "The recommendation is, then, rather than just browsing through feed after feed after feed on Facebook, actually do something on Facebook that can promote these positive outcomes."

According to Eun Hwa Jung, assistant professor of communication, Kookmin University, South Korea, and lead author of the study, the study addresses the large gap in understanding about how older people engage on social media.

"Much of the social media research out there focuses on younger people because they tend to be the main users of the technology, but older adults are also becoming more used to technology and are using social media more," said Jung. "So, this study hopefully offers older adults ways to use social media to enhance their positive mental health."

Designing social media features to help older adults feel less isolated and more connected is especially important because this group is vulnerable to social isolation, according to the researchers.

"In general, older adults have a higher risk of being socially isolated because of mobility restrictions," said Sundar. "Back in 2009, what really prompted this research was our curiosity about whether social networking sites could help them bridge that gap with their contacts and help them overcome that social isolation. With the COVID-19 restrictions, there's even greater social isolation for older adults, which means there's even greater need for social connection."

The researchers said that developers may want to find ways to ease the complexity of tasks on social media sites that help older users build confidence and promote their well-being.

"Designers could ease the friction that older adults may feel when they post photos, for example," said Sundar. "If they post a photo on Facebook, they might feel like it's gone into a vacuum -- the site doesn't give them immediate feedback on how to post that photo, or whether the photo is on the site yet. Interfaces could be better designed to be friendly to older adults, so that they can more easily post multimedia elements."

To gather data for the study, the researchers conducted both a content analysis and an online survey of about 202 Facebook users who were more than 60 years old. A content analysis is a rigorous study of pieces of media, such as text or videos. To do that, Jung, formerly a doctoral student at Penn State, assembled data about content posted by study participants, who all agreed to allow her to carefully record their activity on the social media site during the one-year study period.

The participants also filled out an online survey that measured psychological feelings, such as subjective well-being, enjoyment and autonomy.

According to the researchers, future research could look at features and tasks associated with other social media sites, such as Twitter and Pinterest, as well as investigate other technological features on social media sites.

Heart disease is a killer threat for southern sea otters feasting on domoic acid in their food web, according to a study led by the University of California, Davis.

The study, published in the journal Harmful Algae, examined the relationship between long-term exposure to domoic acid and fatal heart disease in southern sea otters, a threatened marine mammal.

"Sea otters are an amazing indicator of what's happening in the coastal environment, not just to other marine animals, but to us, too, especially on the issue of domoic acid," said Christine K. Johnson, director of the EpiCenter for Disease Dynamics in the One Health Institute at the UC Davis School of Veterinary Medicine and senior author of the study.

IN HOT WATER

Domoic acid is a neurotoxin that accumulates in the food web, contaminating crabs and clams -- common prey for sea otters. It is produced by harmful algal blooms, which typically occur when water is unusually warm. For example, a massive warm water "blob" in 2015 created a widespread toxic bloom along the West Coast, causing domoic acid levels to spike and forcing the closure of that season's Dungeness crab fishery.

Climate change projections indicate that toxic blooms and domoic acid exposure will continue to rise. The world's ocean temperatures in 2020 were the third highest on record, and all five of the oceans' hottest years on record occurred in the past five years.

OVER-EXPOSED OTTERS

To identify the ecological drivers of heart disease, the scientists combined several domoic acid datasets with detailed life history data from 186 free-ranging southern sea otters in California from 2001 to 2017. Of those animals, necropsy reports show that heart disease was a cause of death for 34 of the 48 otters that died during that time.

The scientists found that domoic acid exposure increased a sea otter's risk of dying with heart disease 1.7-fold. The risk is up to 2.5 times greater for otters consuming a high proportion of crab and clam, which accumulate domoic acid in their tissues, helping it persist in the food web.

The study was also the first to demonstrate a disturbing and unexpected trend: Domoic acid exposure is especially detrimental for prime-age adult sea otters, whose survival is vital for population growth.

