Not Playing by the Rules: USU Researcher Explores Filamentous Algae Dynamics in Rivers

by Mary-Ann Muffoletto, Utah State University
December 19, 2025

Algae is a ubiquitous feature in waterways throughout the globe, including western North America. Slippery, green epilithic algae is a familiar sight on river rocks. Toxic blue-green algae – cyanobacteria – is a visually interesting, yet worrisome phenomenon. Increasingly prevalent filamentous algae, with its long, voluminous green strands joins the picture, and is presenting new questions for scientists, recreationalists and land managers.

“In recent years, people have noted very large filamentous algae blooms in big, western rivers in the United States, including in Utah’s Provo, Jordan and Bear Rivers,” says Utah State University river ecologist and statistician Alice Carter. “They create a ton of biomass and grow filaments several meters long. Though not toxic, they’re a nuisance interfering with traditional recreational river uses, including kayaking and fishing. Further, these huge blooms are essentially a food web dead end that don’t support fisheries or macroinvertebrate communities.”

Carter and colleagues from the University of Montana and Woods Hole Oceanographic Institution in Massachusetts have been studying these massive plant-like organisms in the Upper Clark Fork River in western Montana. They report findings in the Dec. 9, 2025 online issue of the journal Ecology. The research was supported by the National Science Foundation.

Keep reading: https://www.usu.edu/today/story/not-playing-by-the-rules-usu-researcher-explores-filamentous-algae-dynamics-in-rivers

Read the Ecology paper: https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.70262