Widespread methane formation byCyanobacteriain aquatic and terrestrial ecosystems

Abstract

<jats:title>Abstract</jats:title><jats:p>Evidence is accumulating to challenge the paradigm that biogenic methanogenesis, traditionally considered a strictly anerobic process, is exclusive to <jats:italic>Archaea</jats:italic>. Here we demonstrate that Cyanobacteria living in marine, freshwater and terrestrial environments produce methane at substantial rates under light and dark oxic and anoxic conditions, forming a link between light driven primary productivity and methane production in globally relevant group of phototrophs. Biogenic methane production was enhanced during oxygenic photosynthesis and directly attributed to the cyanobacteria by applying stable isotope labelling techniques. We suggest that formation of methane by <jats:italic>Cyanobacteria</jats:italic> may contribute to methane accumulation in oxygen-saturated surface waters of marine and freshwater ecosystems. Moreover, in these environments, cyanobacterial blooms already do, and might further occur more frequently during future global warming and thus have a direct feedback on climate change. We further highlight that cyanobacterial methane production not only affects recent and future global methane budgets, but also has implications for inferences on Earth’s methane budget for the last 3.5 billion years, when this phylum is thought to have first evolved.</jats:p>

Phosphonates: Their Natural Occurrence and Physiological Role

“…Up to 4% of the methane on Earth comes from the oxygen-rich waters through the cleavage of the highly unreactive carbon-to-phosphorus bond in methyl phosphonate [32]. The production of methylphosphonic acid (MPn) by cyanobacteria or marine archaea related to N. maritimus and its subsequent decomposition by phosphate-starved bacterioplankton may partially explain the production of methane in oceanic and lake surfaces [33][34][35]. The concentration of methane in the upper ocean being above equilibrium with the atmosphere is known as the oceanic methane paradox [36,38].…”

Methane production by three widespread marine phytoplankton species: release rates, precursor compounds, and potential relevance for the environment

“…Significant quantities of CH 4 , produced in upper oxic waters near the air-water interface, might overcome oxidation and thus significantly contribute to CH 4 fluxes from aquatic environments to the atmosphere (Bogard et al, 2014). It turned out that in situ CH 4 production in the upper oxic waters is a common feature of both oceans and lakes (Forster et al, 2009;Reeburgh, 2007;Tang et al, 2014;Donis et al, 2017;Bižić-Ionescu et al, 2018b;Bange et al, 1994). These results have stimulated the scientific community to study in more detail the phenomenon of CH 4 occurrence in oxygenated surface waters.…”

An Exploration of Common Greenhouse Gas Emissions by the Cyanobiont of the Azolla–Nostoc Symbiosis and Clues as to Nod Factors in Cyanobacteria

“…Cyanobacteria have been shown to produce methane from aquatic and terrestrial ecosystems [26]. It is a stark reality that biogenic methane production by cyanobacteria affects the recent and future methane budgets, and is also part of a protracted time frame (3.5 billion years) since their evolutionary beginnings, where they would have furnished methane to the ambient environment [26].…”

“…Cyanobacteria have been shown to produce methane from aquatic and terrestrial ecosystems [26]. It is a stark reality that biogenic methane production by cyanobacteria affects the recent and future methane budgets, and is also part of a protracted time frame (3.5 billion years) since their evolutionary beginnings, where they would have furnished methane to the ambient environment [26]. It is hypothesized that the increased rates of hydrogen production in diazotrophs, such as the cyanobiont N. azollae, promote the production of methane through the transfer of hydrogen gas into hydrogenotrophic methanogenic bacteria in the ambient environment [26].…”