Organic matter storage and decomposition in the hyporheic zone of a mountain stream

Abstract

Dissolved organic carbon (DOC) and particle organic matter (POM) content in hyporheic water and the sediments were measured to examine the function of the hyporheic zone as a storage and decomposition site in a mountain stream. Using the step-pool sequences, the zones of downwelling and upwelling were compared. DOC and Bioavailable DOC concentrations of hyporheic water were higher than stream water, and the DOC concentration increased with hyporheic exchange flux in the downweeling zone. POM in both hyporheic water and sediments were higher at the downwelling zone, suggesting that the hyporheic zone, especially the zone of downewlling, function as a storage and active decomposition site of organic matter. Lower DOC concentrations in the stream channel suggests that POM stored in the hyporheic zone is a source of DOC in the hyporheic water.