The global climate is predicted to go through great changes in the 21st century, which will have impacts on ecosystems all over the world. Aquatic ecosystems will be affected by higher annual temperatures and increased runoff from surrounding terrestrial areas. The increased runoff will cause more terrestrial organic matter (TOM) to reach the waters, which will elevate levels of dissolved organic carbon and nutrients. The higher temperature, changed water color and increased nutrient concentration are together bound to affect aquatic systems, but exactly how the systems will respond is yet unclear. The aim of this study was to investigate how periphyton and benthic grazers will react to higher temperatures and elevated amounts of TOM in the water. This was done by measuring production of periphyton and growth rates of the snail species Gyraulus acronicus when placed in treatments with higher temperature, more TOM or a combination of these two. Higher temperature was found to have a negative effect on periphyton production, while increased amounts of TOM alone had a positive effect, and the combination of these two lowered production. The results on snail performance were in most cases non-significant, but the results still suggest that possible future effects of more TOM and higher temperature on the snails will be negative.