Presence of Eriophorum scheuchzeri enhances substrate availability and methane emission in an Arctic wetland

► Three groups of LMWOC were analysed, in pore water of an Arctic fen, using LC-MS. ► More than 75% of the LMWOCs consisted of organic acids, whereof ≥85% acetic acid. ► The pore-water concentration of acetic acid would support 2-2.5 h of CH4 flux. ► Species composition had a very strong effect on parts of the C-cycle in the fen. ► Eriophorum dominated plots had higher acetic acid conc., CH4 flux and Reco.