In the early successional state of sand-bed streams nascent macrophyte vegetation in the stream corridor is major source of organic carbon. Supply of organic matter from the upland catchment as in mature landscapes is scarce during open land state. This might give particular importance to in-stream vegetation as carbon source fuelling sediment associated respiration. We investigated the effect of macrophyte litter input on microbial respiration in sediments along the hydrological flow path from upland terrestrial to semi-aquatic to permanently aquatic sites of three stream corridors in the artificial catchment Chicken Creek. Results show the major importance of the vegetation derived litter for sediment respiration. In-stream macrophyte vegetation as new source for a higher level of microbial activity indicates the successional transition from open land into macrophyte state within the stream corridors.