Recent flume experiments within MOBICOS were conducted to test whether whole-stream and compartment-specific uptake of terrestrial dissolved organic matter (t-DOM) differs between a natural stream (Wormsgraben, Saxony-Anhalt, Germany) and an agricultural stream (Hassel, Saxony-Anhalt, Germany), and to which extent this is driven by different biofilm communities. For that purpose, biofilms were cultured for four weeks in flumes operated as bypasses to the streams, and an isotopically enriched tracer (leachate from rye grass, 99 at% 13C, 15N) was added to both flumes and streams.