MBL, WOODS HOLE, MA—Increasing nitrogen runoff from urban and agriculture land-use is interfering with our streams’ and rivers’ natural processes for reducing this pollutant before it endangers delicate downstream ecosystems, reports a nationwide team of 31 ecologists, including two from the MBL (Marine Biological Laboratory) Ecosystems Center.
The findings, published in the March 13 issue of Nature, are based on a major study of 72 streams in 8 regions across the U.S. and Puerto Rico. “It was a collaborative effort by many leading aquatic ecologists working to solve a complex problem regarding the role of streams in reducing pollution,” says lead author Patrick Mulholland of the Oak Ridge National Laboratory and University of Tennessee.
Just how important are streams" “They are effective filters that can help prevent nitrate pollution from reaching lakes and coastal oceans, where it can cause noxious algal blooms and lead to oxygen depletion and death of fish and shellfish, as has been recently reported in the Gulf of Mexico,” says Mulholland.
Building on an earlier study (Science, April 6, 2001) that demonstrated that even the smallest streams can filter up to half of the inorganic nitrogen that enters them, the scientists launched the new study to learn how increased nitrogen pollution is affecting this process. They analyzed data collected from a variety of waterways, including streams in urban and agricultural settings, where land-use dominates the landscape and degrades water quality.
“Our findings demonstrate that streams containing excess nitrogen are less able to provide the natural nitrogen removal service known as denitrification,” says Bruce Peterson, a senior scientist at the MBL Ecosystems Center and one of the study’s authors. In denitrification, bacteria help convert nitrate in the water to nitrogen gases that then escape to the atmosphere.
“The new research demonstrates that although denitrification rates increase as nitrate concentrations increase, the efficiency of denitrification and nitrate assimilation decline as nitrogen loading increases,” adds Peterson. “This means humans can easily overload stream and rivers networks to the point that nitrate removal is not sufficient to prevent eutrophication downstream, the scenario where algae grow out of the control and oxygen may fall to unhealthy levels.”
To gauge the effects of high levels of nitrogen runoff on waterways, the scientists used the stable isotope 15N (nitrogen 15) to track nitrogen movement through each study stream. They also developed ecological models to study nitrate removal from water within river networks, which develop as small streams flow into larger streams and rivers. The models showed that the entire stream network is important in removing nitrogen from stream water.
The ecologists say these and other findings in the Nature study underscore the importance of controlling human-generated nitrogen runoff, and provide critical information to land-use managers contemplating large-scale land conversions for projects including corn farming for biofuels production.
Gina Hebert | EurekAlert!
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences