Study shows how climate impacts food webs, poses socioeconomic threat in Eastern Africa

Climate impacts on Lake Tanganyika are a bellwether for global change worldwide, team says

UNIVERSITY OF KENTUCKY

Research News

 

IMAGE: THE RESEARCH TEAM SPENT 12 DAYS ON LAKE TANGANYIKA COLLECTING CORE SAMPLES FROM THE LAKE'S FLOOR. THEY CHARTERED A CONGOLESE MERCHANT VESSEL, SEEN HERE, AND ADAPTED IT FOR THEIR RESEARCH... view more 

CREDIT: MICHAEL MCGLUE, UNIVERSITY OF KENTUCKY

LEXINGTON, Ky. (Oct. 9, 2020) -- A new study is sounding the alarm on the impact climate change could have on one of the world's most vulnerable regions.

Michael McGlue, Pioneer Natural Resources Professor of Stratigraphy in the University of Kentucky Department of Earth and Environmental Sciences, and his team conducted the study at Lake Tanganyika -- a major African fishery. The results, which published today in Science Advances, show how certain changes in climate may place the fishery at risk, potentially diminishing food resources for millions of people in this area of eastern Africa.

"Lake Tanganyika's fish are a critically important resource for impoverished people from four nations (Tanzania, Democratic Republic of the Congo, Burundi and Zambia) and resilience to environmental change in that region is quite low," McGlue said. "Our study revealed that high frequency variability in climate can lead to major disruptions in how the lake's food web functions."

Small pelagic fish, known locally as dagaa, are abundant in Lake Tanganyika, and their conservation is pivotal to the food security and economy of rapidly growing and largely impoverished segments of these four nations.

Dagaa feed on algae and plankton, which means greater algae production in the lake results in more fish. How this aquatic food web responds to external forces, like climate, is critical for identifying vulnerabilities and maintaining healthy fish stocks. But until now, very limited information existed on how Lake Tanganyika may respond to such forces.

To understand how the lake reacts to climate changes, the team would need detailed information on the lake's upwelling -- the process by which deep waters rise and fertilize surface waters, thereby increasing algae and photosynthesis. In order to observe this, the team would have to obtain data from well-preserved sediment cores within the lake.

McGlue and his team traveled to one of the most remote regions of Lake Tanganyika, the southern basin, on a 12-day trip to collect these cores from the lake floor.

Lead author and University of Kentucky Professor Michael McGlue (right) and chief engineer M. Mupape celebrate the successful recovery of core LT17-2A, the first of its kind from southern Lake Tanganyika. Until now, sedimentary records from the lake lacked the resolution needed to accurately measure the influence of frequent climatic events, such as the El Nino Southern Oscillation.

"The winds were especially violent that season, so most of our cruise was spent taking refuge from the waves in bays near the shoreline," McGlue said. "But in the narrow window when the winds dropped, we raced out to our stations and collected the cores."

McGlue and his team would later "read" the layers of sediment.

"The chemistry and fossil content of each layer tells us a specific story about how the lake functions," McGlue said. "Limnologists (scientists who study the lake today, like our co-author Dr. Ismael Kimirei) help us to translate the information in the sedimentary record and learn how climate change affects the lake's food web."

Until now, sedimentary records from Lake Tanganyika lacked the resolution needed to accurately measure the influence of frequent climatic events, such as the El Nino Southern Oscillation (ENSO). Most sedimentary datasets are low resolution, meaning that changes can only be detected over wide intervals of time, such as thousands of years. Conditions within certain areas of Lake Tanganyika converged to provide high temporal resolution of its sediment, which McGlue and his team were the first to sample.

"We were able to detect changes that were happening in Lake Tanganyika over very short intervals of time (e.g., months or years) using these sediments," McGlue said. "This is quite rare -- and crucial -- for using the data to guide fisheries management and conservation practices. Designing effective strategies for fisheries management using low resolution data is a challenge, because environmental changes that affect the food web can occur rapidly."

The team observed increases in algae production due to high solar irradiance -- the amount of energy from the sun that reaches Earth's atmosphere. According to the study, the convergence of high solar irradiance and La Nina results in a strong monsoon and upwelling, which increases algae in southern Lake Tanganyika. In contrast, a monsoon weakened by low solar irradiance and El Nino, as well as warmer surface waters, results in weak or absent upwelling and low algae production.