"That's worrisome for the long-term population recovery of southern sea otters, which are a threatened species," said lead author Megan Moriarty, a wildlife veterinarian who conducted this research for her Ph.D. in epidemiology at UC Davis. "This study emphasizes that domoic acid is a threat that isn't going away. It's a food web toxin and is pretty pervasive."

Infection with Toxoplasma gondii, a parasite associated with wild and feral cat feces on land that makes its way to the ocean, also increased the risk of fatal heart disease 2.4-fold.

Co-author Melissa Miller, a veterinarian and pathologist with the California Department of Fish and Wildlife and a UC Davis One Health Institute affiliate, recently led a separate study analyzing the causes of death of sea otters.

"Improving our understanding of the effects of domoic acid on the health and population recovery of southern sea otters is extremely important" said Miller of the domoic acid study. "Given their unique biology and specialized diet, sea otters are extremely vulnerable to toxic algal blooms, which are likely to worsen with climate change. So the results of this work have far-reaching implications."

Philadelphia, January 26, 2021 - Researchers at Children's Hospital of Philadelphia (CHOP) and the University of Pennsylvania found female and male collegiate athletes take approximately the same amount of time to recover from a concussion, with subtle differences in recovery time depending on the type of sports being played and the division level of the sport. The findings suggest that equity in access to sports medical care among college athletes may be contributing to these similar outcomes.

The findings, derived as part of the CARE (Concussion Assessment, Research and Education) Consortium, were recently published online by the British Journal of Sports Medicine.

Some previous studies have indicated that female athletes may experience longer times to recovery and more lost time from sports due to sport-related concussions. However, other studies have found no differences, but many of these studies were conducted with smaller cohorts and may not have comprehensively accounted for a variety of additional extrinsic factors, including injury setting (practice vs. competition), mechanism of injury (person vs. equipment), and timing of reporting and seeking medical care.

In order to provide a more definitive picture of potential differences between the sexes in concussion injury and recovery, this study examined data collected by the CARE Consortium, funded jointly by the NCAA and the Department of Defense, representing the largest multi-center prospective study of concussion in collegiate athletes to date. In this study, colleges collected extensive pre- and post-injury data in a large, prospective cohort of thousands of collegiate athletes.

"I think many people are concerned that, based on intrinsic biological differences, female athletes may have longer paths to recovery from concussions than their male counterparts," said Christina L. Master, MD, a sports medicine pediatrician and Co-Director of the Minds Matter Concussion Program at CHOP and first author of the study. "However, to better understand any potential biologically-based sex differences in concussion injury and recovery, we needed a large study like this that could better account for extrinsic factors that are not biological."

The study collected data on 1,071 concussions that occurred between 2014 and 2017 across more than 30 colleges, universities and service academies participating in the CARE Consortium. Among those concussions, there was no statistically significant difference in recovery between males and females. Female athletes had a median of 13.5 days before returning to play compared with 11.8 days for males (p=0.96).

Subtle differences were seen between certain subgroups in the study. Females took slightly longer to recover than males from concussions sustained in contact sports (12.7 days for females vs 11 days for males, p=0.00201), while male athletes took longer to recover than females from concussions they experienced in limited contact sports (16.85 days for males vs 13.8 days for females, p

Master said these subtle differences could be attributed to a variety of factors, including differential access to athletic training and sports medical resources. For instance, Division I sports may have greater levels of athletic training and sports medicine support compared with Division II and III sports. In the case of male athletes experiencing longer recovery time for limited contact sports, this may be related to fewer resources allocated to limited contact men's sports than contact men's sports where concussions are assumed to be more likely to occur. Another potential explanation may be that rules and regulations limiting exposure to impacts in men's contact sports may have had a mitigating effect on concussions in men's contact sports. This, coupled with the fact that women took longer than men to recover in contact sports, but not in limited contact sports, suggests that these differences between men and women cannot be entirely accounted for simply on the basis of biological sex.

