Author: getwetprojectblog

Today, NOAA-supported scientists announced that this year’s Gulf of Mexico “dead zone”— an area of low to no oxygen that can kill fish and marine life—is approximately 3,275 square miles. That’s more than 2 million acres of habitat potentially unavailable to fish and bottom species—larger than the land area of Rhode Island and Delaware combined.

The five-year average dead zone size (also known as the hypoxic zone) is now 4,280 square miles, which is over two times larger than management targets. Since records began in 1985, the largest hypoxic zone measured was 8,776 square miles in 2017.

The measurement was made during an annual survey cruise, led by a team of scientists from Louisiana State University and the Louisiana Universities Marine Consortium (LUMCON) aboard the R/V Pelican during the last week of July. The information gathered is a key metric used by the Mississippi River/Gulf of Mexico Watershed Hypoxia Task Force to measure progress toward achieving their five-year average target of 1,900 square miles or smaller by 2035. The cruise provides a one-time snapshot of the dead zone; the five-year average captures the dynamic and changing nature of the zone over time.

“Yearly measurements enable us to help decision-makers fine tune strategies to reduce the size of the hypoxic zone in these waters and mitigate harmful impacts to our coastal resources and economy,” said Nicole LeBoeuf, director of NOAA’s National Ocean Service. “While some hypoxia is natural, the size and scale of what we’ve seen here in the last several decades is unusually large and detrimental. Our measurements and analyses can empower communities to take action to protect their coasts and contribute to the region’s economic sustainability.”

In June, NOAA forecasted an average-sized hypoxic zone of 5,364 square miles, based primarily on Mississippi River discharge and nutrient runoff data from the U.S. Geological Survey. The measured size fell within the uncertainty range for the models which factors in some of the inherent environmental variability of the system such as the below average river discharge over the summer. This demonstrates the overall accuracy of the models and their ability to be applied as tools for nutrient reduction strategies. 

“This summer was an unusual year for Gulf hypoxia,” said Nancy Rabalais, Ph.D. professor at Louisiana State University and LUMCON, who is the principal investigator. “The Mississippi River discharge was below the summer average. The lower flow is unable to support the normal layering of the water column, allowing dissolved oxygen from the surface waters to diffuse more easily to the seabed. The ecosystem subject to hypoxia was characterized by lower turbidity, lower algal biomass, lower nutrients and higher salinity in the surface waters.”

Each year, excess nutrients from cities, farms and other sources in upland watersheds drain into the Gulf and stimulate algal growth during the spring and summer. The algae eventually die, sink and decompose. Throughout this process, oxygen-consuming bacteria decay the algae and consume the oxygen. The resulting low oxygen levels near the bottom are insufficient to support most marine life, rendering the habitat unusable and forcing species to move to other areas to survive. 

Exposure to hypoxic waters has been found to alter fish diets, growth rates, reproduction, habitat use and availability of commercially harvested species like shrimp. This year, for the first time, scientists from NOAA Fisheries and North Carolina State University began using an experimental model to better understand where shrimp could be found relative to the hypoxic zone. 

Investments in understanding and addressing hypoxia

The Hypoxia Task Force is accelerating progress in reducing excess nutrients in the Mississippi/Atchafalaya River Basin by promoting collaboration among federal partners, states, farmers and other stakeholders. 

“The dead zone in the Gulf of Mexico is a stark reminder that water quality and land stewardship go hand in hand,” said Environmental Protection Agency (EPA) Assistant Administrator for Water Radhika Fox. “At EPA, we recognize this and are investing $60 million through President Biden’s Bipartisan Infrastructure Law in work that states are doing to reduce excess nutrients that feed the dead zone.”

In June, the EPA announced $60 million over the next five years to fund nutrient reduction efforts through the Gulf Hypoxia Program. The funding will significantly expand and enhance the capacity of the states to improve water quality in the Gulf and throughout the Mississippi/Atchafalaya River Basin. To support the work of the Hypoxia Task Force, EPA will also deepen its existing collaborations with the agricultural community, seek new partnerships and identify and elevate examples of producer innovation.

