This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Lakes may look like picturesque stopping points along a river or stream, but they can have a big influence on what happens to carbon as it moves through a landscape. New research suggests that the more lake-rich a network of streams is, the more carbon is released into the atmosphere rather than carried downstream.
The finding, published in Geophysical Research Letters, comes from researchers who studied 32 connected stream-and-lake networks in northern Sweden, measuring how much carbon was released into the atmosphere and how much continued downstream. They found that networks with 10 times more lake surface area had almost twice the carbon emissions. The results highlight a part of the carbon cycle that may have been overlooked by scientists.
Rather than treating lakes and streams as separate pieces of the landscape, Fredrik Alriksson, of Sweden's Umeå University, and colleagues argue that they need to be considered together as connected networks. Streams and rivers constantly pick up carbon from the land around them and carry it downstream toward larger rivers and eventually the ocean. However, some is transformed into gases, including carbon dioxide, and escapes from the water into the atmosphere.
How much carbon each route takes depends partly on how long the water stays within the aquatic network. A fast-flowing stream can carry carbon downstream relatively quickly, while a lake can slow the journey considerably, giving chemical and biological processes more time to act on the carbon. The researchers call the length of time water remains within a stream-and-lake network its "network residence time." In the Swedish networks they studied, this varied enormously, from just 42 minutes to as long as 29 years.
Lakes accounted for almost all of this residence time. To investigate what this means for the carbon cycle, the team repeatedly sampled the networks during four different periods: spring snowmelt, early summer, late-summer low flow and autumn high flow. They measured carbon dioxide emissions across more than 360 sections of streams and from 42 lakes, while also estimating how much dissolved carbon was being transported downstream.
The pattern was striking. Networks with 10 times more aquatic surface area had approximately 35 times longer residence times and 1.8 times higher carbon emissions relative to downstream carbon export. One likely explanation is that keeping carbon in the water longer gives microbes more opportunity to break down dissolved organic carbon.
Extract — continue reading at the source.
