Rivers are a significant source of greenhouse gases, particularly CH4 and CO2. However, the mechanisms controlling CH4 emissions are not well understood. A key process is the decomposition of organic matter by microbes, which is strongly influenced by sediment redox conditions and riverbed structure. Riverbed clogging, caused by excessive infiltration of fine sediments, reduces vertical connectivity between surface water and the hyporheic zone. This limits O2 availability and promotes anoxic conditions that favour methanogenesis and CH4 emissions. At the same time, however, anaerobic and aerobic methanotrophs can consume CH4 and thereby mitigate its release. Nevertheless, their contribution in clogged river sediments remains unclear. This project aims to determine the effects of riverbed clogging on sediment anoxia, geochemical conditions and the microbial communities involved in CH4 production and consumption. The project will also examine whether measures such as mechanical declogging and the placement of large wood can restore hyporheic connectivity and reduce CH4 emissions.