"This study makes a strong case for equity in access to specialized athletic training and sports medical care," Master said. "Title IX, which mandates equal access for both women and men to resources, such as sports, including athletic training and sports medical care, may have potentially helped to close any gap that exists in outcomes between the sexes. In the instances where recovery times did differ between the sexes, a re-examination of resource allocation might achieve a more equitable distribution to maximize outcomes for all athletes."

The rate at which ice is disappearing across the planet is speeding up, according to new research.

And the findings also reveal that the Earth lost 28 trillion tonnes of ice between 1994 and 2017 - equivalent to a sheet of ice 100 metres thick covering the whole of the UK.

The figures have been published today (Monday, 25 January) by a research team which is the first to carry out a survey of global ice loss using satellite data.

The team, led by the University of Leeds, found that the rate of ice loss from the Earth has increased markedly within the past three decades, from 0.8 trillion tons per year in the 1990s to 1.3 trillion tons per year by 2017.

Ice melt across the globe raises sea levels, increases the risk of flooding to coastal communities, and threatens to wipe out natural habitats which wildlife depend on.

The findings of the research team, which includes the University of Edinburgh, University College London and data science specialists Earthwave, are published in European Geosciences Union's journal The Cryosphere.

The research, funded by UK Natural Environment Research Council, shows that overall, there has been a 65 % increase in the rate of ice loss over the 23-year survey. This has been mainly driven by steep rises in losses from the polar ice sheets in Antarctica and Greenland.

Lead author Dr Thomas Slater, a Research Fellow at Leeds' Centre for Polar Observation and Modelling , said: "Although every region we studied lost ice, losses from the Antarctic and Greenland ice sheets have accelerated the most.

"The ice sheets are now following the worst-case climate warming scenarios set out by the Intergovernmental Panel on Climate Change. Sea-level rise on this scale will have very serious impacts on coastal communities this century."

Dr Slater said the study was the first of its kind to examine all the ice that is disappearing on Earth, using satellite observations .

He added: "Over the past three decades there's been a huge international effort to understand what's happening to individual components in Earth's ice system, revolutionised by satellites which allow us to routinely monitor the vast and inhospitable regions where ice can be found.

"Our study is the first to combine these efforts and look at all the ice that is being lost from the entire planet."

The increase in ice loss has been triggered by warming of the atmosphere and oceans, which have warmed by 0.26°C and 0.12°C per decade since the 1980, respectively. The majority of all ice loss was driven by atmospheric melting (68 %), with the remaining losses (32%) being driven by oceanic melting.

The survey covers 215,000 mountain glaciers spread around the planet, the polar ice sheets in Greenland and Antarctica, the ice shelves floating around Antarctica, and sea ice drifting in the Arctic and Southern Oceans.

Rising atmospheric temperatures have been the main driver of the decline in Arctic sea ice and mountain glaciers across the globe, while rising ocean temperatures have increased the melting of the Antarctic ice sheet. For the Greenland ice sheet and Antarctic ice shelves, ice losses have been triggered by a combination of rising ocean and atmospheric temperatures.

During the survey period, every category lost ice, but the biggest losses were from Arctic Sea ice (7.6 trillion tons) and Antarctic ice shelves (6.5 trillion tons), both of which float on the polar oceans.

Dr Isobel Lawrence, a Research Fellow at Leeds' Centre for Polar Observation and Modelling, said: "Sea ice loss doesn't contribute directly to sea level rise but it does have an indirect influence. One of the key roles of Arctic sea ice is to reflect solar radiation back into space which helps keep the Arctic cool.

"As the sea ice shrinks, more solar energy is being absorbed by the oceans and atmosphere, causing the Arctic to warm faster than anywhere else on the planet.

"Not only is this speeding up sea ice melt, it's also exacerbating the melting of glaciers and ice sheets which causes sea levels to rise."

Half of all losses were from ice on land - including 6.1 trillion tons from mountain glaciers, 3.8 trillion tons from the Greenland ice sheet, and 2.5 trillion tons from the Antarctic ice sheet. These losses have raised global sea levels by 35 millimetres.

It is estimated that for every centimetre of sea level rise, approximately a million people are in danger of being displaced from low-lying homelands.

