The modifications of D(s)-meson spectra in ultrarelativistic heavy-ion collisions are identified as a quantitative probe of key properties of the hot nuclear medium. The unique valence-quark content of the D(s)=cs̄ couples the well-known strangeness enhancement with the collective-flow pattern of primordially produced charm quarks. This idea is illustrated utilizing a consistent strong-coupling treatment with hydrodynamic bulk evolution and nonperturbative T-matrix interactions for both heavy-quark diffusion and hadronization in the quark-gluon plasma (QGP). A large enhancement of the D(s) nuclear modification factor at Relativistic Heavy Ion Collider is predicted, with a maximum of ∼1.5-1.8 at transverse momenta around 2 GeV/c. This is a direct consequence of the strong coupling of the heavy quarks to the QGP and their hadronization via coalescence with strange quarks. We furthermore introduce the effects of diffusion in the hadronic phase and suggest that an increase of the D-meson elliptic flow compared to the D(s) can disentangle the transport properties of hadronic and QGP liquids.