Impact of methanotrophs, methanogens and geochemical conditions on net methane flux to the atmosphere from Arctic soils

On a global scale, soils contain more carbon than all vegetation and atmospheric sinks combined. However, this stored carbon is not permanently retained and can be readily released back to the atmosphere by biological and non-biological mechanisms (a process known as flux). In soil systems, microbial communities are the primary recyclers of carbon, including the conversion of soil carbon to gases, such as methane (CH4). This conversion is critical because CH4 is the second most significant greenhouse gas and has been rising in the atmosphere over the past forty years. Unfortunately, rates of CH4 release from Arctic soils appear to be increasing, which is significant because Arctic processes are responsible for > 25% of atmospheric CH4. As such, an urgent need exists to understand and quantify factors and mechanisms that influence Arctic CH4 flux, which will allow us to better predict climate conditions in the future.

As background, we quantified CH4 flux at 13 differing high Arctic sites near Ny-Alesund, Svalbard in 2010 in conjunction with the measurement of 58 geochemical and biological parameters in near-surface soils (work focused on the anaerobic-aerobic interface). However, statistical analyses showed only weak correlations among key near-surface microbial groups (i.e., methane-consuming methanotrophs and methane-producing methanogens), geochemical conditions, and detected CH4 flux. In fact, data suggest that phenomena deeper in the soil profile, including deep methanogenesis and gas and carbon releases from melting permafrost, may be more critical than previously thought to net CH4 release from Arctic soils. We now hypothesize that factors such as the depth of the biologically active zone (BAZ) above the permafrost; non-biological permafrost contributions; and the proportional thickness of anaerobic vs. aerobic soil layers may dominate observed CH4 release rates. Specifically, if the BAZ is deep and the anaerobic layer thick relative to the oxic layer, CH4 production will overwhelm CH4 consumption, resulting in elevated CH4 flux to the atmosphere.

In this project, we will test this alternate hypothesis via the following activities:

1. Return to Ny-Ålesund in late summer 2012 to core into and below the BAZ at specific sites with known and contrasting CH4 fluxes. Within these cores, we will quantify absolute methanogen and methanotroph abundances versus depth at each site; determine associated geochemical conditions, CH4 and oxygen profiles, permafrost depths, and permafrost CH4 and carbon content; and measure CH4 flux to correlate soil and permafrost conditions with CH4 released to atmosphere at each site;

2. Statistically compare estimated biological vs. non-biological contributors to the CH4 balance at each site, including the influence of permafrost CH4 and carbon releases associated with melting;

3. Extend local CH4 flux estimates to landscape levels around Ny-Ålesund by measuring CH4 flux at proximal sites radiating away from cored sites to more accurately estimate the relative contributions of different types of landscapes to regional CH4 flux; and

4. Sustain a successful international collaboration with a USA researcher examining methanotroph-methanogen relationships in the Arctic to increase the capacity of current and future work.

The above activities will be fulfilled via an eight-month research plan, including 10 days based at the NERC Arctic Research Station in Ny-Ålesund. Work will be performed in the late summer, which is the period of maximum permafrost thaw, and also a time when the NERC field station tends to be underutilized. A central non-technical goal of this effort will be to gain enough data to support a larger proposal aimed at EU and other international funding agencies.

This project will be of primary importance to researchers studying biogeochemical cycles and climate change. However, underlying discoveries also will be of immediate value to:

1. Environmental regulators responsible for reducing carbon footprints;

2. Industrial biotechnologists that use methane cycle organisms for bioremediation and chemical biosynthesis;

3. Biochemists and medical researchers interested in biomolecules like methanobactin; and

4. The oil industry that uses related biomarkers in environmental management and bioprospecting.

Links already exist between CIs and groups involved with all of these fields, which will be promoted via activity and interactions within this project and the development of a new webpage aimed at disseminating research on methanogen-methanotroph ecology. Specific impacts are as follows.

A top priority at Defra, the Environment Agency, and the Department of Energy and Climate Change is to develop a better understanding of how different landscapes affect greenhouse gas flux to the atmosphere (see http://www.defra.gov.uk/environment/climate/). Although Arctic landscapes superficially differ from UK landscapes, the biological drivers of methane flux are similar. Therefore, any discoveries here will directly answer landscape management questions within the UK. Fortunately, our group has two guest staff members linked with Environment Agency and Defra (Drs Sean Burke and Hugh Potter), who can provide direct links for our results to policymakers at the two agencies.

A deeper understanding of methanogen-methanotroph ecology, which will be gained here, has growing importance to industrial biotechnology and the oil industry. Many new technologies are being developed that require either methane (CH4) or carbon dioxide as the carbon source, such as protein synthesis and biofuel manufacture. As such, factors that affect community selection and function will have direct value to such technologies. Further, methanotrophs and methanogens have unique molecular and chemical signatures, which are now being used for environmental management and prospecting in the oil industry. The CIs already have close associations with companies that use microbial community engineering in product development (Archventure Corporation) and bioprospecting (Envirogene), respectively, which provide immediate opportunity for commercial translation of research results. Finally, Graham's work with methanotrophs and methanobactin (mb) continues to impact medical applications related to copper transport. As examples, mb has been used as a model compound for understanding copper homeostasis in respiratory systems; synthetic analogues have been tested for copper-chelation therapy in patients with copper toxicity or deficiency diseases; and mb has been assessed as a blocking agent for patients with Alzheimer's disease. These extensions will continue as new discoveries are made.

Although results will be reported in high-impact journals and via presentations, CIs also will target new results to the popular media and literature. The CIs all have been interviewed by local (Metro Radio - Newcastle), national (BBC4) and international media sources (NPR in the US, CBC in Canada), which recently continued on 360o, the pre-eminent science news magazine show on TV2 in Switzerland. Further, the PI's work has been included in Discover and Scientific American magazines, and a simplified version of his antibiotic resistance work is included in a new children's book on science. Given this track record, we expect high educational and public interest from this current project. Impact success will be monitored against the following milestones: (1) closer engagement with environment agencies to tailor future regulatory needs; (2) presentation of findings to regulators and educators in non-university settings, including via the new webpage; and (3) increased public engagement through popular articles and local presentations.