  We investigate the effect of resonances in photoionization and recombination
cross sections computed using the R-matrix method. Photoionization and
recombination rates derived from high-resolution cross sections for oxygen ions
are compared with earlier works with less resolution and accuracy, such as in
the widely used Opacity Project data. We find significant differences in
photoionization rates for O II metastable states, averaged over Planck
functions corresponding to ionizing radiation fields, with respect to the
intrinsic accuracy of the calculations and improved resolution. Furthermore,
for highly charged ions other physical effects are also important.
Recombination rate coefficients, averaged over a Maxwellian distribution, are
extremely sensitive to the position and resolution of near-threshold
resonances, and radiation damping, in (e + O VII) --> O VI + hnu. Surprisingly
however, the effect on the monochromatic and the mean Rosseland and Planck
bound-free opacities is relatively small, but may be potentially significant.
