Streams May Add to Climate Change: Babbling Brook Bubbles Contain Methane

Could streams be adding to climate change? It turns out that the bubbles coming from freshwater sources could be a significant and unaccounted source of methane, which may impact climate models and reveal that our world may be warming more quickly than expected.

In freshwater environments, methane gas can come from bacteria living in the organic-compound-rich, oxygen-poor sediments beneath the water. Wetlands, for example, are a known source of methane. Now, scientists have found that other freshwater sources, such as streams and rivers, could also contribute to the total amount of methane.

"There have been recent suggestions that freshwater streams, rivers and lakes are important sources of methane to the atmosphere," said John Crawford, one of the researchers, in a news release.

Methane exists in two forms in freshwater sources; it can exist as a dissolved gas or can exist encapsulated in bubbles. That's why the scientists decided to take a closer look at four different creeks in order to get a better sense at how much methane that these bubbles contained. They created traps that captured the bubbles emitted from the creeks and then ran the captured air through a sensor to determine how much methane was contained within it.

So what did they find? It turns out that there was much more methane in the bubbles from one creek in particular, called Allequash Creek, and the surrounding area than has been measured in other wetland and lake environments. In fact, the scientists estimated that at least 50 percent more methane can be emitted from bubbles in the region.

"We are missing half of the story, at least in this area, if we don't include bubbles," said Crawford in a news release.

The findings reveal that bubbles in streams could potentially be a significant source of methane, and could affect climate models. While the study itself can't assess the global contribution of bubble-containing methane, it does reveal that this is an important area for future research.

The findings are published in the journal Global Change Biology.