They discovered that rivers breathe like humans

At first glance, the idea that rivers breathe seems like a poetic metaphor, but rivers do so just like us humans.

A team of scientists at the Pacific Northwest National Laboratory (PNNL) is taking a deeper look at river respiration.

Rivers, like living organisms, are in constant movement, absorbing oxygen from the air and releasing carbon dioxide and other gases into the atmosphere; a fundamental exchange for the countless forms of life that inhabit freshwater ecosystems.

Scientists have now discovered that rivers breathe, just like us, we inhale oxygen and exhale carbon dioxide (we inhale, the air passes from the nose to the throat and finally to the lungs, and we exhale a mixture of oxygen and carbon dioxide through the nose and mouth). Rivers do something similar through small organisms and organic matter. A new publication has detailed this breathing over many types of streams and rivers, and explores why some breathe more than others.

Do rivers breathe like we do?

All rivers breathe, large and small, absorbing oxygen and releasing carbon dioxide and other greenhouse gases such as methane.

The process is based on a series of complex chemical reactions carried out by tiny organisms such as bacteria and algae. These organisms absorb dissolved oxygen from water, just as we breathe air, and this cycle is essential for maintaining healthy oxygen levels in rivers and supporting a variety of aquatic organisms.

Likewise, small pieces of dead animals and plants living in rivers (mainly organic matter) also serve as food for water organisms and help keep the water clean. Microorganisms in the river break down this organic matter in a process called decomposition, releasing carbon dioxide and methane (two powerful greenhouse gases) into the atmosphere.

The breathing of a river does not always occur in the same place. In very wide rivers with a high flow of water, most of the respiration occurs in the water. However, in smaller streams, this should be looked for in the river bottom sediments, as these sediments are in direct contact with the organic matter, forming a very rich food source for all these microorganisms and bacteria.

Experts say the breathing process also produces emissions in the form of carbon dioxide, which is exhaled by organisms such as algae and bacteria found in streams and river ecosystems. And not only that, scientists have discovered that the size of sediment particles also affects the respiration of rivers. If there are larger rocks in the sediment, respiration will be more efficient than with smaller rocks. This means that some sediments "respire" much faster than others and, as a result, release more carbon dioxide. Therefore, the location and amount of respiration in a river system changes constantly and depends on both the physical properties of the river, as well as the volume of water and the size of sediment particles.

"Our team used models and data"explains Timothy Scheibe, scientist and geologist at the PNNL laboratory and one of the authors of the study published in the journal Frontiers in Water "to generate new information and develop forecasts to inform the decisions of natural resource management regulators".

the rivers breathe

Factors that modify river respiration

Several factors affect oxygen levels in rivers, including temperature, flow, and the presence of photosynthetic organisms.

The study details how some disturbances that occur outside of streams, such as wildfires, also affect their respiration by changing the way material flows into them. For example, dam construction and other changes in river flows alter natural oxidation processes and can lead to anaerobic (oxygen deficiency) conditions downstream.

Pollution can also cause eutrophication, a process that reduces oxygen levels and harms aquatic life.

All this data is interesting because it can help improve water quality management. By knowing that rivers breathe, scientists and policymakers can develop better strategies to clean rivers, and by knowing exactly how these bodies of water function, we can also better protect and care for them.

Water is life. "Understanding the principles behind processes and how they operate across systems is a key objective of our work."said PNNL field scientist Allison Myers-Pigg. “This knowledge provides the basis for building models that can predict the future state of rivers and streams, including the impact of major disturbances on them. Without this knowledge, we cannot make accurate predictions.".


  • Firnaaz Ahamed et al, Exploring the determinants of organic matter bioavailability through substrate-explicit thermodynamic modeling, Frontiers in Water (2023). DOI: 10.3389/frwa.2023.1169701

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