Babbling brooks adding to climate change?

May 26, 2014 by Kelly April Tyrrell
Methane bubbles rising to the surface of fresh water.

(Phys.org) —Studying stream bubbles isn't exactly a walk in the park. What, with the mud and ticks, the long days hiking and swimming through mucky streams, the sun exposure and scratching brush.

But in the end, it may prove to be insightful. The coming from freshwater sources, new research suggests, may be a key and currently unaccounted for source of methane, the second-largest contributor to human-driven global climate change.

In a May 16 paper published in the journal Global Change Biology, University of Wisconsin-Madison graduate student John Crawford and his colleagues, including his advisor Emily Stanley, a UW-Madison professor in the Department of Zoology and the Center for Limnology, show freshwater may be contributing more methane gas to the environment than has previously been measured.

The work has the potential to change how climate scientists and others determine the greenhouse gas budget. It also has implications for agricultural regions, where nitrogen and sulfur-based runoff may impact local methane production.

"There have been recent suggestions that freshwater streams, rivers and lakes are important sources of methane to the atmosphere," says Crawford, who also works for the U.S. Geological Survey in Boulder, Colo.

In freshwater environments, comes from the metabolic byproducts of bacteria living in the organic-compound-rich, oxygen-poor sediments. Where oxygen, nitrogen or sulfur are high, methane is low because of the chemistry involved in its formation.

Wetlands are known sources of methane but the streams and rivers that drain them may also contribute to the overall methane budget. Just how much is little understood.

Babbling brooks adding to climate change?
A bubble trap collecting freshwater bubbles from Allequash Creek. Credit: Center for Limnology/John Crawford

Unlike carbon dioxide, which is highly soluble in water, methane exists in two forms in these freshwater sources: as a dissolved gas and encapsulated in bubbles that rise from sediments "like bubbles coming up in a can of soda," says Crawford. Few studies have measured the methane trapped in those bubbles.

Crawford and the research team studied the methane in bubbles emitted from Allequash Creek, a tributary of Trout Lake in Vilas County, Wisconsin, where the creek bed is a mix of mucky, organic wetland components and sandy glacial sediment. They also looked at three other area creeks: Mann Creek, Stevenson Creek and North Creek.

To measure the methane in bubbles as they rose through the water, the team created traps to capture them and the air they contained. They ran the air through a sensor called a gas chromatograph to determine how much methane was contained within it. The team also looked at the rate of bubble release across sample sites.

They found there was as much methane in bubbles emitted from Allequash Creek and the surrounding area as has been measured in other wetland and lake environments. The researchers estimate at least 50 percent more methane can be emitted by bubbles in the region as is dissolved in the water.

"We are missing half the story, at least in this area, if we don't include bubbles," Crawford said. The team believes the creek is representative of other similar bodies of water in the Northern Highlands Lake District of Wisconsin.

The study ran from May through November of 2013 and the team trudged out to the sampling sites every other day through that period, measuring bubble composition every other week.

Babbling brooks adding to climate change?
A stretch of the Allequash Creek in the Northern Highlands Lake District of Wisconsin. Credit: Center for Limnology/John Crawford

They were surprised to find methane-containing bubbles coming from sandy sediments, which are generally less organic-rich than mucky beds. However, the concentration of the gas was lower from sandy sediments than from the mucky methane "hot spots."

Crawford says it's surprising to find methane at all in these highly-oxygenated creeks, though the methane is coming from mostly oxygen-poor sediments that form their beds.

While the new study cannot adequately assess the global contribution of bubble-contained from freshwater sources to the environment, it shows it's an area worth further investigation. Methane can lead to ozone production and levels of the gas in the atmosphere are 150 percent higher than they were before the Industrial Revolution.

For Crawford, his interest lies in helping explain things that people can't see, though that bubbles can be seen and felt makes the work more fun, he says. He is driven by the idea that really small ecosystems—like the freshwater lakes, streams and rivers Wisconsin is known for—can potentially play a major role in the overall greenhouse gas pool.

"You are never going to get the budget right if you don't get all the pieces," he says.

Explore further: Global warming may increase methane emissions from freshwater ecosystems

More information: Crawford, J. T., Stanley, E. H., Spawn, S. A., Finlay, J. C., Loken, L. C. and Striegl, R. G. (2014), "Ebullitive methane emissions from oxygenated wetland streams." Global Change Biology. DOI: 10.1111/gcb.12614

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User comments : 12

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verkle
2.3 / 5 (15) May 26, 2014
Please---drop off the ubiquitous "climate change" phrases in titles and articles. It has become a religion to many, and the source of finance if somehow research can be connected to it. But the phrase is truly meaningless as climate always has and always will change.
Maggnus
3.6 / 5 (14) May 26, 2014
Please---drop the holier than thou pronouncements and vague references to an even vaguer global conspiracy. It has become a source of embarrassment to many, and the financial sources of denialism has fueled the disconnect. The conspiracy is not real, and the change of climate resulting from the unprecedented and unmitigated dumping of waste CO2 into the atmosphere has to be considered.
jerryjbrown
2.6 / 5 (10) May 26, 2014
Discovery and research is wonderful, but this browbeating on climate change is getting mundane...
Benni
2.2 / 5 (13) May 26, 2014
.........first it's humans, then cow farts, then methane & CO2 under a lake in Africa, forest fires (trees), and now guess what? It's ALL lifeforms. What a truly poignant discovery, and after millions of years of this isn't it truly amazing the planet's lifeforms continue as they always have in spite of all the episodic interruptions of ice ages creating the most dramatic climate changes the planet has ever known.

And don't ask me what happened to the dinosaurs, we probably ate them because they just became so darn pesky.
cantdrive85
2.1 / 5 (11) May 26, 2014
There must be a way to tax this climate changing atrocity!
barakn
5 / 5 (9) May 26, 2014
The title of this article is inaccurate, as "babbling" implies fast moving, oxygenated water moving over a substrate of gravel or rocks.
chrisn566
2.1 / 5 (7) May 26, 2014
Oh my god,enough.
Caliban
4.6 / 5 (9) May 26, 2014
"For Crawford, his interest lies in helping explain things that people can't see, though that bubbles can be seen and felt makes the work more fun, he says. He is driven by the idea that really small ecosystems—like the freshwater lakes, streams and rivers Wisconsin is known for—can potentially play a major role in the overall greenhouse gas pool.

"You are never going to get the budget right if you don't get all the pieces," he says.


Are you morons unable to comprehend what you read?

Nevermind -it was a rhetorical question.

Just like the guy said --you don't know how much of the CO2 is added antropogenically, if you can't quantify the individual inputs into the total.

And if you don't understand the magnitude of this single type of contribution, then you are even more profound morons than even I suspected.

In the end, the only surprise is going to be the realization of just how little of a couple of atmospheric gases it is going to take to ruin us all.

Sinister1812
4.2 / 5 (10) May 26, 2014
The brooks aren't babbling nearly as much as the denialists here.
rwinners
3 / 5 (2) May 26, 2014
..... and don't fuck with our "babbling brooks"!
Maggnus
3.5 / 5 (11) May 27, 2014
There must be a way to tax this climate changing atrocity!
Why would you want to tax it?That seems like a highly suspect way of dealing with the issues, especially when there are already better, less intrusive ways to do it.

Why do you have to be such a contrarian all the time canthinkforhimself?
cantdrive85
1.9 / 5 (9) May 27, 2014
Why do you have to be such a contrarian all the time canthinkforhimself?

I'm pretty sure that sentence is contradictory.