"(These samples provide) the detail that is necessary to capture abrupt change associated with teleconnective (climate) processes," said Jeffery Stone, co-author from Indiana State University.

The team says the socioeconomic threat these conditions create for sub-Saharan Africa is the most severe of any region on Earth, but they believe their findings can help guide long-term management practices.

"Armed with this knowledge, fisheries management strategies can be designed to help cope with these challenges," McGlue said.

Kimirei, who is also director-general of the Tanzania Fisheries Research Institute (TAFIRI), says the findings of this study are a critical building block toward research-informed policymaking in the Lake Tanganyika region.

"The importance of fisheries to the food security of the east and central African nations cannot be overemphasized," he said. "There is a growing body of research on declining fish production from Lake Tanganyika and other great lakes -- which coupled with the findings of this study, and the ever-increasing fishing pressure -- paint a gloomy future for the region. Therefore, sustainable fisheries of the lake can be achieved/maintained only if conventional fisheries management marries with ecosystem management and conservation approaches."

Co-author Sarah Ivory, with Penn State University, says the results make clear that changes in climate can have a cascading effect on the food webs in large tropical lakes.

"The impacts of this are akin to multi-year or multi-decade droughts in agricultural systems, from a food security perspective," she said.

Andrew Cohen, with the University of Arizona, says the findings have implications beyond tropical lakes as well.

"Climate impacts on freshwater resources in the tropics are a bellwether for global change worldwide," he said.

"This work is important, because climate changes that affect food security disproportionately hurt the poor," McGlue said. "This is one way science and social justice can become interwoven."

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The study, titled "Solar irradiance and ENSO affects food security in Lake Tanganyika, a major African inland fishery," can be read in full in Science Advances at https://advances.sciencemag.org/.

Additional co-authors include Jennifer Latimer with Indiana State University; Michael Soreghan with the University of Oklahoma; McKenzie Brannon, a UK alumna who contributed to the study during her time as an undergraduate; and Tumaini Kamulali, a University of Arizona graduate student and researcher from TAFIRI in Tanzania.

This research was supported by the UK-Pioneer Endowment, the Society of Exploration Geophysicists/Geoscientists Without Borders and the National Science Foundation.

NOTE TO REPORTERS: More information, including a copy of the paper, can be found online at the Science Advances press package at https://www.eurekalert.org/jrnls/sciadvances/.  You will need your user ID and password to access this information.

 

Most nations failing to protect nature in COVID-19 pandemic recovery plans

Outbreak provides opportunity to reset economy and reverse ecosystem, species losses

RUTGERS UNIVERSITY

Research News

IMAGE: THE FINANCIAL DISTRICT OF NEW YORK CITY AS SEEN FROM LIBERTY STATE PARK IN NEW JERSEY DURING THE COVID-19 PANDEMIC. view more 

CREDIT: PAMELA MCELWEE

The COVID-19 pandemic provides an opportunity to reset the global economy and reverse decades of ecosystem and species losses, but most countries are failing to invest in nature-related economic reforms or investments, according to a Rutgers-led paper.

Indeed, some countries, including the United States, Brazil and Australia, are back-tracking on existing laws and relaxing regulations and enforcement actions aimed at protecting nature, according to lead author Pamela McElwee, an associate professor in the Department of Human Ecology in the School of Environmental and Biological Sciences at Rutgers University-New Brunswick.

"Just last week at the United Nations, more than 60 heads of state spoke at a virtual summit and pledged their support to tackle the biodiversity crisis. But when we look at what countries are doing, either in their prior budget and policies or especially in their post-COVID planning and recovery packages, very few governments are putting their money where their mouths are," McElwee said. "We still see huge amounts of financial support for harmful practices, such as subsidizing overfishing or fossil fuel production or building infrastructure that will harm ecological integrity. Only a small number of countries are addressing the biodiversity crisis in the serious manner it deserves."

The paper, by economists, anthropologists and environmental scientists at many institutions on three continents, is published in the journal One Earth. It explores the changes in global economic systems - including incentives, regulations, fiscal policy and employment programs - that are necessary to shift away from activities that damage biodiversity and move toward those supporting ecosystem resilience.

