Unregulated, agricultural ammonia threatens U.S. national parks’ ecology

Oct. 10, 2013 — Thirty-eight U.S. national parks are experiencing “accidental fertilization” at or above a critical threshold for ecological damage, according to a study published in the journal Atmospheric Chemistry and Physicsand led by Harvard University researchers. Unless significant controls on ammonia emissions are introduced at a national level, they say, little improvement is likely between now and 2050.The environmental scientists, experts in air quality, atmospheric chemistry, and ecology, have been studying the fate of nitrogen-based compounds that are blown into natural areas from power plants, automobile exhaust, and — increasingly — industrial agriculture. Nitrogen that finds its way into natural ecosystems can disrupt the cycling of nutrients in soil, promote algal overgrowth and lower the pH of water in aquatic environments, and ultimately decrease the number of species that can survive.”The vast majority, 85 percent, of nitrogen deposition originates with human activities,” explains principal investigator Daniel J. Jacob, Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering at the Harvard School of Engineering and Applied Sciences (SEAS). “It is fully within our power as a nation to reduce our impact.”Existing air quality regulations and trends in clean energy technology are expected to reduce the amount of harmful nitrogen oxides (NOx) emitted by coal plants and cars over time. However, no government regulations currently limit the amount of ammonia (NH3) that enters the atmosphere through agricultural fertilization or manure from animal husbandry, which are now responsible for one-third of the anthropogenic nitrogen carried on air currents and deposited on land.”Ammonia’s pretty volatile,” says Jacob. “When we apply fertilizer in the United States, only about 10 percent of the nitrogen makes it into the food. All the rest escapes, and most of it escapes through the atmosphere.”The team of scientists — comprising researchers from Harvard SEAS, the National Park Service, the USDA Forest Service, the U.S. …

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Creating plants that make their own fertilizer

Aug. 24, 2013 — Since the dawn of agriculture, people have exercised great ingenuity to pump more nitrogen into crop fields. Farmers have planted legumes and plowed the entire crop under, strewn night soil or manure on the fields, shipped in bat dung from islands in the Pacific or saltpeter from Chilean mines and plowed in glistening granules of synthetic fertilizer made in chemical plants.No wonder biologist Himadri Pakrasi’s team is excited by the project they are undertaking. If they succeed, the chemical apparatus for nitrogen fixation will be miniaturized, automated and relocated within the plant so nitrogen is available when and where it is needed — and only then and there.”That would really revolutionize agriculture,” said Pakrasi, PhD, the Myron and Sonya Glassberg/Albert and Blanche Greensfelder Distinguished University Professor in Arts & Sciences and director of the International Center for Advanced Renewable Energy and Sustainability (I-CARES) at Washington University in St. Louis.Engineering with biological partsAlthough there is plenty of nitrogen in the atmosphere, atmospheric nitrogen is not in a form plants can use. Atmospheric nitrogen must be “fixed,” or converted into compounds that make the nitrogen available to plants.Much of modern agriculture relies on biologically available nitrogenous compounds made by an industrial process, developed by German chemist Fritz Haber in 1909. The importance of the Haber-Bosch process, as it eventually was called, can hardly be overstated; today, the fertilizer it produces allows us to feed a population roughly a third larger than the planet could sustain without synthetic fertilizer.On the other hand, the Haber-Bosch process is energy-intensive, and the reactive nitrogen released into the atmosphere and water as runoff from agricultural fields causes a host of problems, including respiratory illness, cancer and cardiac disease.Pakrasi thinks it should be possible to design a better nitrogen-fixing system. His idea is to put the apparatus for fixing nitrogen into plant cells, the same cells that hold the apparatus for capturing the energy in sunlight.The National Science Foundation just awarded Pakrasi and his team more than $3.87 million to explore this idea further. The grant will be administered out of I-CARES, a university-wide center that supports collaborative research regionally, nationally, and internationally in the areas of energy, the environment and sustainability.This award is one of four funded by the National Science Foundation jointly with awards funded by the Biotechnology and Biological Sciences Research Council in the United Kingdom. The teams will collaborate with one another and meet regularly to share progress and successes.A proof of principleAs a proof of principle, Pakrasi and his colleagues plan to develop the synthetic biology tools needed to excise the nitrogen fixation system in one species of cyanobacterium (a phylum of green bacteria formerly considered to be algae) and paste it into a second cyanobacterium that does not fix nitrogen.The team includes: Tae Seok Moon, PhD, and Fuzhong Zhang, PhD, both assistant professors of energy, environmental and chemical engineering in the School of Engineering & Applied Science at Washington University; and Costas D. …