Despite storing only 1 % of the Earth's total ice volume, glaciers have contributed to almost a quarter of the global ice losses over the study period, with all glacier regions around the world losing ice.

Report co-author and PhD researcher Inès Otosaka, also from Leeds' Centre for Polar Observation and Modelling, said: "As well as contributing to global mean sea level rise, mountain glaciers are also critical as a freshwater resource for local communities.

"The retreat of glaciers around the world is therefore of crucial importance at both local and global scales."

Just over half (58 %) of the ice loss was from the northern hemisphere, and the remainder (42 %) was from the southern hemisphere.

AUGUSTA, Ga. (January 25, 2021) - Immediately after a traumatic brain injury and as long as one year later, there are increased levels of immune cells called ILCs in the brain promoting inflammation, which can worsen brain damage, scientists report.

They also report for the first time that the cell energy sensor AMPK is a brake that can stop what becomes a chronic state of destructive inflammation driven by these ILCs, or innate lymphoid cells.

"We think ILCs are kind of a master regulator of all that inflammation happening within the brain," says Dr. Krishnan Dhandapani, neuroscientist in the Department of Neurosurgery at the Medical College of Georgia at Augusta University. "It's like the thermostat in the room."

They report in the journal JCI Insight that using the common diabetes drug metformin to turn up AMPK, an enzyme essential to maintaining sufficient energy inside cells, restores a healthier balance between the three known subtypes of ILCs, says Dr. Babak Baban, immunologist and associate dean for research in the Dental College of Georgia at AU.

"It's not just in TBI, it's in arthritis, Alzheimer's, you get this positive feedback loop of tissue damage which leads to inflammation which leads to more tissue damage and more inflammation," says corresponding author Dhandapani. "That is what we are trying to break."

The scientists from MCG and DCG call TBI a worldwide public health issue, which kills or debilitates three million people each year. About one-third of patients hospitalized with a TBI die from brain damage that occurs weeks or months after the initial injury. Those who survive have an increased risk of dementia and cognitive decline. Ongoing inflammation in the brain parallels the ongoing damage and loss of function, but standard anti-inflammatory therapies have not really improved outcomes, they write.

Therapies that target and decrease sources of increased inflammation, like the ILC subtypes ILC1 and ILC3, following a TBI, and increase expression of the anti-inflammatory subtype ILC2, are needed, they write.

In their TBI model, for example, within a day of injury, they found increases in all three ILC subtypes in the meninges, the membranous covering of the brain and spinal cord. Also, levels of ILC2 and ILC3 remained higher a year out, along with chronic inflammation as well as about a 50% reduction in activation of AMPK and ongoing problems with energy use.

They found similar patterns of increased proinflammatory ILCs within the dura, the tougher, outmost layer of the meninges that is just under the skull, as well as the cerebral spinal fluid of patients who had experienced a moderate to severe TBI and needed a procedure called a decompressive craniectomy to relieve pressure on their brain. By comparison, ILC levels were low in the cerebrospinal fluid of patients with an excess of fluid in the brain called hydrocephalus.

In their model, when they completely removed the "brake" AMPK, problems worsened, with the biggest increases in the proinflammatory subtypes resulting in relentless inflammation and death.

When they delivered metformin directly into the cerebrospinal fluid to better target ILCs and instead activate AMPK, it expanded the overall pool of ILC subtypes, inhibited the two inflammation-producing subtypes and mice exhibited improved movement and behavior. The commonly used diabetes drug also prompted a similar shift away from proinflammatory T-cells, drivers of the immune response, and toward regulatory T cells, which also dampen inflammation.

AMPK is essentially a switch that metformin is known to flip, says first author Baban. "It drives everything back toward these counter-inflammatory ILC2s," Dhandapani adds. "It brought the seesaw back under control."

Baban notes that after a severe attack like a TBI, it can take the body years to bring the resulting inflammation under control and restore homeostasis. The severity of the injury is an important factor in how long it takes to restore balance, Baban says. "We want to bring it out of the chronic mode," he adds.

