Ammonia impacts methane oxidation and methanotrophic community in freshwater sediment

Abstract. Lacustrine ecosystems are an important natural source of greenhouse gas methane. Aerobic methanotrophs are regarded as a major regulator controlling methane emission. Excess nutrient input can greatly influence carbon cycle in lacustrine ecosystems. Ammonium is believed to be a major influential factor, due to its competition with methane as the substrate for aerobic methanotrophs. To date, the impact of ammonia on aerobic methanotrophs remains unclear. In the present study, microcosms with freshwater lake sediment were constructed to investigate the influence of ammonia concentration on aerobic methanotrophs. Ammonia influence on the abundance of pmoA gene was only observed at a very high ammonia concentration, while the number of pmoA transcripts was increased by the addition of ammonium. pmoA gene and transcripts differed greatly in their abundance, diversity and community compositions. pmoA transcripts were more sensitive to ammonium amendment than pmoA gene. Methane oxidation potential and methanotrophic community could be impacted by ammonium amendment. This work could add some new sights towards the links between ammonia and methane oxidation in freshwater sediment.