Linking organic carbon cycling within hyporheic zone of a small lowland river and greenhouse gases emissions

Our long-term study revealed that respiration of oxygen, nitrate, sulfate and methanogenesis may simultaneously coexist within the hyporheic zone and that coupling of anaerobic metabolism and methanogenesis appear to be an important pathway in organic carbon cycling in the unpolluted lowland stream Sitka sediments (Czech Republic). At least 80 % of sediment organic matter was respired via anaerobic respiration (denitrification, sulfate and CO₂ reduction). In addition, these processes result in production of excess of the CO₂, CH₄, and N₂O which make the interstitial water supersaturated of those gases with respect to atmosphere and allow their fluxes to overlying water and further to the atmosphere. Totally,  211 t of greenhouse gases were annually emitted to the atmosphere from the water level of the Sitka stream (~ 0.2 km²) with a dominant proportion being CO₂. From the point of view of their ecological role we have suggested that hyporheic sediments represent a sink for some nutrients (e.g. nitrates), while sources of biodegradable DOC for surface stream and gases that are widely believed to affect global climate change.

 Research was supported by a grant NPV II 2B06101 (Czech Republic) and HUFS Faculty Research Grant (Korea).