The Water Framework Directive (WFD) is the most important piece of water legislation in Europe for many years. It aims at ensuring the ‘good water status’ of EU water bodies and thus achieve both its good chemical and ecological status. To achieve and assess a ‘good ecological status’, the WFD advocates the integration of various disciplines. Its successful implementation raises new challenges, and demands that we make available a set of low-cost tools and techniques to deliver appropriate data. The WFD accounts for chemical and ecological evaluation, but there are no requirements regarding the establishment of cause-effect relationships in the assessment of environmental quality. By incorporating bioassays to ascertain the cause-effect of a failing ecological status in a water body, a more sound approach may be included within the assessment. This project (QWATER) aims to fill this gap, by gauging the ecological relevance of integrating short-term toxicity bioassays into quality elements in the WFD, as these may contribute to our ability to assess and manage European water bodies. To test the projects working hypothesis ‘that bioassays may contribute significantly to our ability to more comprehensively assess and manage water bodies in compliance with the WFD’, ecologically relevant in situ cost-effective toxicity bioassays will first be developed and validated with the aim of achieving a full battery of in situ assays using organisms representative of several key functions at the ecosystem level. Then, modelling tools will be used to verify whether the integration of bioassays as ‘quality elements’ will (or will not) strengthen the robustness of the standard Ecological Quality Status approach to assess water quality.