They think it's the ILCs in the protective, three-layer meninges that respond to the 911 call a TBI triggers that can do that. Their findings also likely apply to other acute brain injuries like strokes.

The coordinated development of immune responses profoundly influences brain injury outcomes, they write, and ILCs function like "cerebral immune gatekeepers" relaying information from the brain to the immune system, then deciding which immune cells make it to the brain, where they can start, stop and generally adjust inflammation.

ILCs like to function within cell tissue and they are already present, albeit in small, fairly inactive numbers, in the brain and all body tissue, Baban says. They typically sit on the mucosal border of tissues, like the membranous meninges. When a TBI happens, for example, the ILCs respond to things like tissue fragments and cell contents that get spilled, and that they should not be seeing.

"How does a TBI induce a regulated immune response within the brain is the first question," Dhandapani says, and they have previously published findings of inflammation-promoting T cells moving in a predictable pattern while inflammation-suppressing regulatory T cells were suppressed. They suspected and now have shown that ILCs are critical to regulation of the immune response to a TBI. The next logical question was can they do something to reduce the proinflammatory environment that lingered.

They also found, as expected, after a TBI, expression of AMPK, a master energy sensor and regulator in the body that makes adjustments like activating glucose, when cell energy gets low, and increasing generation of the cell fuel ATP, was inhibited which increased ILC expansion.

Baban notes that ILCs are very reactive to their immediate surroundings so anything that could manipulate that microenvironment, even diet, might help enable the shift they prompted with the drug metformin.

One of their next steps include exploring the use of cell therapy to directly deliver more ILC2s rather than using metformin to prompt their increase. They also want to know what switches the switch and better understand how the environment inside the brain changes after a traumatic event. That includes better understanding the relationship of the inflammation that lingers but dwindles over time and the ongoing injury that appears to linger with it.

They both note that inflammation is invaluable to the initial response to and recovery from a TBI, that it's the chronic inflammation that can result that is problematic. Their ultimate goals include fine tuning inflammation in the aftermath of injury to ensure it does not ultimately cause more harm than good.

While more work is still needed, the level and complement of ILCs in the cerebrospinal fluid also may prove a sound biomarker of which patients are at risk for this increasing neurological damage in the weeks and months after their initial injury, they say, and be a way to monitor the effectiveness of treatment as well that activates AMPK.

Immediately following a TBI, there actually is a brief period of hyperactivity, rapidly followed by a prolonged period of decreased glucose consumption by brain cells, which reduces energy, which is associated with a host of problems from seizures to impaired cognition. Reduced AMPK following a brain injury also contributes to brain function problems like impaired cognition and seizures.

ILCs can be found in tissue throughout a developing baby as well as an adult. ILCs also are known to direct macrophages, which can literally scarf up damaged tissue. The dysregulation of ILCs can also lead to autoimmune disease and allergies. Metformin is effective in diabetes by improving the way the body handles insulin and reducing the amount of sugar released by the liver. It's known effect on AMPK likely also means it lowers inflammation, which is rampant in diabetes.

ILCs have been characterized by MCG and DCG scientists as a SWAT team of immune cells, which they have previously found in breast milk -- likely one way mothers afford immune protection to their babies -- and in the lip tissue removed from babies who have cleft lip and palate surgery, which likely helps explain typically low infection rates following surgery in a body area typically considered one of the dirtiest. They've also found them in the periodontium, the tissue that surrounds and supports the teeth.

Despite significant methodological and technological advancements in chemical recycling of synthetic polymers, an effective mechanochemical PET degradation has not yet been described in the scientific literature, until now! Vjekoslav Štrukil from the Ruđer Bošković Institute (RBI), Zagreb, Croatia, found that the challenging breakdown of waste PET under ambient conditions of temperature and pressure can be achieved by mechanochemical ball milling or vapor-assisted aging.

These results were published in the prestigious journal ChemSusChem and thanks to the remarkable reviews, the paper was ranked among the top five percent publications in the field, thus earning a Very Important Paper (VIP) status. Furthermore, the editorial board featured this study on its cover.