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World-changing technology enables crops to take nitrogen from the air

July 25, 2013 — A major new technology has been developed by The University of Nottingham, which enables all of the world’s crops to take nitrogen from the air rather than expensive and environmentally damaging fertilisers.Nitrogen fixation, the process by which nitrogen is converted to ammonia, is vital for plants to survive and grow. However, only a very small number of plants, most notably legumes (such as peas, beans and lentils) have the ability to fix nitrogen from the atmosphere with the help of nitrogen fixing bacteria. The vast majority of plants have to obtain nitrogen from the soil, and for most crops currently being grown across the world, this also means a reliance on synthetic nitrogen fertiliser.Professor Edward Cocking, Director of The University of Nottingham’s Centre for Crop Nitrogen Fixation, has developed a unique method of putting nitrogen-fixing bacteria into the cells of plant roots. His major breakthrough came when he found a specific strain of nitrogen-fixing bacteria in sugar-cane which he discovered could intracellularly colonise all major crop plants. This ground-breaking development potentially provides every cell in the plant with the ability to fix atmospheric nitrogen. The implications for agriculture are enormous as this new technology can provide much of the plant’s nitrogen needs.A leading world expert in nitrogen and plant science, Professor Cocking has long recognised that there is a critical need to reduce nitrogen pollution caused by nitrogen based fertilisers. Nitrate pollution is a major problem as is also the pollution of the atmosphere by ammonia and oxides of nitrogen.In addition, nitrate pollution is a health hazard and also causes oxygen-depleted ‘dead zones’ in our waterways and oceans. A recent study estimates that that the annual cost of damage caused by nitrogen pollution across Europe is £60 billion — £280 billion a year.Speaking about the technology, which is known as ‘N-Fix’, Professor Cocking said: “Helping plants to naturally obtain the nitrogen they need is a key aspect of World Food Security. The world needs to unhook itself from its ever increasing reliance on synthetic nitrogen fertilisers produced from fossil fuels with its high economic costs, its pollution of the environment and its high energy costs.” N-Fix is neither genetic modification nor bio-engineering. It is a naturally occurring nitrogen fixing bacteria which takes up and uses nitrogen from the air. …

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Declines in ecosystem productivity fueled by nitrogen-induced species loss

July 3, 2013 — Humans have been affecting their environment since the ancestors of Homo sapiens first walked upright, but never has their impact been more detrimental than in the 21st century. “The loss of biodiversity has much greater and more profound ecosystem impacts than had ever been imagined,” said David Tilman, professor of ecology, biodiversity and ecosystem functioning at UC Santa Barbara’s Bren School of Environmental Science & Management.Human-driven environmental disturbances, such as increasing levels of reactive nitrogen and carbon dioxide (CO2), have multiple effects, including changes in biodiversity, species composition, and ecosystem functioning. Pieces of this puzzle have been widely examined but this new study puts it all together by examining multiple elements. The results were published July 1 in the Proceedings of the National Academy of Sciences.According to the team’s recent findings, adding nitrogen to grasslands led to an initial increase in ecosystem productivity. However, that increase proved unsustainable because the increased nitrogen resulted in a loss of plant diversity. “In combination with earlier studies, our results show that the loss of biodiversity, no matter what might cause it, is a major driver of ecosystem functioning,” said Tilman.The study analyzed 30 years of field data from the Nitrogen Enrichment Experiment in order to determine the temporal effect of nitrogen enrichment on the productivity, plant diversity, and species composition of naturally assembled grasslands at the Cedar Creek Ecosystem Science Reserve in central Minnesota. The results showed that while nitrogen enrichment initially increased plant productivity, eventually this effect declined, especially in the plots that received the most fertilizer. These returns diminished over time because fertilizing also drove declines in plant diversity.In fact, the continuous addition of nitrogen fertilizer led to a loss of the dominant native perennial grass, Schizachyrium scoparium, which decreased productivity twice as much as did random species loss in a nearby biodiversity experiment. In contrast, elevated CO2 didn’t decrease or change grassland plant diversity in any way and consistently promoted productivity over time.According to the authors, previous studies have underestimated the impact of biodiversity on ecosystem functioning. “Many people expect that only rare or subordinate species will be lost and that their loss will have negligible effects on ecosystem functioning,” says lead author Forest Isbell, a postdoctoral associate in the Department of Ecology, Evolution & Behavior at the University of Minnesota in Saint Paul. …