“Hypoxia Task Force states are focused on implementing our state-based and science-driven nutrient reduction strategies and scaling up and accelerating the adoption of proven water quality and conservation practices. The addition of new partnerships with both public and private partners in both urban and rural settings will pay big water-quality dividends in the future,” said Mike Naig, Iowa Secretary of Agriculture and co-chair of the Hypoxia Task Force. “We know that innovative changes on the land lead to positive changes in the water, and these investments benefit communities across our states and our neighbors downstream. As we take on this challenge and carry out our work in priority watersheds across the Mississippi River Basin in the years ahead, we are grateful to EPA and our other partners who provide needed support for these important efforts.”

FOR MORE INFORMATION: https://phys.org/news/2022-08-below-average-gulf-mexico-dead-zone.html

Researchers at CU Boulder have developed and validated a new sensor for E. coli risk detection that features an impressive 83% accuracy rate when detecting contamination in surface waters.

The findings were recently published in Water Research and could improve detection of a variety of contaminants quickly and effectively in water systemsaround the globe and in America.

Emily Bedell (Ph.D.EnvEngr’22) is the lead author on the paper from the Mortenson Center in Global Engineering. She said about two billion people worldwide use a drinking water source that has some level of fecal matter in it and can cause health issues ranging from diarrhea to stunted growth—especially in young children. 

“About 60% of all diarrheal deaths are related to water quality, globally,” she said. “This is a real problem, but current methods for finding poop in drinking water are expensive, have high barriers to entry like extensive training requirements or can take about 24 hours to provide results. We have invented a sensor combined with a machine learning model that uses fluorescence to show fecal contamination spikes in real-time.” 

Both the sensor and machine learning model combination have been approved for a patent by the U.S. Patent Office.

Bedell said fluorescence works by shining a UV LED light source on a water sample and measuring the amount of light that is absorbed and re-emitted at a higher wavelength. That information can quickly show potential contamination, but it is sensitive to many environmental and physical factors such as sample temperature, which cause noise in the data and make it difficult to interpret.

“We use machine learning techniques to cut through that noise to better detect anomalies,” Bedell said.

Fast and accurate assessment of water quality is a growing need—not only in low-income countries, but in situations like the Flint, Michigan water crisis where citizens were exposed to dangerous levels of lead from poor government policies. 

Professor Evan Thomas, director of the Mortenson Center, is a co-author on the paper. He said climate change is also a factor in this discussion as more frequent power outages may impact treatment facility operations and severe weather could contaminate critical water sources.

“We are going to need more data on water quality, and we need it to be widely available,” he said. “Taking measurements once a day will not be enough to ensure we are receiving water that doesn’t have either biological or chemical contaminants that can harm us in both the short and long term.” 

Bedell is now employed as an engineer for Virridy in Boulder and is working on advancing the technology further. Ideally it will function in partnership with a larger home treatment system for those utilizing a private well—where water quality is not regulated by the EPA—for their drinking water. 

“That sensor will be a miniaturized version of the design built in this paper and will be installed on a house’s main water line coming from the well,” she said. “The sensor’s data will be sent through the user’s WiFi to an online database where the machine learning model will be applied to predict risk level and send the information to a mobile app that will alert the user if contamination is detected.” 

Bedell said she has always been interested in the intersections of engineering, the environment and social equity and this research project really brought those aspects together during her time with the Mortenson Center.

“Water quality research hits on all those points in so many ways. With more data we can explicitly point out how and when communities are being harmed through environmental injustices so that the policies and practices put in place that caused the harm can be addressed,” she said.

FOR MORE INFORMATION: https://phys.org/news/2022-08-highly-accurate-sensor-coli.html

Once, a river ran through it. Now, white dust and thousands of dead fish cover the wide trench that winds amid rows of trees in France’s Burgundy region in what was the Tille River in the village of Lux.

