Small rain events during drought alter sediment dissolved organic carbon leaching and respiration in intermittent stream sediments

Abstract With climate change, streams and rivers are at increased risk of droughts flow intermittency. The full implications these conditions for fluvial carbon (C) processing stream-atmosphere CO 2 emissions not well understood. We performed a controlled drought experiment in outdoor hyporheic flumes. simulated small rain events that increase sediment moisture content, but do cause streamflow order to investigate how affect streambed dissolved organic C dynamics, biofilm respiration enzyme activity, bacterial community composition. Flumes were subject non-flow phase one month with varying frequency (weekly, 3 × weekly, no rain). Sediment was sampled the surface from zone end phase. quantified microbial dry sediments DOC leaching after resumption. found that, surface, more frequent significantly 12.6 ± 0.25 µg g −1 DW h 26.5 11.3 between control weekly events. average amount leached during resumption reduced by 0.813 0.62 mg L More also resulted fresher DOM tryptophan fluorescence higher BIX. This, along glucosidase activity biofilms, indicates OC period Small enhanced Shannon diversity communities, stronger presence ‘terrestrial-like’ clades. propose drought, even those size, highly relevant Future research should explicitly consider when investigating fluxes intermittent fully understand systems change. conclude impact dynamics reflow likely cascading downstream river network.