Unless action is taken, around 1 million species face extinction, many within decades, and the global rate of species extinction will accelerate, according to the 2019 Global Assessment Report on Biodiversity and Ecosystem Services from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). That report noted the extinction rate is "already at least tens to hundreds of times higher than it has averaged over the past 10 million years." The authors of this new paper were all contributors to the 2019 IPBES report.

The new paper spells out the actions governments should be taking in their stimulus and recovery plans that would prioritize nature, provide immediate employment benefits and lead to longer-term transformations in the global economy. Examples include shifting from harmful fossil fuel subsidies to beneficial ones, including those that encourage environmentally friendly farming; carbon taxes that could support forest protection programs; and work programs that focus on ecological restoration and green infrastructure.

While many scientists and politicians have promoted a COVID-19 recovery that is low carbon, how to include biodiversity and ecosystems in economic plans has received much less attention. Discussions of nature-related actions have largely focused on closing wildlife markets as a potential source of novel viruses, expanding protected natural areas or reducing tropical deforestation. While these can be important, they do not necessarily address the root causes of ecological disruptions, the authors say.

A number of countries, including the United States and China, have allocated essentially zero stimulus funding to biodiversity or ecosystems. Only the European Union and member countries are making substantial financial investments in biodiversity for post-COVID planning. Other nations, including New Zealand, India and Pakistan, are proposing investments in nature-based jobs like ecological restoration, but at only modest levels.

"Governments are falling short of their stated promises and they need to do more - immediately," McElwee said. "We will continue to monitor proposed recovery packages, stimulus measures and financial pledges for how they address the biodiversity crises going forward, particularly in light of the mega-summit on biodiversity to be held in China next May."

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Droughts are threatening global wetlands: new study

UNIVERSITY OF ADELAIDE

Research News

 

IMAGE: ACIDIC (PH 4) AND IRON RICH (INDICATED BY ORANGE-BROWN COLOUR) WATER IN A WETLAND FOLLOWING EXPOSURE DURING DROUGHT view more 

CREDIT: LUKE MOSLEY

University of Adelaide scientists have shown how droughts are threatening the health of wetlands globally.

Published in the journal Earth-Science Reviews, the scientists highlight the many physical and chemical changes occurring during droughts that lead to severe, and sometimes irreversible, drying of wetland soils.

"Wetlands around the world are incredibly important for maintaining our planet's biodiversity and they store vast amounts of carbon that can help fight climate change," says project leader Associate Professor Luke Mosley, from the University's Environment Institute and School of Biological Sciences.

"Globally, wetlands cover an area greater than 12.1 million square kilometres and deliver at least A$37.8 trillion (Int$27 trillion) in benefits per year, such as for flood mitigation, food production, water quality improvement and carbon storage."

Wetlands can suffer "water droughts" both from the effects of a drier climate, and also when excessive water is extracted or diverted that would normally flow into them.

The review paper describes how drought often leads to severe cracking and compaction, acidification, loss of organic matter, and enhanced greenhouse gas (for example methane) emissions. In some cases droughts can lead to very long-term (>10 years) and irreversible soil changes, with major impacts on water quality when soils are rewet after the drought ends.

"We have seen many examples of how drought in the Murray-Darling Basin has caused major issues including acidification of soil and water due to acid sulfate soils exposure in wetlands. This review highlights substantial gaps in our global understanding of the effects of drought on wet soils and how they will respond to increasing drought," says Associate Professor Mosley, who is also Deputy Director of the Acid Sulfate Soils Centre.

Effects can be different in different soil types and different regions of the world. The spatial distribution of drought studies shows there has been limited assessment in a large number of regions, including south and central America, Africa, the Middle East, Asia and Oceania. Many of these regions are predicted to be vulnerable to drought impacts due to climate change.

Global distribution of wetland drought studies assessed in this review. Wetland distribution is in green and sites where drought studies were recorded and reviewed are marked as a 'x'. 

Lead author Dr Erinne Stirling, from Zhejiang University (China) and the University of Adelaide, says one of the most pressing findings from this review is that there are huge swaths of the world where there is no readily available published research on drought-affected wet soils.

And secondly, she says, there is effectively no applied research into water management outcomes for wetlands and wetland soils.

"At a global level, wet soils are highly vulnerable to the effects of climate change and need to be protected given the very high environmental and socio-economic values they support. It is our sincere hope that the information in this review contributes to protecting these valuable ecosystems," says Dr Stirling.

