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!
Joint research project on wastewater for reuse examines pond system in Namibia
19.12.2016 | Technische Universität Darmstadt
Scientists produce a new roadmap for guiding development & conservation in the Amazon
09.12.2016 | Wildlife Conservation Society
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
18.01.2017 | Life Sciences
18.01.2017 | Health and Medicine
17.01.2017 | Earth Sciences