Comprehension and prediction of ecological effects related to environmental contamination calls for improvement of risk assessment approaches and validation of existing methods. As regards to metals, the prediction of ecological disturbance through the assessment of bioavailability is limited to the use of approaches not successfully validated in situ. Metal-related risk assessments should integrate results from field studies about the relationship between bioavailable concentrations and ecological response. In this aim, 1/ biota (which reflect bioaccumulation and bioavailability) should be used to estimate water contamination level, and 2/ the relationship between concentrations in biota and ecological response should be characterised. The validation of this approach at a wide scale could reveal the existence of a universal threshold for metal concentrations in a given biomonitor above which adverse ecological effects appear. Previous studies mainly rely on passive biomonitoring: the presence of the test organism is required in situ and the influence of confusing factors may be neglected. Active biomonitoring with transplanted organisms collected from the same population enables to overcome these drawbacks. Our work aimed at calibrating the active biomonitor Gammarus fossarum by relating the concentrations measured in in situ caged organisms to local ecological indicators. 129 sites were investigated in France, for which relevant ecological and chemical data were available. Controlled batches of gammarids were exposed during 7 days. Metals were analysed by ICP-MS (Cd, Pb, Ni, Co, Ag, As, Zn, Cr, Cu) or automated AAS (Hg). For most metals, bioaccumulation was significant with ratios between the lowest and the highest values related to the essential or non-essential character of the metals, confirming the relevance of this species to monitor metal contamination in freshwater systems. For all metals, results showed no relationship between bioaccumulation levels and global ecological disturbance. On the contrary, for Cd and Pb, a clear relationship was established between the concentration in caged organisms and the abundance of metal-sensitive invertebrates. Metal concentration in G. fossarum can be quantitatively related to metal-specific adverse responses in stream invertebrates. Dose-response curves, defined for each metal at the national scale, indicate that contamination measured in caged organisms could be used to manage the risk of metallic contamination.