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PFAS exposure suppresses leaf litter decomposition in a stream ecosystem
Alison M Zachritz1, Abagael N Pruitt1, Therese M Reisch1
1Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.
Aquatic Toxicology (Amsterdam, Netherlands)
|August 11, 2026
Summary
Per- and polyfluoroalkyl substances (PFAS) slow down organic matter decomposition and microbial respiration in streams. This research shows PFAS contamination impacts stream ecosystems beyond direct toxicity.
Area of Science:
- Environmental chemistry
- Ecosystem ecology
- Biogeochemical cycles
Background:
- Decomposition of organic matter is vital for carbon and nutrient cycling in ecosystems.
- Anthropogenic impacts, such as contaminants, can alter decomposition processes in streams.
- Per- and polyfluoroalkyl substances (PFAS) are persistent, widespread in freshwater, but their effects on stream organic matter processing are poorly understood.
Purpose of the Study:
- To investigate the influence of PFAS on leaf litter decomposition and microbial activity in streams.
- To determine if PFAS contamination affects ecosystem-level processes in freshwater environments.
Main Methods:
- A field study compared a PFAS-impacted stream section to an upstream site.
- A laboratory experiment involved dosing aquatic mesocosms with perfluorooctane sulfonate (PFOS) and leaf packs.
- Multiple lines of evidence, including decomposition rates, microbial respiration, and dissolved organic carbon (DOC), were analyzed.
Main Results:
- Leaf litter decomposition and microbial respiration were significantly reduced downstream of a PFAS point source in the field study.
- In laboratory mesocosms, PFOS exposure did not alter decomposition rates but led to decreased respiration and increased DOC on day 28.
- These findings suggest PFAS can suppress microbial activity and inhibit carbon processing.
Conclusions:
- PFAS contamination can negatively affect ecosystem functions in streams, specifically organic matter processing.
- Concerns about PFAS extend to ecosystem-level impacts, not just direct toxicity to organisms.
- Further research is necessary to elucidate the mechanisms and broader implications of PFAS on aquatic ecosystems.
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