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Media Contact:

Associate Professor Luke Mosley, School of Biological Sciences, University of Adelaide. Phone: +61 (0)8 8313 5453. Mobile: +61 (0)428 103 563, luke.mosley@adelaide.edu.au

Robyn Mills, Senior Media and Communications Officer. University of Adelaide. Phone: +61 (0)8 8313 6341, Mobile: +61 (0)410 689 084, robyn.mills@adelaide.edu.au

 

Scientists suggest global guidelines for sustainable use of non-native trees

A team of international scientists have collaborated to propose a series of global guidelines for the sustainable use of non-native tree species to help protect biodiversity and ecosystems around the world already threatened by climate change

CABI

Research News

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IMAGE: PINUS PINASTER, ONE OF MANY NON-NATIVE TREES THAT IS HIGHLY INVASIVE AND CAUSES MAJOR IMPACTS IN SOUTH AFRICA. THE IMAGE SHOWS A DENSE INVASIVE STAND OF PINES IN THE MOUNTAINS... view more 

CREDIT: DAVE RICHARDSON

A team of international scientists have collaborated to propose a series of global guidelines for the sustainable use of non-native tree species to help protect biodiversity and ecosystems around the world already threatened by climate change.

The new paper, published today in the journal NeoBiota, uses the Council of Europe - Bern Convention Code of Conduct on Invasive Alien Trees as a starting point, to present eight recommendations all aimed at maximising the benefits of non-native trees, while minimising their negative impacts.

The guidelines include using native trees, or non-invasive non-native trees as opposed to invasive non-native trees, being aware of the risk of invasion and consider global change trends and developing and supporting global networks and collaborative research and information sharing on native and non-native trees.

The scientists suggest that the guidelines are a first step towards building a global agreement on the precautions that should be taken when introducing and planting non-native trees and serve to complement statutory requirements under international and national legislation.

Lead author Dr Giuseppe Brundu, from the University of Sassari, Italy, said, "The application of the global guidelines and the achievement of their goals will help to conserve forest biodiversity, ensure sustainable forestry, and contribute to the achievement of several Sustainable Development Goals (SDGs) of the United Nations linked with forest biodiversity."

The researchers highlight how non-native species - such as Prosopis juliflora which was introduced in Eastern Africa in the 1970s to provide wood and fodder for livestock and help reduce soil erosion and the effects of dust storms - make up 44% of plantation forests globally.

They point to major tree planting campaigns, including the 60 Million Trees Initiative from the Madagascar Government, which either do not specify or include non-native species planted - often to balance economic and ecological interests as with the case in Madagascar. Other similar schemes have included 60 million trees planted in Italy - one for each Italian citizen to fight climate change - where a mix of native and non-native tree species were recommended.

However, the scientists warn that unless their global guidelines are taken seriously the spread of non-native tree species will make the conservation of forest biodiversity and work towards achieving a number of SDGs - linked with forest sustainability - difficult to achieve.

Professor Dave Richardson, co-author from Stellenbosch University, South Africa, said, "The global guidelines on non-native tree species offer general recommendations and provide a basic framework and suggestions on tools for planning and implementing sustainable use of non-native trees in nationally appropriate and scientifically sound practices that account for national and sub-national needs."

Dr Urs Schaffner, co-author and Head Ecosystems Management at CABI Switzerland, is an expert on Prosopis juliflora and believes such invasive trees can also impact severely on rural people's livelihoods with, for example, 86% losses in grassland experienced in Baringo Country, Kenya.

Dr Schaffner added, "It is important to bear in mind that national circumstances vary considerably in terms of biophysical conditions, institutional and legal frameworks, economic challenges and possibilities, management, and use, among other factors.

"Therefore, no 'one-size-fits-all' approach can be applied in the implementation of the guidelines. Instead, various technical and organisational options must be combined to achieve efficient implementation of the guidelines."

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Additional information

Main image: Pinus pinaster, one of many non-native trees that is highly invasive and causes major impacts in South Africa. The image shows a dense invasive stand of pines in the mountains of the Western Cape (Credit: Dave Richardson).