From dry and cracked reservoirs in Spain to falling water levels on major arteries like the Danube, the Rhine and the Po, an unprecedented drought is afflicting nearly half of Europe. It is damaging farm economies, forcing water restrictions, causing wildfires and threatening aquatic species.

There has been no significant rainfall for almost two months in the continent’s western, central and southern regions. In typically rainy Britain, the government officially declared a drought across southern and central England on Friday amid one of the hottest and driest summers on record.

And Europe’s dry period is expected to continue in what experts say could be the worst drought in 500 years.

Climate change is exacerbating conditions as hotter temperatures speed up evaporation, thirsty plants take in more moisture and reduced snowfall in the winter limits supplies of fresh water available for irrigation in the summer. Europe isn’t alone in the crisis, with drought conditions also reported in East Africa, the western United States and northern Mexico.

As he walked in the 15-meter (50-foot) wide riverbed in Lux, Jean-Philippe Couasné, chief technician at the local Federation for Fishing and Protection of the Aquatic Environment, listed the species of fish that had died in the Tille.

“It’s heartbreaking,” he said. “On average, about 8,000 liters (2,100 gallons) per second are flowing. … And now, zero liters.”

In areas upstream, some trout and other freshwater species can take shelter in pools via fish ladders. But such systems aren’t available everywhere.

Without rain, the river “will continue to empty. And yes, all fish will die. … They are trapped upstream and downstream, there’s no water coming in, so the oxygen level will keep decreasing as the (water) volume goes down,” Couasné said. “These are species that will gradually disappear.”

Jean-Pierre Sonvico, the regional head of the federation, said diverting the fish to other rivers won’t help because those waterways also are affected.

“Yes, it’s dramatic because what can we do? Nothing,” he said. “We’re waiting, hoping for storms with rain, but storms are very local so we can’t count on it.”

The European Commission’s Joint Research Center warned this week that drought conditions will get worse and potentially affect 47% of the continent.

Andrea Toreti, a senior researcher at the European Drought Observatory, said a drought in 2018 was so extreme that there were no similar events for the last 500 years, “but this year, I think, it is really worse.”

For the next three months, “we see still a very high risk of dry conditions over Western and Central Europe, as well as the U.K.,” Toreti said.

Current conditions result from long periods of dry weather caused by changes in world weather systems, said meteorologist Peter Hoffmann of the Potsdam Institute for Climate Impact Research near Berlin.

“It’s just that in summer we feel it the most,” he said. “But actually the drought builds up across the year.”

Climate change has lessened temperature differences between regions, sapping the forces that drive the jet stream, which normally brings wet Atlantic weather to Europe, he said.

A weaker or unstable jet stream can bring unusually hot air to Europe from North Africa, leading to prolonged periods of heat. The reverse is also true, when a polar vortex of cold air from the Arctic can cause freezing conditions far south of where it would normally reach.

Hoffmann said observations in recent years have all been at the upper end of what existing climate models predicted.

FOR MORE INFORMATION: https://phys.org/news/2022-08-european-drought-dries-rivers-fish.html

Laws intended to protect the environment in European cities must be more flexible in order to protect residents from the climate emergency, experts have warned.

More “adaptive” legislation and governance is needed if urban areas are to cope with changing temperatures and ecosystems, the study says.

Researchers say current environment law plays a part in protecting cities, but also stops them building resilience.

The study, by Tony Arnold from the University of Louisville and Tiago de Melo Cartaxo from the University of Exeter—and both from the Exeter Center for Environmental Law—is published in the book “Urban Climate Resilience.”

Dr. de Melo Cartaxo said, “European cities could arguably be world leaders in bringing together climate adaptation, given the multiple layers of laws and institutional frameworks involving urban environments and environmental rights. As promising as urban and environmental laws in Europe may be, they do not yet fully have the adaptive institutional characteristics nor the justice- and capacity-building characteristics that are needed to merge climate adaptation with justice for and among marginalized and oppressed communities.”