Plastic pollution has become one of the most complex environmental issues, especially in the context of increasing production and demand for plastic materials. While innovations in polymer chemistry have radically changed our lives in the mid-20th century, the outstanding properties of plastics such as durability, chemical stability, strength and many other pose a serious problem when such materials are to be recycled.

According to some estimates, by the year 2050 there will be more plastic waste than fish in oceans by total weight, with the annual production of plastic materials reaching more than 1.1 billion tonnes.

Global production of plastics in 2015 was estimated to approximately 380 million tonnes, and the cumulative amount of waste generated from 1950s until 2015 was around 6.3 billion tonnes.

Only 9% of the waste was recycled and a staggering 60% of all plastics ever made ended up in the environment.

Rationalizing the use of plastic products and increasing the consumer awareness to sort and recycle waste is important in terms of pollution reduction.

However, finding technical solutions and methodologies to more efficiently process plastic waste and transform it into valuable chemicals still poses a great challenge to researchers around the world.

Polyethylene terephthalate (PET) is a synthetic polyester widely used in the production of soft-drink bottles and textile fibres. PET is a thermoplastic made of repeating units of terephthalic acid and ethylene glycol, linked together via an ester bond. Hence the popular name polyester, which is mostly used in the textile industry.

The ester linkage can be cleaved by hydrolysis to transform PET waste back into its monomer constituents.
Current chemical methods of PET recycling require the use of organic solvents at high temperatures and pressures to achieve depolymerization into monomer derivatives in practical yields.

Exploring the possibilities of using ball milling in the process of PET depolymerization, Dr. Vjekoslav Štrukil from the RBI Laboratory for Physical-Organic Chemistry successfully decomposed PET into monomer terephthalic acid at ambient temperature and pressure, with terephthalic acid being also the starting material for the production of this plastic.

Mechanochemistry has recently become one of the most promising fields of chemical science due to its extremely high efficiency, simplicity, speed, and the ability to significantly reduce the use of toxic organic solvents or completely avoid their use in chemical reactions.

''Although the International Union of Pure and Applied Chemistry (IUPAC) ranked mechanochemistry, as well as the degradation of polymers into monomers, among the top ten innovations in chemistry that will change the world, an effective mechanochemical PET degradation has not yet been described in the scientific literature'', says Dr Štrukil.

In the latest study Dr Štrukil describes a highly efficient alkaline hydrolysis of waste PET in the solid state at ambient temperature and pressure, achieved by mechanochemical ball milling with PET conversion and monomer isolated yields up to 99%.

Excellent yields were also achieved by the so-called vapor-assisted aging of manually mixed or pre-milled solid mixtures of PET and sodium hydroxide in a humid environment or in the presence of alcohol vapors. Aging in alcohol vapors represents an even milder route to PET depolymerization with 99% conversion at room temperature.

"Some of the experiments started just before the lockdown in March, followed by an earthquake. Of course, all this has slowed down and almost completely shut down the research. This meant those results were completely lost and we had to start our research all over again after the lockdown. However, that surreal situation has brought some new ideas, so when I returned to work in May, I focused my research on the aging of PET plastics at ambient temperature and pressure in vapors of different liquid phases such as acetonitrile, methanol or ethanol ", explains Dr Štrukil.

Published results show that mechanochemical milling and vapor-assisted aging, as two complementary solid-state techniques, have the potential for alkaline degradation of waste PET plastics and PET textile on larger scales as well. The described methodology could serve as a platform for the development of new and efficient environmentally-friendly processes for production of terephthalic acid from waste PET abundant in the environment, instead of non-renewable sources such as fossil fuels.

Arctic sea ice is rapidly diminishing due to global warming, and scientists have found that sea ice dynamics have a big impact on circulation and precipitation patterns in Arctic Alaska, which lies at a climatological crossroads between the Arctic and North Pacific Oceans. Recent studies--most of which focus on current trends in the region and on what will happen in the future--have shown that circulation patterns in the Arctic and North Pacific Oceans influence one another.

