Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.28.225276v1?rss=1 Authors: Perez-Coronel, E., Beman, J. M. Abstract: Aquatic ecosystems are globally significant sources of the greenhouse gas methane to the atmosphere. However, methane is produced paradoxically in oxygenated water via at least three mechanisms, fundamentally limiting our understanding of overall methane production. Here we resolve these methane production mechanisms through methane measurements, {delta}13CH4 analyses, 16S rRNA sequencing, and metagenomics/transcriptomics applied to freshwater incubation experiments with multiple time points and treatments (addition of a methanogenesis inhibitor, dark, high-light). We captured significant paradoxical methane production, but show that methanogenesis was an unlikely methane source. In contrast, abundant freshwater bacteria metabolized methylphosphonate, similar to observations in marine ecosystems. Metatranscriptomics and stable isotopic analyses applied to experimental treatments also identified a potential methane production mechanism linked to (bacterio)chlorophyll metabolism by Cyanobacteria and especially Proteobacteria. Variability in these mechanisms across experiments indicates that multiple, widely-distributed bacterial groups and pathways can produce substantial quantities of methane in aquatic ecosystems. Copy rights belong to original authors. Visit the link for more info