The study says it is key for cities to be governed in a resilient way, which reflects the fact that the environment, politics, the economy and social conditions are connected.

Instead many laws prioritize the protection of natural resources and the environment and focus on a single goal such as protecting water quality, rather than the functions and viabilities of broader systems, such as ecosystem-society dynamics or the composition of neighborhoods, will be affected by disturbances such as climate change or gentrification.

Professor Arnold said, “While European cities will benefit in their climate adaptation strategies from EU-level directives, top-down regulations, and coordination among networks of cities, they will also need legal and governance structures that create or maintain authority to act at local, sub-local, private, public-private, and community-commons levels. This will allow innovation and adaption to local contexts and lessens the risk of policy failures. They have high tolerance for uncertainty, whereas many legal systems demand certainty, which is incompatible with environmental or climate realities.”

The study also warns too much flexibility and discretion by decision-makers and policy implementers can lead to abuses of power and violations of rights. An adaptive legal framework must live together with conventional legal frameworks, as part of a whole system.

Dr. de Melo Cartaxo said, “Adaptive law is not the solution; it is one additional and important solution improving how institutions function with complexity, uncertainty, instability, and inequalities.

“The adaptive multi-tool characteristics of climate-adaptationgovernance in European cities should be harnessed to address the many vulnerabilities that marginalized communities face and that affect their capacities to adapt to climate change. These include: housing supply, affordability, and quality; food insecurity; energy insecurity and environmental injustices.

“Climate-adaptation laws, plans, and policies should include specific resilience-justice goals and targets, as well as mandatory mechanisms for reporting and monitoring of the many variables and conditions that affect the adaptive capacities of marginalized communities.”

FOR MORE INFORMATION: https://phys.org/news/2022-08-european-cities-legal-flexibility-residents.html

The entire ecosystem of the planet, including humans, depends on clean water. When carbonate rock weathers, karst areas are formed, from which around a quarter of the world’s population obtains its drinking water. Scientists have been studying how quickly pollutants can reach groundwater supplies in karst areas and how this could affect the quality of drinking water. An international team led by Junior Professor Dr. Andreas Hartmann of the Chair of Hydrological Modeling and Water Resources at the University of Freiburg compared the time it takes water to seep down from the surface to the subsurface with the time it takes for pollutants to decompose in carbonate rock regions in Europe, North Africa and the Middle East. The researchers published their results in the scientific journal Proceedings of the National Academy of Sciences (PNAS).

Previous continental or global hydrologic model applications have focused mainly on the occurrence of floods or droughts and the general availability of drinking water. However, scientists have predominantly neglected water quality as an important factor for the potability of water on these large scales, in particular how quickly pollutants can seep from the earth’s surface into the groundwater through cracks or fissures.

The current research results of Hartmann and his team show that in karst regions, which are characterized by an increased occurrence of cracks or fissures, the risk of pollution by degradable pollutants such as pesticides, pharmaceuticals or pathogens is significantly higher than previously expected. Although pollutants are considered short-lived, up to 50 percent of them can still reach groundwater, depending on the period of their decomposition. The main reason for this, the researchers show, is rapid seepage pathways that allow large amounts of infiltrating water to reach groundwater in a short time. Particularly in regions with thin soils, such as the Mediterranean region, pollutants on the surface can thus seep quickly and in high concentrations into the subsurface during large rain events. Hartmann’s researchers demonstrated the consequences using the example of the degradable pesticide Glyphosate. According to their calculations, the rapid transport of Glyphosate into the groundwater can cause it to exceed its permissive values by a factor of up to 19. The increased risk of pollution for drinking water or ecosystems that depend on groundwater is particularly relevant for regions where agriculture depends on degradable fertilizers and pesticides.

