FROM: NATIONAL SCIENCE FOUNDATION
Revealing the ocean's hidden fertilizer
Tiny marine plants play major role in phosphorus cycle
Phosphorus is one of the most common substances on Earth.
An essential nutrient for every living organism--humans require approximately 700 milligrams per day--we're rarely concerned about consuming enough because it is in most of the foods we eat.
Despite its ubiquity and living organisms' dependence on it, we know surprisingly little about how it moves, or cycles, through the ocean environment.
Scientists studying the marine phosphorous cycle have known that phosphorus was absorbed by plants and animals and released back to seawater in the form of phosphate as these plants and animals decay and die.
But a growing body of research hints that microbes in the ocean transform phosphorus in ways that remain a mystery.
Hidden role of ocean's microbes
A new study by a research team from the Woods Hole Oceanographic Institution (WHOI) and Columbia University reveals for the first time a marine phosphorus cycle that is much more complex than previously thought.
The work also highlights the important but previously hidden role that some microbial communities play in using and breaking down forms of this essential element.
A paper reporting the findings is published this week in the journal Science.
"A reason to be excited about this elegant study is in the paper's last sentence: 'the environmental, ecological and evolutionary controls ...remain completely unknown,'" says Don Rice, program director in the National Science Foundation's (NSF) Division of Ocean Sciences, which funded the research through its Chemical Oceanography Program. "There's still a lot we don't know about the sea."
The work is also supported by an NSF Dimensions of Biodiversity grant.
"This is an exciting new discovery that closes a fundamental knowledge gap in our understanding of the marine phosphorus cycle," says the paper's lead author Ben Van Mooy, a biochemist at WHOI.
Much like phosphorus-based fertilizers boost the growth of plants on land, phosphorus in the ocean promotes the production of microbes and tiny marine plants called phytoplankton, which compose the base of the marine food chain.
Phosphonate mystery
It's been unclear exactly how phytoplankton are using the most abundant forms of phosphorus found in the ocean--phosphates and a strange form of phosphorus called phosphonates.
"Phosphonates have always been a huge mystery," Van Mooy says.
"No one's been able to figure out exactly what they are, and more importantly, if they're made and consumed quickly by microbes, or if they're just lying around in the ocean."
To find out more about phosphonates and how microbes metabolize them, the researchers took samples of seawater at a series of stations during a research cruise from Bermuda to Barbados.
They added phosphate to the samples so they could see the microbes in action.
The research team used ion chromatography onboard ship for water chemistry analyses, which allowed the scientists to observe how quickly microbes reacted to the added phosphate in the seawater.
"The ion chromatograph [IC] separates out the different families of molecules," explains Van Mooy.
"We added radioactive phosphate, then isolated the phosphonate to see if the samples became radioactive, too. It's the radioactive technique that let us see how fast phosphate was transformed to phosphonate."
Enter the microbes
The researchers found that about 5 percent of the phosphate in the shallow water samples was taken up by the microbes and changed to phosphonates.
In deeper water samples, which were taken at depths of 40 and 150 meters (131 feet and 492 feet), about 15 to 20 percent of the phosphates became phosphonates.
"Although evidence of the cycling of phosphonates has been mounting for nearly a decade, these results show for the first time that microbes are producing phosphonates in the ocean, and that it is happening very quickly," says paper co-author Sonya Dyhrman of Columbia University.
"An exciting aspect of this study was the application of the IC method at sea. In near-real-time, we could tell that the phosphate we added was being transformed to phosphonate."
Better understanding of phosphorus cycle
A better understanding of phosphorus cycling in the oceans is important, as it affects the marine food web and, therefore, the ability of the oceans to absorb atmospheric carbon dioxide.
The researchers say that solving the mystery of phosphonates also reinforces the need to identify the full suite of phosphorus biochemicals being produced and metabolized by marine microbes, and what physiological roles they serve for these cells.
"Such work will help us further resolve the complexities of how this critical element is cycled in the ocean," Dyhrman adds.
Grants from the Simons Foundation also supported the work.
-NSF-
Media Contacts
Cheryl Dybas, NSF
Showing posts with label FERTILIZER. Show all posts
Showing posts with label FERTILIZER. Show all posts
Thursday, May 28, 2015
Thursday, June 12, 2014
FERTILIZERS AND GREENHOUSE GAS
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| A Growing Summer Squash Plant |
FROM: NATIONAL SCIENCE FOUNDATION
How much fertilizer is too much for Earth's climate?
Helping farmers around the globe combat greenhouse gas emissions and climate change
Helping farmers around the globe apply more precise amounts of fertilizer nitrogen can combat climate change.
The study uses data from around the world to show that emissions of nitrous oxide (N2O), a greenhouse gas produced in soil following nitrogen addition, rise faster than previously expected when fertilizer rates exceed crop needs.
Nitrogen-based fertilizers spur greenhouse gas emissions by stimulating microbes in the soil to produce more nitrous oxide.
Nitrous oxide is the third most important greenhouse gas, behind carbon dioxide and methane.
Agriculture accounts for about 80 percent of human-caused nitrous oxide emissions worldwide, which have increased substantially in recent years due to increased nitrogen fertilizer use.
"Our motivation is to learn where to best target agricultural efforts to slow global warming," says MSU scientist Phil Robertson. Robertson is also director of the National Science Foundation (NSF) Kellogg Biological Station Long-term Ecological Research (LTER) site, one of 25 such NSF LTER sites around the globe, and senior author of the paper.
"Agriculture accounts for 8 to 14 percent of all greenhouse gas production globally. We're showing how farmers can help reduce this number by applying nitrogen fertilizer more precisely."
The production of nitrous oxide can be greatly reduced if the amount of fertilizer needed by crops is exactly the amount that's applied to farmers' fields.
When plants' nitrogen needs are matched with the nitrogen that's supplied, fertilizer has substantially less effect on greenhouse gas emissions, Robertson says.
"These results vastly improve the ability of research to inform climate change, food security and the economic health of the world's farmers," says Saran Twombly, a program director in NSF's Division of Environmental Biology, which funded the research through the LTER Program.
Lead author and MSU researcher Iurii Shcherbak notes that the research is especially applicable to fertilizer practices in under-fertilized areas such as sub-Saharan Africa.
"Because nitrous oxide emissions won't be accelerated by fertilizers until crops' nitrogen needs are met, more nitrogen fertilizer can be added to under-fertilized crops without much affecting emissions," says Shcherbak.
Adding less nitrogen to over-fertilized crops elsewhere, however, would deliver major reductions to greenhouse gas emissions in those regions.
The study provides support for expanding the use of carbon credits to pay farmers for better fertilizer management and offers a framework for using this credit system around the world.
Carbon credits for fertilizer management are now available to U.S. corn farmers, says Robertson.
The research was also funded by MSU, the U.S. Department of Energy's Great Lakes Bioenergy Research Center and the Electric Power Research Institute.
-- Cheryl Dybas, NSF
-- Layne Cameron, MSU
Investigators
Douglas Landis
Thomas Schmidt
Katherine Gross
Stephen Hamilton
G. Philip Robertson
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