Project leader: Dr. Mia Bengtsson

Peatland microbiomes encompass prokaryotic and eukaryotic microbes that inhabit the peat itself, the water that connects micro- and macro-environments in the landscape, as well as the diverse plant species that make up peatland vegetation. Microbiomes are central in all ecosystem processes leading to or mitigating GHG emissions as they decompose peat, produce N2O, CH4 and CO2, but also consume N2O and CH4 and interact closely with plants that fix C and are responsible for peat formation. Rewetted fens, in contrast to natural fens, feature altered conditions for microbial colonization and activity, such as the formation of shallow water bodies resting on degraded peat. The massive complexity of peatland microbiomes, including the diversity of microbial taxa present, presents a challenge in understanding the underlying processes leading to GHG emissions or accumulation of organic matter. However, the information contained in these diverse communities is an untapped goldmine with power to predict patterns in GHG fluxes if deciphered. As a C store, peat is extremely vulnerable to microbial degradation, therefore it is crucial to understand how microbiomes vary, function, and are transported in the terrestrial-aquatic interfaces of rewetted fens. In subproject B3, we investigate how fen peatland microbiomes vary on regional (WP B3.1) and landscape (WP B3.2) scales and how this variation can be used to predict ecosystem function. On a local scale (WP B3.3), we zoom in on shallow water bodies, a distinct feature of rewetted fens and a hotspot of CH4 emissions, and investigate the role of aquatic macrophytes and their microbiomes for carbon and nutrient cycling during extreme conditions of flooding and drought in the mesocosm experiment MCExp shallow water.