FOR MORE INFORMATION: https://www.sciencedaily.com/releases/2021/05/210517124940.htm

An invisible flow of groundwater seeps into the ocean along coastlines all over the world. Scientists have tended to disregard its contributions to ocean chemistry, focusing on the far greater volumes of water and dissolved material entering the sea from rivers and streams, but a new study finds groundwater discharge plays a more significant role than had been thought.

The new findings, published January 8 in Nature Communications, have implications for global models of biogeochemical cycles and for the interpretation of isotope records of Earth’s climate history.

“It’s really hard to characterize groundwater discharge, so it has been a source of uncertainty in the modeling of global cycles,” said first author Kimberley Mayfield, who led the study as a graduate student at UC Santa Cruz. “It took a large effort by researchers around the world who came together to make this happen.”

The researchers focused on five key elements — lithium, magnesium, calcium, strontium, and barium — measuring concentrations and isotope ratios in coastal groundwater at 20 sites around the world, and using previously published data from additional sites.

“Those elements are important because they come from the weathering of rocks, and weathering of silicate rocks accounts for a huge uptake of carbon dioxide from the atmosphere over long time scales,” Mayfield explained.

Coauthor Adina Paytan, a research professor in UCSC’s Institute of Marine Sciences, said groundwater is an important source of inputs to the oceans, but has been easy to ignore because it is unseen and hard to measure.

“This is the first global assessment of groundwater discharge for most of these elements,” Paytan said. “This information is useful for our understanding of how weathering of rock is related to climate, not only in the present but also in the past.”

The study estimated that the amount of these elements entering the sea from groundwater is at least 5%, and up to 16%, of the contributions from rivers based on the latest global groundwater flux estimates. The results also showed that the isotopic composition of groundwater discharge can be different from that of rivers.

“The composition of groundwater discharge is very dependent on coastal geology, whereas river water is more influenced by the interiors of continents,” Mayfield said. “It’s important to recognize that groundwater makes a difference globally, and now that we have this large data set, people can keep improving it with more sampling and develop better models of global groundwater discharge.”

FOR MORE INFORMATION: https://www.sciencedaily.com/releases/2021/01/210108084110.htm

The study, published in Nature Geoscience, produced a global model mapping pollution risk caused by 92 chemicals commonly used in agricultural pesticides in 168 countries.

The study examined risk to soil, the atmosphere, and surface and ground water.

The map also revealed Asia houses the largest land areas at high risk of pollution, with China, Japan, Malaysia, and the Philippines at highest risk. Some of these areas are considered “food bowl” nations, feeding a large portion of the world’s population.

University of Sydney Research Associate and the study’s lead author, Dr Fiona Tang, said the widespread use of pesticides in agriculture — while boosting productivity — could have potential implications for the environment, human and animal health.

“Our study has revealed 64 percent of the world’s arable land is at risk of pesticide pollution. This is important because the wider scientific literature has found that pesticide pollution can have adverse impacts on human health and the environment,” said Dr Tang.

Pesticides can be transported to surface waters and groundwater through runoff and infiltration, polluting water bodies, thereby reducing the usability of water resources.

“Although the agricultural land in Oceania shows the lowest pesticide pollution risk, Australia’s Murray-Darling basin is considered a high-concern region both due to its water scarcity issues, and its high biodiversity,” said co-author Associate Professor Federico Maggi from the School of Civil Engineering and the Sydney Institute of Agriculture.

“Globally, our work shows that 34 percent of the high-risk areas are in high-biodiversity regions, 19 percent in low-and lower-middle-income nations and five percent in water-scarce areas,” said Dr Tang.

There is concern that overuse of pesticides will tip the balance, destabilise ecosystems and degrade the quality of water sources that humans and animals rely on to survive.

The future outlook

Global pesticide use is expected to increase as the global population heads towards an expected 8.5 billion by 2030.

“In a warmer climate, as the global population grows, the use of pesticides is expected to increase to combat the possible rise in pest invasions and to feed more people,” said Associate Professor Maggi.

