The decomposition of allochthonous organic matter (AOM) is a critical ecosystem function in streams and supplies resources to stream organisms originally produced via terrestrial photosynthesis. Stressors like salinity can impede the AOM breakdown, thus potentially impairing ecosystems services. In our study we measure the influence of salinisation caused by dryland salinity and a coalmine to leaf decomposition. The sampling sites in the field were selected to exhibit a gradient of salinity from 30 µS/cm to around 13-000 µS/cm from dryland salinity in the Murrumbidgee River Catchment and 100 µS/cm to 2-500 µS/cm from saline pollution from a coal mine in the Georges River Catchment, both in New South Wales. Dried River Red Gum (Eucalyptus camaldulensis) leaves were placed in coarse and fine bags. The leaves in the coarse bags are accessible to invertebrates and microorganisms and the leaves in the fine bags are accessible for microorganisms only. Preliminary results showed greater weight loss of the leaves at low salinity (30 µS/cm) site after just two weeks than at a site with higher salinity (1600 µS/cm). A laboratory study is in progress assessing for the effect of salinity on microbial leaf decomposition eliminating confounding environmental variables. This experiment is using salinities of 100, 1-000 and 10-000 µS/cm sodium chloride, artificial sea water and sodium bicarbonate and inoculating leafs with microbial communities from either a low (30 µS/cm) or a high (13-000 µS/cm) salinity site, in a three factor orthogonal design.