Warming Streams Disrupt River Food Webs

Study finds rising temperatures reduce carbon retention, threatening aquatic ecosystems

Apr. 18, 2026 at 3:18am

Got story updates? Submit your updates here. ›

A bold, abstract painting in earthy tones featuring sweeping geometric shapes and botanical patterns, conceptually representing the complex flow of carbon through a river system and the disruption caused by warming.An abstract illustration depicting the disruption of carbon cycling in river ecosystems due to rising temperatures.Flagstaff Today

A new study from Northern Arizona University found that as stream temperatures rise, microbes and aquatic insects process leaf litter more rapidly, but a smaller fraction of that carbon is retained as biomass. Instead, more carbon is released into the water and air as CO₂, weakening the foundation of river food webs and reducing energy available to support aquatic life.

Why it matters

In rivers across the Southwest, aquatic insects play a crucial role in linking leaf litter to higher trophic levels like fish. This shift towards less efficient carbon use means a greater proportion of carbon entering rivers may be lost to the atmosphere, reducing the energy available to sustain aquatic food webs, with potential impacts on fisheries, water quality, and overall ecosystem stability.

The details

The NAU researchers built a controlled stream system at The Arboretum at Flagstaff, constructing 48 flow-through mini stream chambers inside a greenhouse. Using pond water, they manipulated the water temperature while maintaining natural light and water chemistry, simulating a range of stream conditions over two years. By labeling leaves with a rare form of carbon, they directly measured how much carbon was retained as biomass, how much was released into the water and air as CO₂, and how much was transferred to microbes and caddisflies.

  • The study was published in the journal Ecosphere in April 2026.
  • The research was conducted over a two-year period at the controlled stream system in Flagstaff.

The players

Michael Zampini

A postdoctoral researcher at Northern Arizona University and the lead author of the study.

Jane Marks

A professor in the Department of Biological Sciences and the Center for Ecosystem Science and Society (Ecoss) at Northern Arizona University.

The Arboretum at Flagstaff

The location where the NAU researchers built the controlled stream system to simulate a range of stream conditions.

Got photos? Submit your photos here. ›

What they’re saying

“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.”

— Michael Zampini, Postdoctoral researcher

“Even when consumption increases, the system becomes less efficient—more carbon goes to respiration and less to building the food web.”

— Jane Marks, Professor

What’s next

The researchers plan to continue studying how warming affects carbon cycling and energy flow in river ecosystems across the western United States.

The takeaway

This study highlights how climate change-driven warming can disrupt the fundamental processes that support river food webs, with potentially far-reaching consequences for aquatic life and the communities that depend on healthy river ecosystems.