Title | Dominance of Diffusive Methane Emissions From Lowland Headwater Streams Promotes Oxidation and Isotopic Enrichment |
Publication Type | Journal Article |
Year of Publication | 2022 |
Authors | Robison AL, Wollheim WM, Perryman CR, Cotter AR, Mackay JE, Varner RK, Clarizia P, Ernakovich JG |
Journal | Frontiers in Environmental Science |
Volume | 9 |
Pagination | 791305 |
ISSN | 2296-665X |
Abstract | 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. |
URL | https://www.frontiersin.org/articles/10.3389/fenvs.2021.791305/full |
DOI | 10.3389/fenvs.2021.791305 |
Citation Key | robison_dominance_2022 |