Methane flux and high-affinity methanotrophic diversity along the chronosequence of a receding glacier in Greenland

Methane consumption in upland soils represents an important part of the biologically mediated sink of tropospheric methane. The present study focuses on the role of glacier forefields as a potential methane sink. The role of these environments, though increasing in size, has not yet been taken into account in the global methane budget. Net methane fluxes were analysed based on a static chamber method on a proglacial chronosequence from the Mittivakkat valley, southeast Greenland. Methane uptake could be measured in 7of the 12 study sites, with highest rates in the oldest materials from the chronosequence, suggesting that methane oxidation potential may increase during glacier recession (80–150 years). In the chamber located at the glacier front, net methane production was observed, indicating that the microbial community changes after glacial recession from being net methanogenic to becoming net methanotrophic. Diversity analyses based on denaturing gradient gel electrophoresis (DGGE) from the methanotrophic communities responsible for methane uptake at atmospheric levels demonstrate that methanotrophic microbial diversity changes along the chronosequence and show that there is a tendency to a larger diversity in the oldest part of the chronosequence. Sequencing of DNA retrieved from the DGGE revealed a restricted diversity of the methanotrophic community: GenBank accession numbers HM534684–HM534736.