Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Amazon River Exhales Virtually All Carbon Taken Up by Rain Forest

22.05.2013
The Amazon rain forest, popularly known as the lungs of the planet, inhales carbon dioxide as it exudes oxygen. Plants use carbon dioxide from the air to grow parts that eventually fall to the ground to decompose or get washed away by the region's plentiful rainfall.

Until recently people believed much of the rain forest's carbon floated down the Amazon River and ended up deep in the ocean. University of Washington research showed a decade ago that rivers exhale huge amounts of carbon dioxide – though left open the question of how that was possible, since bark and stems were thought to be too tough for river bacteria to digest.

A study published this week in Nature Geoscience resolves the conundrum, proving that woody plant matter is almost completely digested by bacteria living in the Amazon River, and that this tough stuff plays a major part in fueling the river's breath.

The finding has implications for global carbon models, and for the ecology of the Amazon and the world's other rivers.

"People thought this was one of the components that just got dumped into the ocean," said first author Nick Ward, a UW doctoral student in oceanography. "We've found that terrestrial carbon is respired and basically turned into carbon dioxide as it travels down the river."

Tough lignin, which helps form the main part of woody tissue, is the second most common component of terrestrial plants. Scientists believed that much of it got buried on the seafloor to stay there for centuries or millennia. The new paper shows river bacteria break it down within two weeks, and that just 5 percent of the Amazon rainforest's carbon ever reaches the ocean.

"Rivers were once thought of as passive pipes," said co-author Jeffrey Richey, a UW professor of oceanography. "This shows they're more like metabolic hotspots."

When previous research showed how much carbon dioxide was outgassing from rivers, scientists knew it didn't add up. They speculated there might be some unknown, short-lived carbon source that freshwater bacteria could turn into carbon dioxide.

"The fact that lignin is proving to be this metabolically active is a big surprise," Richey said. "It's a mechanism for the rivers' role in the global carbon cycle – it's the food for the river breath."

The Amazon alone discharges about one-fifth of the world's freshwater and plays a large role in global processes, but it also serves as a test bed for natural river ecosystems.

Richey and his collaborators have studied the Amazon River for more than three decades. Earlier research took place more than 500 miles upstream. This time the U.S. and Brazilian team sought to understand the connection between the river and ocean, which meant working at the mouth of the world's largest river – a treacherous study site.

"There's a reason that no one's really studied in this area," Ward said. "Pulling it off has been quite a challenge. It's a humongous, sloppy piece of water."

The team used flat-bottomed boats to traverse the three river mouths, each so wide that you cannot see land, in water so rich with sediment that it looks like chocolate milk. Tides raise the ocean by 30 feet, reversing the flow of freshwater at the river mouth, and winds blow at up to 35 mph.

Under these conditions, Ward collected river water samples in all four seasons. He compared the original samples with ones left to sit for up to a week at river temperatures. Back at the UW, he used newly developed techniques to scan the samples for some 100 compounds, covering 95 percent of all plant-based lignin. Previous techniques could identify only 1 percent of the plant-based carbon in the water.

Based on the results, the authors estimate that about 45 percent of the Amazon's lignin breaks down in soils, 55 percent breaks down in the river system, and 5 percent reaches the ocean, where it may break down or sink to the ocean floor.

"People had just assumed, 'Well, it's not energetically feasible for an organism to break lignin apart, so why would they?'" Ward said. "We're thinking that as rain falls over the land it's taking with it these lignin compounds, but it's also taking with it the bacterial community that's really good at eating the lignin."

The research was supported by the Gordon and Betty Moore Foundation, the National Science Foundation and the Research Council for the State of São Paulo. Co-authors are Richard Keil at the UW; Patricia Medeiros and Patricia Yager at the University of Georgia; Daimio Brito and Alan Cunha at the Federal University of Amap in Brazil; Thorsten Dittmar at Carl von Ossietzky University in Germany; and Alex Krusche at University of São Paulo in Brazil.

For more information, contact Ward at nickward@uw.edu or 858-531-1558 and Richey at jrichey@uw.edu or 206-368-1906.

Hannah Hickey | Newswise
Further information:
http://www.uw.edu

More articles from Earth Sciences:

nachricht By saving cost and energy, the lighting revolution may increase light pollution
23.11.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

nachricht Frictional Heat Powers Hydrothermal Activity on Enceladus
23.11.2017 | Universität Heidelberg

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Underwater acoustic localization of marine mammals and vehicles

23.11.2017 | Information Technology

Enhancing the quantum sensing capabilities of diamond

23.11.2017 | Physics and Astronomy

Meadows beat out shrubs when it comes to storing carbon

23.11.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>