Temporal variation of hydrological exchange and hyporheic biogeochemistry in a headwater stream during autumn

Abstract

AbstractThe hyporheic zone is of great interest for stream ecologists because of its role in stream biogeochemical processing. Our study addresses the effects of leaf-litter inputs and varying discharge on surface–hyporheic water exchange and their possible consequences for the hyporheic zone biogeochemistry. Our study was conducted during autumn in Riera de Santa Fe (northeastern Iberian Peninsula), a stream with a well developed deciduous riparian canopy. We placed 15 wells spaced at 5-m intervals longitudinally down the study reach and measured surface and hyporheic nutrient and dissolved O2 (DO) concentrations on 23 sampling dates (15 during the leaffall period and 8 after a flood that washed out 65% of the accumulated leaf biomass). We assessed changes in surface-water exchange and in hyporheic NH4-N and soluble reactive P (SRP) uptake via coinjection of a conservative tracer and nutrients. Compared to surface water, hyporheic water had lower DO, higher SRP and NO3-N concentrations, and similar NH4-N...