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Inland waters are the largest natural source of methane (CH 4 ) to the atmosphere, yet the contribution from small streams to this flux is not clearly defined. To fully understand CH 4 emissions from streams and rivers, we must consider the relative importance of CH 4 emission pathways, the prominence of microbially-mediated production and oxidation of CH 4 , and the isotopic signature of emitted CH 4 . Here, we construct a complete CH 4 emission budgets for four lowland headwater streams by quantifying diffusive CH 4 emissions and comparing them to previously published rates of ebullitive emissions. We also examine the isotopic composition of CH 4 along with the sediment microbial community to investigate production and oxidation across the streams. We find that all four streams are supersaturated with respect to CH 4 with diffusive emissions accounting for approximately 78–100% of total CH 4 emissions. Isotopic and microbial data suggest CH 4 oxidation is prevalent across the streams, depleting approximately half of the dissolved CH 4 pool before emission. We propose a conceptual model of CH 4 production, oxidation, and emission from small streams, where the dominance of diffusive emissions is greater compared to other aquatic ecosystems, and the impact of CH 4 oxidation is observable in the emitted isotopic values. As a result, we suggest the CH 4 emitted from small streams is isotopically heavy compared to lentic ecosystems. Our results further demonstrate streams are important components of the global CH 4 cycle yet may be characterized by a unique pattern of cycling and emission that differentiate them from other aquatic ecosystems.
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Waterfalls enhance regional methane emissions by enabling dissolved methane to bypass microbial oxidation
River waters are significant sources of atmospheric methane whose local emissions increase with river slope and turbulence. However, when integrated regionally, the amount of dissolved methane released to the atmosphere is uninfluenced by local changes in turbulence when no additional loss mechanisms are present. Here we tested the hypothesis that waterfalls enhance both local and regional atmospheric methane emissions if microbial methane oxidation is significant in river waters. Rates of net atmospheric emission and net aerobic methane oxidation were measured in river waters containing waterfalls across western New York revealing that methane oxidation can diminish atmospheric emissions when turbulence is less. However, at waterfalls, 88 ± 1% of the dissolved methane supersaturation was released to the atmosphere, increasing net methane emission rates substantially beyond oxidation (0.1–16.2 × 10^6 nM d^-1 for waterfall emission; 10–39 nM d^-1 for oxidation), and ultimately enhancing regional methane emissions by enabling dissolved methane to bypass an oxidative sink.
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- PAR ID:
- 10576322
- Publisher / Repository:
- Springer Nature
- Date Published:
- Journal Name:
- Communications Earth & Environment
- Volume:
- 6
- Issue:
- 1
- ISSN:
- 2662-4435
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1038/s43247-025-02060-3