Doctoral candidate Ellie Broadman of Northern Arizona University's School of Earth and Sustainability wanted to learn about this relationship on a longer timescale, so she developed and led a study in Arctic Alaska to investigate it. She is the lead author on a paper detailing her team's findings, "Coupled impacts of sea ice variability and North Pacific atmospheric circulation on Holocene hydroclimate in Arctic Alaska," which was recently published in the prestigious journal Proceedings of the National Academy of Sciences.

The team, which included NAU Regents' Professor and prominent paleoclimatologist Darrell Kaufman and four noted British scientists as collaborators, compiled a new record of hydroclimatic change over the past 10,000 years in Arctic Alaska, revealing that periods of reduced sea ice result in isotopically heavier precipitation derived from proximal Arctic moisture sources. The researchers supported their findings about this systematic relationship through isotope-enabled model simulations and a compilation of regional paleoclimate records.

"We developed a new paleoclimate dataset from a lake sediment core that was collected in Arctic Alaska," Broadman said. "That record extends back nearly 10,000 years, and we used it to understand precipitation patterns in the past. We combined that dataset with some model simulations and a bunch of previously published paleoclimate records and interpreted all those different puzzle pieces to try to get a sense of what was happening at a large scale."

"Using all these datasets, we showed that there's evidence for a relationship between sea ice in the Arctic and atmospheric circulation in the North Pacific in the past, and that those dynamics can make it wetter or drier in Arctic Alaska. Understanding these long-term dynamics are important for understanding what will happen in the future, because they give us an idea of how different parts of the climate system have responded to one another previously. They reveal some natural processes that are important to understand as we look at the impact of global warming."

Broadman was drawn to paleoclimate research while pursuing her undergraduate degree in geography, which she enjoyed because of its interdisciplinary nature.

"I loved thinking about the connections between natural and human systems. I started working in the paleoecology lab to get some research experience and got hooked. You can do so many things with mud! You can study the influence of humans on the environment, or how fire and vegetation changed over time, or look at really large-scale climate processes, like I did in this paper. And just like geography, paleoclimatology is so interdisciplinary: it draws people from all kinds of academic backgrounds, from anthropology, to ecology, to math and physics and beyond. I love working with people who have all these different backgrounds and interests. I also love learning about the Earth's climate system, and I wanted to become an expert in climate science. So, when I decided to go to graduate school, it was an easy decision to work in this interdisciplinary, climate-focused field."

Broadman chose NAU's PhD program in Earth Sciences and Environmental Sustainability for her graduate career. "The main reason I came to NAU was to work with Darrell Kaufman, my advisor. He has an incredible reputation; he does super-interesting and important research and it was a major selling point that his research program is focused on Alaska. As someone interested in climate change, I was drawn to the Arctic. It feels exciting and extremely relevant to study a region where climate is changing faster than anywhere else on the planet. Getting to do field work in Alaska, and specifically in the Arctic National Wildlife Refuge, was a bonus!"

"As I set out to earn my PhD, my goal was to contribute about the North Pacific, the Arctic, sea ice and how those processes work together to influence climate in Arctic Alaska. It's very satisfying to feel like I accomplished that goal, and I think it feeds the part of my brain that loves to think in terms of big, interconnected systems."

Broadman, who plans to graduate in April, is currently applying for a variety of positions. Her interests include policy, land management and science communications as well as teaching and research.

A nuclear war could trigger an unprecedented El Niño-like warming episode in the equatorial Pacific Ocean, slashing algal populations by 40 percent and likely lowering the fish catch, according to a Rutgers-led study.

The research, published in the journal Communications Earth & Environment, shows that turning to the oceans for food if land-based farming fails after a nuclear war is unlikely to be a successful strategy - at least in the equatorial Pacific.

"In our computer simulations, we see a 40 percent reduction in phytoplankton (algae) biomass in the equatorial Pacific, which would likely have downstream effects on larger marine organisms that people eat," said lead author Joshua Coupe, a post-doctoral research associate in the Department of Environmental Sciences in the School of Environmental and Biological Sciences at Rutgers University-New Brunswick. "Previous research has shown that global cooling following a nuclear war could lead to crop failure on land, and our study shows we probably can't rely on seafood to help feed people, at least in that area of the world."

