Roles of moss species and habitat in methane consumption potential in a northern peatland

Abstract

In northern peatlands with water tables at or near the surface, the Sphagnum moss layer is potentially the only aerobie region where CH₄ oxidation can occur. We hypothesized that mosses with varying physiologies would create different conditions for methane-oxidizing bacteria and, in turn, affect rates of CH₄ consumption. We measured in-vitro CH₄ consumption potential of Sphagnum magellanicum and Sphagnum capillifolium taken from the same habitat and S. magellanicum and Sphagnum majus across habitats to compare and contrast species and environmental effects. In certain cases, S. capillifolium consumed CH₄ more rapidly than S. magellanicum taken from identical habitats, although the greatest difference in consumption rates between species was only 29 μg CH₄ g⁻¹ dry moss d⁻¹, compared to a maximum difference of 126 and 415 μg CH₄ g⁻¹ dry moss d⁻¹ in S. magellanicum and S. majus sampled from different habitats. In most cases, CH₄ was consumed most rapidly in the lower, non-photosynthetic portions of the Sphagnum mosses, and consumption potential increased with an increase in the concentration of CH₄ in the habitat. We hypothesize that CH₄ consumption occurred internally, likely in the hyaline cells, as external surface sterilization did not significantly alter CH₄ consumption rates. This work provides evidence that different Sphagnum moss species have variable ability to oxidize CH₄, although inter-species differences are small compared to differences across habitats.