Full paper reference

Brundu G, Pauchard A, Pyšek P, Perg J, Bindewald AM, Brunori A, Canavan S, Campagnaro T, Celesti-Grapow L, Dechoum M de S, Dufour-Dror J-M, Essl F, Flory LS, Genovesi P, Guarino F, Guangzhe L, Hulme PE, Jäger H, Kettle CJ, Krumm F, Langdon B, Lapin K, Lozano V, Le Roux JJ, Novoa A, Nuñez MA, Porté AJ, Silva JS, Schaffner U, Sitzia T, Tanner R, Tshidada N, Vítková M, Westergren M, Wilson JRU, Richardson DM, 'Global guidelines for the sustainable use of non-native trees to prevent tree invasions and mitigate their negative impacts,' NeoBiota, DATE IN HERE,2020. DOI: 10.3897/neobiota.61.58380.

The paper is available to view open access from here: https://neobiota.pensoft.net/article/58380/

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Geologists solve puzzle that could predict valuable rare earth element deposits

UNIVERSITY OF EXETER

Research News

 

IMAGE: PIONEERING NEW RESEARCH HAS HELPED GEOLOGISTS SOLVE A LONG-STANDING PUZZLE THAT COULD HELP PINPOINT NEW, UNTAPPED CONCENTRATIONS OF SOME THE MOST VALUABLE RARE EARTH DEPOSITS. view more 

CREDIT: MICHAEL ANENBURG, ANU.

Pioneering new research has helped geologists solve a long-standing puzzle that could help pinpoint new, untapped concentrations of some the most valuable rare earth deposits.

A team of geologists, led by Professor Frances Wall from the Camborne School of Mines, have discovered a new hypothesis to predict where rare earth elements neodymium and dysprosium could be found.

The elements are among the most sought after, because they are an essential part of digital and clean energy manufacturing, including magnets in large wind turbines and electric cars motors.

For the new research, scientists conducted a series of experiments that showed sodium and potassium - rather than chlorine or fluorine as previously thought - were the key ingredients for making these rare earth elements soluble.

This is crucial as it determines whether they crystalise - making them fit for extraction - or stayed dissolved in fluids.

The experiments could therefore allow geologists to make better predictions about where the best concentrations of neodymium and dysprosium are likely to be found.

The results are published in the journal, Science Advances on Friday, October 9th 2020.

University of Exeter researchers, through the 'SoS RARE' project, have previously studied many natural examples of the roots of very unusual extinct carbonatite volcanoes, where the world's best rare earth deposits occur, in order to try and identify potential deposits of the rare earth minerals.

However, in order to gain a greater insight into their results, they invited Michael Anenburg to join the team to carry out experiments at the Australian National University (ANU).

He simulated the crystallisation of molten carbonate magma to find out which elements would be concentrated in the hot waters left over from the crystallisation process.

It showed that sodium and potassium make the rare earths soluble in solution. Without sodium and potassium, rare earth minerals precipitate in the carbonatite itself. With sodium, intermediate minerals like burbankite form and are then replaced. With potassium, dysprosium is more soluble than neodymium and carried out to the surrounding rocks.

Professor Frances Wall, leader of the SoS RARE project said: "This is an elegant solution that helps us understand better where 'heavy' rare earths like dysprosium and 'light' rare earths like neodymium' may be concentrated in and around carbonatite intrusions. We were always looking for evidence of chloride-bearing solutions but failing to find it. These results give us new ideas."

Michael Anenburg , a Postdoctoral Fellow at ANU said: "My tiny experimental capsules revealed minerals that nature typically hides from us. It was a surprise how well they explain what we see in natural rocks and ore deposits."

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Rare earth element mobility in and around carbonatites controlled by sodium, potassium, and silica is published in Science Advances on Friday, October 9th 2020.

The SoS RARE project was funded by the Natural Environment Research Council (UK Research and Innovation) as part of its Security of Supply of Minerals programme to help secure diverse and sustainable supplies of 'e-tech' metals such as the rare earths.

http://www.sosrare.org

www2.bgs.ac.uk/sosMinerals

 

Spitzer space telescope legacy chronicled in Nature Astronomy

UNIVERSITY OF CENTRAL FLORIDA

Research News

 

IMAGE: UCF PLANETARY SCIENTIST NOEMÍ PINILLA-ALONSO IS EAGER TO SEE THE JAMES WEBB SPACE TELESCOPE LAUNCH TO SEE WHAT OTHER WONDERS AWAIT US. view more 

CREDIT: UNIVERSITY OF CENTRAL FLORIDA

To understand the significance of the Spitzer Space Telescope on the understanding of our solar system, think of what the steam engine meant for the industrial revolution.

