Chemical stressors are increasingly recognized as drivers for ecosystem deterioration by modifying interactions within food webs (horizontal vs. vertical interactions). At the same time, mechanisms indirectly leading to effects at higher trophic levels in aquatic food webs are not well understood. With this presentation, I will discuss the impact of chemicals on the base of heterotrophic food webs, namely communities of heterotrophic microorganisms (mainly bacteria and fungi) that colonize detritus (such as leaves) and how these communities adapt to those chemical exposure. I will also highlight what the consequent modifications in community composition mean for the ecosystem functions these microorganisms perform. The central ecosystem functions are besides the decomposition of organic material, the provisioning of nutrients and energy to higher trophic levels feeding on detritus. The latter function is triggered by the softening of leaf tissue as well as the production and concentration of essential nutrients such amino and fatty acids. Although, still at its infancy, I will close with an outlook on the potential bottom-up or top-down directed effects induced in terrestrial food webs as a consequence of chemical stress driven changes in heterotrophic aquatic systems through cross ecosystem subsidy.