All freshwater streams and rivers actually release carbon dioxide, but the source of those emissions has for years been unclear to scientists.
Now, researchers have shown that the greenhouse gas appears in streams by way of two different sources -- either as a direct pipeline for groundwater and carbon-rich soils, or from aquatic organisms releasing the gas through respiration and natural decay.
CO2's origins -- land or life -- depend largely on the size of the stream or river, according to a paper published Aug. 10 in Nature Geosciences. These findings shed light on the role freshwater rivers play in the global carbon cycle.
"This paper validates that in certain systems, a lot of the carbon dioxide is coming from terrestrial systems, but as you get to larger rivers, that connection to the land becomes less and less strong. This is the first broad study to show that," said co-author David Butman, a University of Washington assistant professor of environmental and forest sciences and of civil and environmental engineering.
The researchers found that smaller streams usually carry carbon dioxide that is produced by plants on land and then transferred to the water by way of soil and groundwater. That happens because at its headwaters, a small stream often is surrounded by trees and other plants that pull carbon out of the atmosphere and store or "sink" it in soils and biomass.
But in larger streams, most CO2 emissions are produced directly in the water itself. More plants and animals are present in larger rivers, and they use available oxygen and convert organic carbon to carbon dioxide through respiration.
Understanding how carbon dioxide ends up in streams and rivers will improve predictions of how changes to river systems affect the efficiency of terrestrial ecosystems at removing greenhouse gases from the atmosphere, researchers say.
"It is very important to know the sources of carbon dioxide in running waters as well as the processes controlling respiration and emissions if we are to understand what happens when the environment changes," said lead author Erin Hotchkiss, who completed the research while at Umeå University in Sweden.
Butman and Hotchkiss, along with other collaborators at Umeå University and the University of Wyoming, began working together about two years ago to see if they could pinpoint where the carbon dioxide measured in rivers and streams was coming from.
The researchers looked at long-term U.S. Geological Survey data from about 1,400 freshwater streams and rivers across the U.S., as well as data collected from more than 180 river monitoring sites. Their models showed that aquatic plants and animals produced about 30 percent of the carbon dioxide found in streams and rivers in the U.S. on average, and that number ranged from only 14 percent in the smallest streams to near 40 percent in large rivers.
The main takeaway, Butman said, is that rivers and streams don't all behave the same way with regard to putting out carbon dioxide. This study is one of the first attempts to identify the source of carbon in freshwater river systems at a very large scale, helping to further our understanding of the role streams and rivers play in the global carbon cycle.
"Figuring out how these streams fit into the larger carbon cycle is most important," he said.
The next step is to take the research beyond modeling and do actual broad-scale measurements of CO2 along entire networks of streams, Butman added.
Other co-authors are Robert O. Hall Jr. at the University of Wyoming; and Ryan Sponseller, Jonatan Klaminder, Hjalmar Laudon, Martin Rosvall and Jan Karlsson at Umeå University.
This research was funded by Kempestifelserna, a foundation in Sweden, with additional data and analysis support through Butman and the U.S. Geological Survey's LandCarbon Program.
For more information, contact Butman at email@example.com or 206-685-0953.
Michelle Ma | EurekAlert!
Monitoring lava lake levels in Congo volcano
16.05.2018 | Seismological Society of America
Ice stream draining Greenland Ice Sheet sensitive to changes over past 45,000 years
14.05.2018 | Oregon State University
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.
The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...
Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.
Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...
A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.
Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
18.05.2018 | Power and Electrical Engineering
18.05.2018 | Information Technology
18.05.2018 | Information Technology