{"id":77891,"date":"2026-04-29T13:28:10","date_gmt":"2026-04-29T20:28:10","guid":{"rendered":"https:\/\/in.nau.edu\/news\/?p=77891"},"modified":"2026-04-29T14:17:11","modified_gmt":"2026-04-29T21:17:11","slug":"river-foodwebs","status":"publish","type":"post","link":"https:\/\/in.nau.edu\/news\/river-foodwebs\/","title":{"rendered":"Study finds warmer streams may weaken river food webs"},"content":{"rendered":"

Rising stream temperatures may be weakening the foundation of river food webs by altering how carbon moves through\u00a0these watery\u00a0ecosystems.<\/span>\u00a0<\/span><\/p>\n

In a\u00a0<\/span>new study published in\u00a0the journal\u00a0Ecosphere<\/span><\/a>, researchers from Northern Arizona University found that\u00a0when\u00a0water temperatures increase, microbes and aquatic insects process\u00a0fallen leaves, twigs and bark\u00a0more rapidly,\u00a0but a smaller fraction of\u00a0that\u00a0leaf litter supports their\u00a0growth\u00a0and a bigger fraction is\u00a0released\u00a0into the water and air as\u00a0carbon dioxide.\u00a0<\/span>\u00a0<\/span><\/p>\n

The findings point to a shift in how\u00a0river ecosystems\u00a0retain\u00a0energy under warming conditions, with implications for\u00a0plants and animals in rivers\u00a0across the western United States.<\/span>\u00a0<\/span><\/p>\n

\u201cWarming doesn\u2019t just speed up biological processes in streams\u2014it changes how efficiently organisms turn carbon into biomass, with more of it being lost as CO\u2082,\u201d said\u00a0Michael Zampini,\u00a0a\u00a0postdoctoral researcher\u00a0at NAU\u00a0and\u00a0the\u00a0lead author of the study.<\/span>\u00a0<\/span><\/p>\n

\"A<\/a>
For their study, Zampini and other NAU\u00a0researchers built a controlled stream system at\u00a0The Arboretum at Flagstaff.<\/figcaption><\/figure>\n

A\u00a0\u2018living laboratory\u2019\u00a0to track carbon flow<\/span><\/b>\u00a0<\/span><\/h3>\n

To examine how warming affects river processes,\u00a0the NAU\u00a0researchers built a controlled stream system at\u00a0<\/span>The Arboretum at Flagstaff<\/span><\/a>,\u00a0constructing 48 flow-through mini stream chambers inside a greenhouse. Using pond water, they manipulated\u00a0the water\u00a0temperature while\u00a0maintaining\u00a0natural light and water chemistry, simulating a range of stream conditions over two years.<\/span>\u00a0<\/span><\/p>\n

\u201cThis system\u00a0let\u00a0us 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,\u201d said Zampini.<\/span>\u00a0<\/span><\/p>\n

Within this system, the team used tracers to follow carbon from leaf litter\u2014the primary energy source in many forested rivers\u2014into microbes and caddisflies. By labeling leaves with a rare form of carbon, they directly measured how much carbon was retained as biomass,\u00a0how much of it was released into the water and air\u00a0as CO\u2082\u00a0and how much was\u00a0transferred to\u00a0microbes and insects, allowing them to quantify how effectively organisms converted\u00a0food into growth.<\/span>\u00a0<\/span><\/p>\n

Faster processing, lower retention in warming streams<\/span><\/b>\u00a0<\/span><\/h3>\n

The researchers found that as\u00a0temperatures increased, decomposition rates rose, but a larger share of carbon was lost as CO\u2082 rather than incorporated into biomass. Caddisflies showed a distinct thermal response, with low temperatures limiting\u00a0their\u00a0activity, intermediate temperatures maximizing\u00a0their\u00a0efficiency, and higher temperatures increasing\u00a0their\u00a0consumption without corresponding gains in biomass. Together, these patterns\u00a0indicate\u00a0that warming\u00a0releases more carbon into the atmosphere and converts less carbon into\u00a0biomass.<\/span>\u00a0<\/span><\/p>\n

\"How<\/a>
This graphic shows how warming shifts carbon use in stream ecosystems, increasing carbon loss as CO\u2082 and reducing the amount converted into biomass by microbes and aquatic insects during leaf decomposition.<\/figcaption><\/figure>\n

\u201cEven when consumption increases, the system becomes less efficient\u2014more carbon goes to respiration and less to building the food web,\u201d said Jane Marks, professor in the Department of Biological Sciences and the Center for Ecosystem Science and Society\u00a0(Ecoss)\u00a0at NAU.<\/span>\u00a0<\/span><\/p>\n

In rivers across the Southwest, where aquatic insects link leaf litter to\u00a0animals higher on the food chain\u00a0such as fish, this shift has broader implications.\u00a0Declines in\u00a0carbon use efficiency\u00a0for microbes and aquatic insects mean\u00a0a greater proportion of carbon entering rivers may be lost to the atmosphere, reducing energy available to support aquatic food webs.\u00a0<\/span>\u00a0<\/span><\/p>\n

\u201cWhen 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,\u201d Marks\u00a0said.<\/span>\u00a0<\/span><\/p>\n

Other researchers involved in the study included University of Alabama professor Steven Thomas and Northern Arizona University researchers George Koch, Benjamin Koch, Paul\u00a0Dijkstra\u00a0and Victor\u00a0Leshyk\u00a0at\u00a0Ecoss. The research was funded by the National Science Foundation (DEB-1120343).<\/span>\u00a0<\/span><\/p>\n

\"Northern<\/span><\/p>\n


\nJill Kimball | NAU Communications
\n(928) 523-2282 | jill.kimball@nau.edu<\/a><\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Rising stream temperatures may be weakening the foundation of river food webs by altering how carbon moves through\u00a0these watery\u00a0ecosystems.\u00a0 In a\u00a0new study published in\u00a0the journal\u00a0Ecosphere, researchers from Northern Arizona University found that\u00a0when\u00a0water temperatures increase, microbes and aquatic insects process\u00a0fallen leaves, twigs and bark\u00a0more rapidly,\u00a0but a smaller fraction of\u00a0that\u00a0leaf litter supports their\u00a0growth\u00a0and a bigger fraction is\u00a0released\u00a0into…<\/a><\/p>\n","protected":false},"author":95,"featured_media":77897,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[11],"tags":[],"class_list":["post-77891","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research-academics"],"acf":[],"_links":{"self":[{"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/posts\/77891","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/users\/95"}],"replies":[{"embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/comments?post=77891"}],"version-history":[{"count":0,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/posts\/77891\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/media\/77897"}],"wp:attachment":[{"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/media?parent=77891"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/categories?post=77891"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/tags?post=77891"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}