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Study of oceans’ past raises worries about their future

June 14, 2013 — The ocean the Titanic sailed through just over 100 years ago was very different from the one we swim in today. Global warming is increasing ocean temperatures and harming marine food webs. Nitrogen run-off from fertilizers is causing coastal dead zones. A McGill-led international research team has now completed the first global study of changes that occurred in a crucial component of ocean chemistry, the nitrogen cycle, at the end of the last ice age. The results of their study confirm that oceans are good at balancing the nitrogen cycle on a global scale. But the data also shows that it is a slow process that may take many centuries, or even millennia, raising worries about the effects of the scale and speed of current changes in the ocean.”For the first time we can quantify how oceans responded to slow, natural climate warming as the world emerged from the last ice age,” says Prof. Eric Galbraith from McGill University’s Department of Earth and Oceanic Sciences, who led the study. “And what is clear is that there is a strong climate sensitivity in the ocean nitrogen cycle.”The nitrogen cycle is a key component of the global ocean metabolism. Like the proteins that are essential to human health, nitrogen is crucial to the health of oceans. And just as proteins are carried by the blood and circulate through the body, the nitrogen in the ocean is kept in balance by marine bacteria through a complicated cycle that keeps the ocean healthy. …

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Acceleration of ocean denitrification during deglaciation documented

June 3, 2013 — As ice sheets melted during the deglaciation of the last ice age and global oceans warmed, oceanic oxygen levels decreased and “denitrification” accelerated by 30 to 120 percent, a new international study shows, creating oxygen-poor marine regions and throwing the oceanic nitrogen cycle off balance.By the end of the deglaciation, however, the oceans had adjusted to their new warmer state and the nitrogen cycle had stabilized — though it took several millennia. Recent increases in global warming, thought to be caused by human activities, are raising concerns that denitrification may adversely affect marine environments over the next few hundred years, with potentially significant effects on ocean food webs.Results of the study have been published this week in the journal Nature Geoscience.”The warming that occurred during deglaciation some 20,000 to 10,000 years ago led to a reduction of oxygen gas dissolved in sea water and more denitrification, or removal of nitrogen nutrients from the ocean,” explained Andreas Schmittner, an Oregon State University oceanographer and author on the Nature Geoscience paper. “Since nitrogen nutrients are needed by algae to grow, this affects phytoplankton growth and productivity, and may also affect atmospheric carbon dioxide concentrations.””This study shows just what happened in the past, and suggests that decreases in oceanic oxygen that will likely take place under future global warming scenarios could mean more denitrification and fewer nutrients available for phytoplankton,” Schmittner added.In their study, the scientists analyzed more than 2,300 seafloor core samples, and created 76 time series of nitrogen isotopes in those sediments spanning the past 30,000 years. They discovered that during the last glacial maximum, the Earth’s nitrogen cycle was at a near steady state. In other words, the amount of nitrogen nutrients added to the oceans — known as nitrogen fixation — was sufficient to compensate for the amount lost by denitrification.A lack of nitrogen can essentially starve a marine ecosystem by not providing enough nutrients. Conversely, too much nitrogen can create an excess of plant growth that eventually decays and uses up the oxygen dissolved in sea water, suffocating fish and other marine organisms.Following the period of enhanced denitrification and nitrogen loss during deglaciation, the world’s oceans slowly moved back toward a state of near stabilization. But there are signs that recent rates of global warming may be pushing the nitrogen cycle out of balance.”Measurements show that oxygen is already decreasing in the ocean,” Schmittner said “The changes we saw during deglaciation of the last ice age happened over thousands of years. But current warming trends are happening at a much faster rate than in the past, which almost certainly will cause oceanic changes to occur more rapidly.”It still may take decades, even centuries to unfold,” he added.Schmittner and Christopher Somes, a former graduate student in the OSU College of Earth, Ocean, and Atmospheric Sciences, developed a model of nitrogen isotope cycling in the ocean, and compared that with the nitrogen measurements from the seafloor sediments. Their sensitivity experiments with the model helped to interpret the complex patterns seen in the observations.This study was supported by the National Science Foundation.