Dr Tang said: “Although protecting food production is essential for human development, reducing pesticide pollution is equivalently crucial to protect the biodiversity that maintains soil health and functions, contributing towards food security.”

Co-author Professor Alex McBratney, Director of the Sydney Institute of Agriculture at the University of Sydney, said: “This study shows it will be important to carefully monitor residues on an annual basis to detect trends in order to manage and mitigate risks from pesticide use.”

“We recommend a global strategy to transition towards a sustainable, global agricultural model that reduces food wastage while reducing the use of pesticides,” said the authors of the paper.

FOR MORE INFORMATION: https://www.sciencedaily.com/releases/2021/03/210330092530.htm

A new method could help to track groundwater changes better than before. To this end, researchers from Potsdam and Oberlin, Ohio (USA), have compared gravity field data from the GRACE and GRACE-Follow On satellite missions with other measuring methods. They investigated the seasonal water storage in almost 250 river basins in Asia, whose water regime is dominated by monsoon. The results allow the large-scale GRACE data to be scaled down to smaller regions. The researchers report on this in the journal Earth and Planetary Science Letters.

Knowledge of underground water storage is of existential importance for agriculture as well as for the drinking water supply in many regions. These reservoirs are replenished by precipitation and seeping water, which in turn feeds rivers and lakes and allows rivers to flow in dry seasons. Measurements, however, are difficult because it is difficult to look into the earth, so one has to rely on either point values only — via boreholes and wells — or on calculations from precipitation and runoff data.

Since 2002 there has been another method of measuring groundwater changes: Via the GRACE satellite missions (from 2002 to 2017) and GRACE-Follow On (since 2018), the change in the amount of water in and on the earth can be determined on the basis of its gravity field signal. But this method also has its pitfalls. First, the mass changes measured by the GRACE-FO satellites say nothing about the depth in which the mass is located: Do lakes empty at the surface? Is the level of rivers falling? Or does water drain from deeper layers? Secondly, the GRACE-FO satellites provide data for comparatively large areas of several tens of thousands of square kilometres. It is currently not possible to resolve the gravity field data more precisely.

In a new study, Amanda H. Schmidt from Oberlin College, Ohio, together with researchers from the German Research Centre for Geosciences, is showing how different methods can be cleverly combined to obtain reliable groundwater data even for small river basins. They have examined monsoon rainfall data and seasonal water storage in almost 250 river basins in Asia. The size of the individual areas varies from one thousand to one million square kilometres. The study covers almost all of Asia.

The water balance on our planet is characterized by three main variables: precipitation, surface runoff and evaporation. The difference of these goes into or flows out of various reservoirs, e.g. the groundwater. Time series of measuring stations on rivers (hydrographs) after persistent precipitation show typical falling curves (so-called recession curves), which reflect the emptying of water reservoirs. Groundwater fluctuations can be estimated from these curves. Another method is the comparison of precipitation and runoff values by the time delay of the runoff; the temporary intermediate storage results in a so-called P-Q hysteresis. P stands for precipitation and Q for runoff. The area or size of the hysteresis loop can be used as a measure for the intermediate storage.

The study in Earth and Planetary Science Letters now shows that the P-Q hysteresis and the gravity field data of GRACE missions are strongly correlated. According to the study, both reflect seasonal groundwater changes very well. As a consequence, this means that a combination of precipitation and runoff data and GRACE gravity field data can also be used to record groundwater in catchment areas that are only about 1000 square kilometres in size.

FOR MORE INFORMATION: https://www.sciencedaily.com/releases/2020/07/200715111431.htm

A study of 29 European lakes has found that some naturally-occurring lake bacteria grow faster and more efficiently on the remains of plastic bags than on natural matter like leaves and twigs.

The bacteria break down the carbon compounds in plastic to use as food for their growth.

The scientists say that enriching waters with particular species of bacteria could be a natural way to remove plastic pollution from the environment.