A national team of scientists today published in the journal Nature Astronomy two papers that provide an inventory of the major discoveries made possible thanks to Spitzer and offer guidance on where the next generation of explorers should point the James Webb Space Telescope (JWST) when it launches in October 2021.

"The Spitzer Space Telescope made many important discoveries in the solar system during its 16 year-long mission, and it is important to capture the highlights of these with useful references for future scientists to use in their research," says Carey M. Lisse, from the Johns Hopkins Applied Physics Lab, lead author of one paper.

Lisse, a planetary astronomer, put together the team of 27 authors who penned the legacy papers. The authors were selected based on the significant discoveries they made using Spitzer during its 16-year mission. The team includes three University of Central Florida researchers, who offer suggestions for the next space telescope mission.

David Trilling, a planetary scientist and professor at Northern Arizona University, is the lead author on the second paper.

When Spitzer launched in 2003 it contained infrared detectors of unprecedented sensitivity, providing astronomers a never-before-possible look at the universe. Thanks to observations by Spitzer over the years, scientists gained new insights into, for example, the composition of comets, the icy surfaces of cold, distant bodies beyond Neptune, the heat radiation given off by asteroids, the extent of free-floating dust in the inner solar system, and the composition and properties of the atmospheres of Uranus and Neptune. Spitzer even managed to discover a new ring of Saturn! The much-delayed JWST, which will likewise study the infrared cosmos, is expected to build on the extensive results provided by Spitzer, including taking the next step in our study of the solar system.

UCF Professor Yan Fernandez, who specializes in comets, said the papers include some of the projects he is most proud off in his career. Fernandez is a co-author on both papers.

"I think these papers demonstrate the return on investment for Spitzer," Fernandez said. "These space telescopes are taxpayer-funded, after all. More philosophically, Spitzer has brought us closer to those big questions about why the solar system and Earth are here in the first place. Spitzer was not only great for the solar system, but it was great for studying exoplanets, great for studying planet formation, and great for studying star formation. All important to understand why our solar system turned out the way it did."

Noemí Pinilla-Alonso said astronomy is based on patience and collaboration. She studies Trans-Neptunian Objects at UCF's Florida Space Institute and contributed to the paper alongside institute post-doctoral scholar Estela Fernández-Valenzuela. Pinilla-Alonso is among a handful of scientists already guaranteed time on JWST once it is place. She is part of the team that will be calibrating the instrument from the ground.

"Answering one question takes the effort of multiple scientists or groups, each of them with a unique set of skills," Pinilla-Alonso says. "My contribution to this work is to provide the basic recipe of which ingredients are needed to build or cook an icy body in the solar system. And this is a key piece of information that is needed to answer questions such as how did the solar system form? How has it evolved to its actual state? How similar or different is our solar system from the long list, more than 3,000, of exoplanetary systems discovered?"

Fernandez-Valenzuela also studies Trans-Neptunian Objects and earlier this year held workshops to help scientists prepare successful proposals to obtain time on the JWST once NASA opens up the process.

"This work has helped us to understand what we could do with Spitzer data and how to use the JWST capabilities to shed light on issues that Spitzer could not answer," Fernández-Valenzuela says.

"Using Spitzer we have been able to detect specific materials that were impossible to detect from ground-based telescopes, due to the atmosphere, or using the Hubble Space Telescope," Fernández-Valenzuela says. "Now with JWST we will be able to obtain information on much fainter objects than is currently possible. I'm eager for that day as it will be a very important milestone for this research area. It will provide much more information on the formation of the outer solar system."

Spitzer was turned off in January 2020, 11 years beyond its prime mission.

"Spitzer was sensitive to infrared radiation, as opposed to visible light," Trilling says. "In many ways, Spitzer provided a view of the universe and of planetary bodies in our solar system that scientists had never seen before. This technological revolution produced new insights into the formation and evolution of our Solar System."

