The transport of particles in density-stratified fluids is a ubiquitous feature of natural environments. In the ocean, for example, particles and marine snow move through water columns with pronounced density variations arising from temperature and salinity gradients. Such stratification can significantly modify particle rise or settling rates and promote accumulation near sharp density transitions. Although previous work has largely focused on spherical particles, including their isolated motion, pairwise interactions, and collective transport in stratified fluids, the dynamics of non-spherical bodies with a central aperture remain less explored. Here, we examine the rising dynamics of an annular disc in both homogeneous and linearly stratified fluids using particle-resolved, three-dimensional direct numerical simulations based on an immersed-boundary method in a Cartesian domain. We quantify how the dynamics depend on the Froude and Archimedes numbers, and the diffusivity of the stratifying agent through the Schmidt number.