Global salinization is impacting both freshwater and terrestrial systems, and impact from increased salts can change processes within systems and energy and matter exchange between systems. Yet these systems are often studied in isolation. To determine how terrestrial and freshwater salinization changes ecosystem function in riparian nutrient cycling, we initiated a greenhouse mesocosm salinization experiment with paired and connected terrestrial and stream systems, where NaCl was added as 100, 200, 300, 400, 500 mg/L or none as controls (n=5 per treatment) or just streams or just soils at 300 mg/L. Preliminary results on a subset of mesocosms demonstrated that terrestrial (after ~4 months) and stream (after 26 days) decomposition averaged ~49% and ~57% mass loss in open bags and ~43% and ~58% mass loss in closed bags, respectively. For streams, closed and open bags had similar decomposition rates, but NaCl addition up to 400 mg/L tended to slightly increase decomposition. For open bags, the addition of NaCl up to 300mg/L tended to slightly increase decomposition rate relative to controls in terrestrial systems, but had no effect >300mg/L NaCl, whereas any NaCl addition tended to slightly decrease decomposition rate in closed bags relative to controls. The difference in decomposition rate between closed and open bags was greatest when NaCl was added up to 300mg/L. Similarly, soil respiration decreased relative to controls in all NaCl addition treatments. This suggest that soil salinization stimulates detritivores at low levels but suppresses microbial activity. Photosynthesis and ecosystem respiration increased with NaCl additions up to 300mg/L relative to controls resulting in controls having the greatest net ecosystem productivity. Although preliminary, these results suggest a slight sodium subsidy-stress response in both systems.