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Future ocean conditions could cause significant physical changes in marine mussels

UNIVERSITY OF PLYMOUTH

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IMAGE: MARINE MUSSELS ARE COMMONLY USED TO MONITOR WATER QUALITY IN COASTAL AREAS view more 

CREDIT: UNIVERSITY OF PLYMOUTH

The increased temperature and acidification of our oceans over the next century have been argued to cause significant physical changes in an economically important marine species.

Scientists from the University of Plymouth exposed blue mussels (Mytilus edulis) to current and future levels of ocean acidification (OA) or warming (W), as well as both together - commonly known as OAW.

Initial comparison of mussel shells showed that warming alone led to increased shell growth, but increasing warming and acidification led to decreased shell growth indicating that OA was dissolving their shells.

However, analysis using cutting edge electron microscopy of the shell crystal matrix or 'ultrastructure' revealed that, in fact, warming alone has the potential to significantly alter the physical properties of the mussels' shells, whereas acidification mitigated some of the negative effects.

Mussels grown under warming exhibited changes in their crystal structures including a propensity for increased brittleness, which would place mussels under greater threat from their many predators including crabs and starfish.

These negative effects were to some degree mitigated under acidified conditions with mussel shells showing evidence of repair, even though their crystals grew differently to the norm.

The study, published in a Frontiers of Marine Science special issue titled Global Change and the Future Ocean, is the latest research by the University into the potential effects of ocean warming and acidification on marine species.

Previous projects have suggested future conditions could significantly reduce the nutritional qualities of oysters as well as dissolving the shells of sea snails and reducing their overall size by around a third.

Dr Antony Knights, Associate Professor in Marine Ecology and the study's lead author, said: "By the end of the century, we are predicted to see increases in sea surface temperature of 2-4°C and at least a doubling of atmospheric CO2. It is no surprise that would have an effect on marine species, but this research is surprising in that acidification appears to mitigate changes in shell structure attributable to rising sea temperatures, which is counter to what we would have predicted. It may be that increased CO2 in the water is providing more 'raw material' for the mussels to repair their shells that is not available under just warming conditions."

Dr Natasha Stephen, Director of Plymouth Electron Microscopy Centre, added: "Until now, there have been relatively few studies assessing the combined effects of ocean acidification and warming on shell structures. However, understanding the changes that might result at a microscopic level may provide important insights in to how organisms will respond to future climate change. This study shows it can certainly have negative effects but also that they are not always predictable, which presents some serious challenges when it comes to trying to disentangle the consequences of climate change."

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Ice melt projections may underestimate Antarctic contribution to sea level rise

PENN STATE

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IMAGE: THWAITES GLACIER, ANTARCTICA, PICTURED IN 2019. view more 

CREDIT: NASA

Fluctuations in the weather can have a significant impact on melting Antarctic ice, and models that do not include this factor can underestimate the global impact of sea level rise, according to Penn State scientists.

"We know ice sheets are melting as global temperatures increase, but uncertainties remain about how much and how fast that will happen," said Chris Forest, professor of climate dynamics at Penn State. "Our findings shed new light on one area of uncertainty, suggesting climate variability has a significant impact on melting ice sheets and sea level rise."

While it is understood that continued warming may cause rapid ice loss, models that predict how Antarctica will respond to climate change have not included the potential impacts of internal climate variability, like yearly and decadal fluctuations in the climate, the team of scientists said.

Accounting for climate variability caused models to predict an additional 2.7 to 4.3 inches -- 7 to 11 centimeters -- of sea level rise by 2100, the scientists recently reported in the journal Climate Dynamics. The models projected roughly 10.6 to 14.9 inches -- 27 to 38 centimeters -- of sea level rise during that same period without climate variability.

"That increase alone is comparable to the amount of sea level rise we have seen over the last few decades," said Forest, who has appointments in the departments of meteorology and atmospheric science and geosciences. "Every bit adds on to the storm surge, which we expect to see during hurricanes and other severe weather events, and the results can be devastating."

The Antarctic ice sheet is a complex system, and modeling how it will evolve under future climate conditions requires thousands of simulations and large amounts of computing power. Because of this, modelers test how the ice will respond using a mean temperature found by averaging the results of climate models.

However, that process smooths out peaks caused by climate variability and reduces the average number of days above temperature thresholds that can impact the ice sheet melt, creating a bias in the results, the scientists said.

