<p>Variability in species’ responses to environmental changes (response diversity) is a critical feature in determining stability of ecosystem-level properties. However, quantifying response diversity remains challenging. A key issue is the context-dependent nature of species’ responses: a species reaction to a specific environmental factor can vary depending on other environmental conditions or interactions with other species. Consequently, these responses are dynamic rather than static. We propose a framework to quantify response diversity, incorporating time-variability in species’ responses to biotic and abiotic factors and accommodating high-dimensional, nonlinear interactions in complex systems without assuming equilibrium. Using a 40-year set of monthly data from Lake Geneva, we demonstrate that response diversity of the phytoplankton and zooplankton community stabilizes their respective biomass within but not across trophic levels. Importantly, the stabilizing effect of response diversity varies over time, being context-dependent on time-varying environmental conditions. Our method provides an approach for uncovering mechanisms linking biodiversity and ecosystem dynamics.</p>