Rivers are carbon processors, not inert pipelines

European Science Foundation: Microorganisms in rivers and streams play a crucial role in the global carbon cycle that has not previously been considered. Freshwater ecologist Dr Tom Battin, of the University of Vienna, told a COST ESF Frontiers of Science conference in October that our understanding of how rivers and streams deal with organic carbon has changed radically.

Microorganisms such as bacteria and single celled algae in rivers and streams decompose organic matter as it flows downstream. They convert the carbon it contains into carbon dioxide, which is then released to the atmosphere.

Recent estimates by Battin’s team and others conclude there is a net flux, or outgassing, of carbon dioxide from the world’s rivers and streams to the atmosphere of at least two-thirds to three-quarters of a gigatonne (Gt) of carbon per year. This flux has not been taken into account in the models of the global carbon cycle used to predict climate change.

“Surface water drainage networks perfuse and integrate the landscape, across the whole planet,” says Battin, “but they are missing from all global carbon cycling, even from the IPCC (Intergovernmental Panel on Climate Change) reports. Rivers are just considered as inert pipelines, receiving organic carbon from Earth and transporting it to the ocean.” This thinking, according to Battin, has changed radically in the last few years.

…In a disturbing development, Battin’s team lab has recently found that engineered nanoparticles can significantly compromise the freshwater microbes involved in carbon cycling. “This finding is a real challenge to science,” says Battin. “Engineered nanoparticles such as titanium dioxide are expected to increase in the environment, but it remains completely unknown how they might affect the functioning of ecosystems.”

The Rhine flows through Schaffhausen, shot by Pedro María Reyes Vizcaíno, Wikimedia Commons, under the Creative Commons Attribution ShareAlike 2.5 License