"If we include variability in the simulations, we are going to have more warm days and more sunshine, and therefore when the daily temperature gets above a certain threshold it will melt the ice," Forest said. "If we're just running with average conditions, we're not seeing these extremes happening on yearly or decadal timescales."

To study the effects of internal climate variability, the researchers analyzed two large ensembles of climate simulations. Large ensembles are generated by starting each member with slightly different initial conditions. The chaotic nature of the climate system causes each member to yield slightly different responses, and this represents internally generated variability, the scientists said.

Instead of averaging the results of each ensemble, the scientists fed the atmospheric and oceanic data representing this variability into a three-dimensional Antarctic ice sheet model. They found atmospheric variations had a larger and more immediate impact on the ice sheet, but ocean variability was also a significant factor.

Extensive parts of the ice sheet are in contact with ocean water, and previous studies have suggested that warming oceans could cause large chunks to break away. The process may expose ice cliffs so tall that they collapse under their own weight, inducing a domino effect that further depletes the ice shelf.

The scientists found model simulations that did not include the effects of internal climate variability significantly delayed the retreat of the ice sheet by up to 20 years and underestimated future sea level rise.

"This additional ice melt will impact the hurricane storm surges across the globe. Additionally, for years, the IPCC reports have been looking at sea level rise without considering this additional variability and have been underestimating what the impact may be," Forest said. "It's important to better understand these processes contributing to the additional ice loss because the ice sheets are melting much faster than we expected."

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Also participating from Penn State were David Pollard, research professor in the Earth and Environmental Systems Institute, and Chii-Yun Tsai, a former doctoral student.

The National Science Foundation and the Penn State Center for Climate Risk Management funded this research.

 

Climate patterns linked in Amazon, North and South America, study shows

A tree-ring chronology developed by U of A researchers established a connection between precipitation in the Amazon and the Americas

UNIVERSITY OF ARKANSAS

Research News

 

IMAGE: DAVID STAHLE, DISTINGUISHED PROFESSOR OF GEOSCIENCES, AT THE UNIVERSITY OF ARKANSAS TREE RING LABORATORY view more 

CREDIT: RUSSELL COTHREN

FAYETTEVILLE, Ark. -University of Arkansas researchers have established a link between climate patterns in the Amazon and large parts of North and South America using their newly developed tree-ring chronology from the Amazon River basin.

The discovery helps researchers better understand large-scale climate extremes and the impact of the El Niño phenomenon.

Tree growth is a well-established climate proxy. By comparing growth rings in Cedrela odorata trees found in the Rio Paru watershed of the eastern Amazon River with hundreds of similar chronologies in North and South America, scientists have shown an inverse relationship in tree growth, and therefore precipitation patterns, between the areas. Drought in the Amazon is correlated with wetness in the southwestern United States, Mexico and Patagonia, and vice versa.

The process is driven by the El Niño phenomenon, which influences surface-level winds along the equator, researchers said. El Niño is the name given to a large-scale irregularly occurring climate pattern associated with unusually warm water in the Pacific Ocean.

"The new Cedrela chronologies from the Amazon, when compared with the hundreds of tree-ring chronologies in temperate North and South America, document this Pan American resonance of climate and ecosystem extremes in the centuries before widespread deforestation or human-caused climate change," said Dave Stahle, Distinguished Professor of geosciences and first author of a study documenting the findings in the journal Environmental Research Letters.

The connection was not documented until researchers at the University of Arkansas Tree Ring Laboratory, along with colleagues from Brazil and Argentina, developed rainfall reconstructions from growth rings in Cedrela trees. Most rainfall records in the Amazon only date back about 70 years, but Cedrelas live for 200 to 300 years, providing valuable rainfall proxies that pre-date human-influenced climate change. Their work in the Amazon is documented in a short video, and also on a dedicated web site.

In the past 40 years, drought and flood extremes have increased in the Amazon basin, the researchers noted, raising the question of whether human-induced climate change and deforestation are affecting Amazon climate. While that remains an open question, the longer Cedrela-based precipitation record indicates that periods of rainfall extremes occurred in the past and the current extremes might be partly due to natural climate rhythms.

The study will help researchers better understand an area of unequaled biodiversity. The Amazon is home to an estimated 16,000 species of trees and one-tenth of all known species found on the planet, Stahle noted. "The long climate history written in the growth rings of old Cedrela trees in Amazonia will surely be important to the sustainability of the biome."