  A novel technique is used to compute the bulk viscosity of high temperature
holographic gauge theory plasmas with softly broken conformal symmetry. Working
in a black hole background which corresponds to a non-trivial solution to the
Navier-Stokes equation, and using a Ward identity for the trace of the
stress-energy tensor, it is possible to obtain an analytic expression for the
bulk viscosity. This can be used to verify the high temperature limit of a
conjectured bound on the bulk viscosity for these theories. The bound is
saturated when the conformal symmetry-breaking operator becomes marginal.
