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


































