The aim of the BMBF-funded collaborative project Glymik (duration Nov. 2020- Oct. 2023) is to demonstrate possible effects of the herbicide glyphosate, one of its formulations (Roundup) and its main metabolite AMPA on brown trout as representatives of aquatic ecosystems. For this purpose, the health status of exposed fish, the integrity of their gut and gill microbiome, and their immunocompetence will be investigated. In the Tübingen subproject, the exposure experiments are performed and the fish are assessed with respect to their health status and specific immune responses. In order to establish causality between chemical exposure and the effects in fish, and to exclude non-specific influences, the effect of the herbicide on the primary molecular target in the fish microbiome will be gradually manipulated or switched off experimentally. The project thus explicitly elaborates mechanistic relationships between exposure to glyphosate, influences on the fish microbiome and responses of a holobiont (i.e. the entirety of the organism fish including its microbiome).