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Microbes capture, store, and release nitrogen to feed reef-building coral

May 14, 2013 — Microscopic algae that live within reef-forming corals scoop up available nitrogen, store the excess in crystal form, and slowly feed it to the coral as needed, according to a study published in mBio®, the online open-access journal of the American Society for Microbiology. Scientists have known for years that these symbiotic microorganisms serve up nitrogen to their coral hosts, but this new study sheds light on the dynamics of the process and reveals that the algae have the ability to store excess nitrogen, a capability that could help corals cope in their chronically low-nitrogen environment.

“It was a great surprise to find the nitrogen-rich crystals inside the algae,” says corresponding author Anders Meibom of the École Polytechnique Fédérale de Lausanne, Switzerland. “It all makes perfect sense now. The algae suck up the ammonium and nitrate like a sponge when the concentration of these molecules increases, then store this nitrogen as uric acid crystals for later use.”

Like all reef-forming corals, the species they studied, Pocillopora damicornis, is actually a symbiosis of two different organisms: the coral provides protection to a species of photosynthetic algae called dinoflagellates, which, in turn, provide sugars and nitrogen to the coral host. The symbiosis allows the coral to thrive in clear, tropical waters that are naturally nutrient-poor. In many places, however, coral reefs are suffering from an excess of nutrients – pollution from sewage and fertilizers that impacts the symbiotic relationship and the health of coral in unknown ways.

To better understand these exchanges of materials and to determine how an excess of nutrients might affect the balance, the researchers exposed pieces of coral to varying concentrations of isotopically-labeled nitrogen-rich compounds. Using the facilities at the Aquarium Tropicale Porte Dorée in Paris, France, the scientists applied a relatively new analytic technique called nano-scale secondary ion mass-spectrometry (NanoSIMS) to follow the path of the nitrogen. NanoSIMS enabled them to visualize and quantify the uptake, movement, and accumulation of this labeled nitrogen within the coral.

When supplied with nitrogen in the form of ammonium, nitrate or aspartic acid the dinoflagellates responded by rapidly storing the nitrogen as crystals of uric acid within its cells. But the dinoflagellates don’t hang onto the nitrogen for long. Starting at about six hours after exposure, the microbes begin translocating nitrogen-rich compounds to the coral host, where the nitrogen is used in specific cellular compartments all over the surface layers of the coral.

This storage and release process helps explain how these corals get through the ups and downs of nitrogen concentrations, says Meibom. “This gives the coral-algae symbiosis a very efficient way to deal with strong fluctuations in nitrogen availability,” writes Meibom. “When the nitrogen availability suddenly becomes high, the algae can take-up large amounts of nitrogen on a timescale of a few hours, store it into crystals inside the algae cells and then release this stored nitrogen for metabolic processes and growth when the nitrogen levels become normal again.”

To follow up on this work, Meibom says he and his colleagues are now studying how carbon-based nutrients are taken up and distributed in the same coral-algae symbiosis.

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