Scientists studied climate change in six nuclear war scenarios, focusing on the equatorial Pacific Ocean. The scenarios include a major conflict between the United States and Russia and five smaller wars between India and Pakistan. Such wars could ignite enormous fires that inject millions of tons of soot (black carbon) into the upper atmosphere, blocking sunlight and disrupting Earth's climate.

With an Earth system model to simulate the six scenarios, the scientists showed that a large-scale nuclear war could trigger an unprecedented El Niño-like event lasting up to seven years. The El Niño-Southern Oscillation is the largest naturally occurring phenomenon that affects Pacific Ocean circulation, alternating between warm El Niño and cold La Niña events and profoundly influencing marine productivity and fisheries.

During a "nuclear Niño," scientists found that precipitation over the Maritime Continent (the area between the Indian and Pacific oceans and surrounding seas) and equatorial Africa would be shut down, largely because of a cooler climate.

More importantly, a nuclear Niño would shut down upwelling of deeper, colder waters along the equator in the Pacific Ocean, reducing the upward movement of nutrients that phytoplankton - the base of the marine food web - need to survive. Moreover, the diminished sunlight after a nuclear war would drastically reduce photosynthesis, stressing and potentially killing many phytoplankton.

"Turning to the sea for food after a nuclear war that dramatically reduces crop production on land seems like it would be a good idea," said co-author Alan Robock, a Distinguished Professor in the Department of Environmental Sciences at Rutgers-New Brunswick. "But that would not be a reliable source of the protein we need, and we must prevent nuclear conflict if we want to safeguard our food and Earth's environment."

In a study of local rivers, experts at the University of Nottingham in the UK have discovered more invertebrates - animals without a backbone, such as insects and snails - living on litter than on rocks.

In urban rivers where there are no better alternatives, litter provided the largest, most stable and complex habitat available for invertebrates to live on.

The findings could have important implications for the management of urban rivers, including how river clean-up events are conducted.

The research team, in the School of Geography, studied three local rivers; the River Leen, Black Brook, and Saffron Brook, in Leicestershire and Nottinghamshire by collecting samples of rocks and litter from the riverbeds to compare in their laboratory.

The scientists found that the surfaces of the litter were inhabited by different and more diverse communities of invertebrates than those on rocks. Plastic, metal, fabric, and masonry samples consistently had the highest diversity, meanwhile, glass and rock samples were considerably less diverse than other material samples.

They observed that flexible pieces of plastic, like plastic bags, were inhabited by the most diverse communities and speculated that the types of invertebrates they found on flexible plastic suggests it might mimic the structure of water plants.

The study is the first of its kind to evaluate the role of litter as a riverine habitat and has been published in the journal Freshwater Biology.

Hazel Wilson, project lead in the School of Geography at the University of Nottingham, said: "Our research suggests that in terms of habitat, litter can actually benefit rivers which are otherwise lacking in habitat diversity. A diverse community of invertebrates is important because they underpin river ecosystems by providing food for fish and birds, and by contributing to carbon/nutrient cycling."

"However, this does not justify people littering. We absolutely should be working towards removing and reducing the amount of litter in freshwaters - for many reasons, including the release of toxic chemicals and microplastics, and the danger of animals ingesting or becoming entangled with litter. Our results suggest that litter clearance should be combined with the introduction of complex habitat, such as tree branches or plants to replace that removed during litter picks."

The authors say that their findings highlight the poor environmental quality in many urban rivers, given that the most complex habitat left for invertebrates is litter. They hope to build on this research by investigating which characteristics of litter enable it to support greater biodiversity, and how it compares to complex natural habitats, like water plants or pieces of wood.

Hazel Wilson added: "This could help us discover methods and materials to replace the litter habitat with alternative and less damaging materials when we conduct river clean-ups".