The effect is pronounced: the rate of bacterial growth more than doubled when plastic pollution raised the overall carbon level in lake water by just 4%.

The results suggest that the plastic pollution in lakes is ‘priming’ the bacteria for rapid growth — the bacteria are not only breaking down the plastic but are then more able to break down other natural carbon compounds in the lake.

Lake bacteria were found to favour plastic-derived carbon compounds over natural ones. The researchers think this is because the carbon compounds from plastics are easier for the bacteria to break down and use as food.

The scientists caution that this does not condone ongoing plastic pollution. Some of the compounds within plastics can have toxic effects on the environment, particularly at high concentrations.

The findings are published today in the journal Nature Communications.

“It’s almost like the plastic pollution is getting the bacteria’s appetite going. The bacteria use the plastic as food first, because it’s easy to break down, and then they’re more able to break down some of the more difficult food — the natural organic matter in the lake,” said Dr Andrew Tanentzap in the University of Cambridge’s Department of Plant Sciences, senior author of the paper.

He added: “This suggests that plastic pollution is stimulating the whole food web in lakes, because more bacteria means more food for the bigger organisms like ducks and fish.”

The effect varied depending on the diversity of bacterial species present in the lake water — lakes with more different species were better at breaking down plastic pollution.

A study published by the authors last year found that European lakes are potential hotspots of microplastic pollution.

When plastics break down they release simple carbon compounds. The researchers found that these are chemically distinct to the carbon compounds released as organic matter like leaves and twigs break down.

The carbon compounds from plastics were shown to be derived from additives unique to plastic products, including adhesives and softeners.

The new study also found that bacteria removed more plastic pollution in lakes that had fewer unique natural carbon compounds. This is because the bacteria in the lake water had fewer other food sources.

The results will help to prioritise lakes where pollution control is most urgent. If a lake has a lot of plastic pollution, but low bacterial diversity and a lot of different natural organic compounds, then its ecosystem will be more vulnerable to damage.

“Unfortunately, plastics will pollute our environment for decades. On the positive side, our study helps to identify microbes that could be harnessed to help break down plastic waste and better manage environmental pollution,” said Professor David Aldridge in the University of Cambridge’s Department of Zoology, who was involved in the study.

The study involved sampling 29 lakes across Scandinavia between August and September 2019. To assess a range of conditions, these lakes differed in latitude, depth, area, average surface temperature and diversity of dissolved carbon-based molecules.

The scientists cut up plastic bags from four major UK shopping chains, and shook these in water until their carbon compounds were released.

At each lake, glass bottles were filled with lake water. A small amount of the ‘plastic water’ was added to half of these, to represent the amount of carbon leached from plastics into the environment, and the same amount of distilled water was added to the others. After 72 hours in the dark, bacterial activity was measured in each of the bottles.

The study measured bacterial growth — by increase in mass, and the efficiency of bacterial growth — by the amount of carbon-dioxide released in the process of growing.

In the water with plastic-derived carbon compounds, the bacteria had doubled in mass very efficiently. Around 50% of this carbon was incorporated into the bacteria in 72 hours.

“Our study shows that when carrier bags enter lakes and rivers they can have dramatic and unexpected impacts on the entire ecosystem. Hopefully our results will encourage people to be even more careful about how they dispose of plastic waste,” said Eleanor Sheridan in the University of Cambridge’s Department of Plant Sciences, first author of the study who undertook the work as part of a final-year undergraduate project.

FOR MORE INFORMATION: https://www.sciencedaily.com/releases/2022/07/220726132524.htm

Throughout the middle of the 20th century, phosphorus inputs from detergents and fertilizers degraded the water quality of Switzerland’s Lake Geneva, spurring officials to take action to remediate pollution in the 1970s.

“The obvious remedy was to reverse the phosphorus loading, and this simple idea helped enormously, but it didn’t return the lake to its former state, and that’s the problem,” said George Sugihara, a biological oceanographer at UC San Diego’s Scripps Institution of Oceanography.

