Warmer Streams Release More Atmospheric Carbon, Making Less Available for Food Webs, New Study Shows

  

    A new paper published in the journal Ecosphere by researchers at Northern Arizona University (NAU) shows that warming streams may release more CO2 into the atmosphere and make less available to support food webs. The research found that microbes and aquatic insects process and decompose organic matter faster in warmer water. They also found that a smaller fraction of that organic matter, such as leaf litter, supports their growth, and a bigger fraction is released as CO2.

     According to Phys.org

"Warming doesn't just speed up biological processes in streams—it changes how efficiently organisms turn carbon into biomass, with more of it being lost as CO₂," said Michael Zampini, a postdoctoral researcher at NAU and the lead author of the study.

     The researchers built a controlled stream system at The Arboretum at Flagstaff and studied it for two years.

"This system let us manipulate temperature while keeping everything else as close to a real stream as possible, which is critical for understanding how these processes actually play out in nature," said Zampini.

     The research allowed them to determine how effectively and efficiently organisms converted food into growth. They found that warmer water resulted in faster decomposition but less retention of carbon.

“Caddisflies showed a distinct thermal response, with low temperatures limiting their activity, intermediate temperatures maximizing their efficiency, and higher temperatures increasing their consumption without corresponding gains in biomass.”

"Even when consumption increases, the system becomes less efficient—more carbon goes to respiration and less to building the food web," said Jane Marks, professor in the Department of Biological Sciences and the Center for Ecosystem Science and Society (Ecoss) at NAU.

"When less carbon is retained in biomass, there is less energy available to support aquatic life, which can ripple through the food web and ultimately affect fisheries, water quality, and ecosystem stability that people depend on," Marks said.

     The paper defines carbon use efficiency (CUE) as “the proportion of consumed carbon (C) retained as biomass.”

     This research is logical, straightforward, and would be generally expected, as more heat often speeds up chemical reactions. However, it importantly shows the details of heat in streams and especially how it influences the carbon metabolism of caddisflies. The study utilized carbon isotopes as tracers to measure carbon metabolism.

 

 

References:

 

Warmer streams may be draining river food webs by sending more carbon into the air. Science X staff. Phys.org. April 17, 2026. Warmer streams may be draining river food webs by sending more carbon into the air

Temperature accelerates decomposition and controls carbon use efficiency for microbes and shredding caddisflies. Michael C. Zampini, Steven A. Thomas, Benjamin J. Koch, George Koch, Paul Dijkstra, Jane C. Marks. Ecosphere. Volume 17, Issue 4. April 1, 2026. Temperature accelerates decomposition and controls carbon use efficiency for microbes and shredding caddisflies - Zampini - 2026 - Ecosphere - Wiley Online Library