  Coherence arises from the superposition principle, where it plays a central
role in quantum mechanics. In [Phys.Rev.Lett.114,210401(2015)], it has been
shown that the freezing phenomenon of quantum correlations beyond entanglement,
is intimately related to the freezing of quantum coherence (QC). In this paper,
we compare the behaviour of entanglement and quantum discord with quantum
coherence in two di erent subsystems (optical and mechanical). We use
respectively the en-tanglement of formation (EoF) and the Gaussian quantum
discord (GQD) to quantify entanglement and quantum discord. Under thermal noise
and optomechanical coupling e ects, we show that EoF, GQD and QC behave in the
same way. Remarkably, when entanglement vanishes, GQD and QC re-main almost una
ected by thermal noise, keeping non zero values even for high temperature,
which in concordance with [Phys.Rev.Lett.114,210401(2015)]. Also, we nd that
the coherence associated with the optical subsystem are more robustagainst
thermal noisethan those of the mechanical subsystem. Our results con rm that
optomechanical cavities constitute a powerful resource of QC.
