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!
Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter
17.08.2017 | Swansea University
Climate change: In their old age, trees still accumulate large quantities of carbon
17.08.2017 | Universität Hamburg
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
21.08.2017 | Materials Sciences
21.08.2017 | Health and Medicine
21.08.2017 | Materials Sciences