Sugihara, Boston University’s Ethan Deyle, and three international colleagues spent five years searching for a better way to forecast and manage Lake Geneva’s ecological response to the threat of phosphorus pollution, to which the effects of climate change must now be added. The team, including Damien Bouffard of the Swiss Federal Institute of Aquatic Sciences and Technology, published its new hybrid empirical dynamic modeling (EDM) approach on June 20 in the journal Proceedings of the National Academy of Sciences.

“Nature is much more interconnected and interdependent than scientists would often like to think,” said Sugihara, the McQuown Chair Professor of Natural Science at Scripps. EDM can help in this context as a form of supervised machine learning, a way for computers to learn patterns and teach researchers about the mechanisms behind the data.

“You pull one lever and everything else changes, whack-a-mole style. Single-factor experiments, the hallmark of 20th-century science where everything is held constant, can teach you a lot in principle, but it is not how the world works,” he said.

“If this were not the case, if nature behaved more like the single-factor experiments and was less connected and interdependent, we’d be able to predict outcomes with simple models where relationships don’t change.”

Interdependence and changing relationships are the reality of ecosystems and they are also the reality of financial markets where prediction is so challenging, Sugihara noted. EDM was honed in the crucible of financial forecasting in the mid 1990s through the early 2000s when Sugihara was a managing director at Deutsche Bank.

Sugihara has drawn upon his financial background to design market tools for supporting sustainable marine fisheries for the last 20 years at Scripps. He calls EDM “math without equations.”

But EDM is not a black box method, said Deyle, referring to quantitative methods based on mysterious mathematical or computational formulas. It is a criticism he says is often raised about machine learning.

“Rather, it uses the data to tell you in the most direct way, with minimal assumptions, what is going on. What are the important variables? How do the relationships change through time? It has a mechanism and transparency that comes directly from the data.”

What Sugihara’s team has attempted departs from traditional modeling methods used in recent decades. As Deyle notes, parts of the well-established models are represented by constants.

“The fixed and constant force of gravity, or the shape and depth of a lake, for example. Consequently, physical processes in the lake can be very well modeled with simple equations,” he said.

Not so for the changing ecology and biochemistry.

“The organisms driving change in an ecosystem like Lake Geneva’s have changed over the last two decades. The food web has changed, and is constantly changing, along with the lake biochemistry,” Bouffard said.

“The standard tools are ill-suited for such problems,” said Deyle, who received his Ph.D. in biological oceanography from Scripps Oceanography with adviser Sugihara in 2015.

“Lake Geneva is one of the most well-studied systems in the world. It’s not a coincidence that it was an opportunity to push the envelope with a machine-learning approach to ecological forecasting,” Deyle said.

The authors demonstrate that their hybrid approach not only leads to substantially better prediction, but also to a more actionable description of the processes (such as biogeochemical and ecological) that drive water quality.

Notably, the hybrid model suggests that the impact on water quality of raising air temperature by 3 degrees Celsius (5.4 degrees Fahrenheit) would be on the same order as the phosphorus pollution of the previous century, and that best management practices may no longer involve a single control lever such as reducing phosphorus inputs alone.

“One of the intellectual cornerstones of all this is minimalism,” Sugihara said. “Extracting information out of data with the fewest assumptions.”

A simple model that predicts target data yet to be collected is more convincing than a complex model that may agree with current thinking and can be made to “fit” history remarkably well, but does not actually “predict” events yet to be seen. This was the major issue in financial applications, where it is easy to find things that “fit,” but nearly impossible to find anything that actually “predicts.”

“The more complicated something is, the easier it is to fool yourself,” he said. “Our hybrid approach seems to have a balance that works.”

Study co-authors include Victor Frossard, Université Savoie Mont Blanc; Robert Schwefel and John Melack, University of California Santa Barbara.

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FOR MORE INFORMATION: https://phys.org/news/2022-06-hybrid-machine-lake-ecosystem-responses.html