Physical and Biogeochemical Processes Driving Methane Sources, Sinks and Emissions in Aquatic Systems: The Past, Present and Future under Global Change

The atmospheric concentration of methane, an emerging greenhouse gas with a high warming potential, is increasing at an alarming rate likely due to human-induced global change. While considerable budget uncertainties remain, it is evident that both natural and artificial waterbodies contribute substantially to global methane emissions. Many studies quantify methane emissions through in situ measurements, e.g. via flux chambers or eddy covariance techniques. Few studies, however, seek a more mechanistic understanding by examining methane dynamics in the water column and sediments to define the physical-biogeochemical processes and their feedbacks that drive methane production, transport, and ultimate fate. Importantly, methane has a relatively short residence time in the atmosphere (about a decade), making it a mitigable greenhouse gas and therefore of great relevance for carbon emission management. Unfortunately, mitigation and the ability to predict future emissions are only possible with a comprehensive understanding of methane dynamics in aquatic systems.

The atmospheric methane contribution from inland and coastal waters remains largely uncertain, mainly due to current mechanistic knowledge gaps. While lakes and reservoirs have been largely addressed in temperate locations, methane data are missing from remote areas. Finally, methane is unusual in aquatic systems given that its oxidation can be nearly as large as its production, highlighting the importance of focusing on both sources and sinks. Thus, predicting the effect of climate change and eutrophication on oxidation is as important as studying methane production hotspots.

The goals of this Research Topic are to encourage interdisciplinary studies that investigate:

• physical-biogeochemical drivers of aquatic methane production;
• methane oxidation;
• novel methane production pathways;
• methane mass transport; and
• paleolimnological methane studies

All are important to constrain present and future methane emissions from inland and ocean waters. These study outcomes will lead to better understanding and promotion of new insights into the biogeochemical processes that drive methane production and oxidation, and their response to key environmental variables (i.e. temperature, dissolved oxygen, nutrients). By improving our theoretical knowledge, we will be able to develop more realistic models taking the actual processes and dependencies from environmental drivers and ecosystems into account, especially in the context of current global change. These combined approaches will bring together different disciplines, scientists, and stakeholders and aim for feasible and more sustainable mitigation strategies.

We welcome all contributions related to the physical-biogeochemical processes driving methane cycling in all-natural and artificial waterbodies, with a particular focus on global change including climate warming, eutrophication, and urbanization. We seek interdisciplinary studies investigating the effect and feedbacks between methane cycling on the waterbody ecology, physical-biogeochemical cycles, ecology, microbiology, and modeling. In situ, laboratory, and modeling studies or a combination are encouraged, as are studies addressing novel methane production mechanisms (i.e. “methane paradox”). Study areas can include all inland and ocean waters, as well as studies addressing local, regional, and global upscaling. Modeling studies and investigations into future projections of methane production, oxidation, and the resulting emission, and its response to global change scenarios, as well as potential mitigation measures are highly encouraged. Article types available for submission include original research, review articles, and perspectives.