  The Parton-Hadron-String-Dynamics (PHSD) transport model is used to study the
impact on the choice of initial degrees of freedom on the final hadronic and
electromagnetic observables in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV.
We find that a non-perturbative system of massive gluons (scenario I) and a
system dominated by quarks and antiquarks (scenario II) lead to different
hadronic observables when imposing the same initial energy-momentum tensor
$T_{\mu \nu}(x)$ just after the passage of the impinging nuclei. In case of the
gluonic initial condition the formation of $s,{\bar s}$ pairs in the QGP
proceeds rather slow such that the anti-strange quarks and accordingly the
$K^+$ mesons do not achieve chemical equilibrium even in central Au+Au
collisions at $\sqrt{s_{NN}}$ = 200 GeV. Accordingly, the $K^+$ rapidity
distribution is suppressed in the gluonic scenario and in conflict with the
data from the BRAHMS Collaboration. The proton and antiproton rapidity
distributions also disfavor the scenario I. Furthermore, a clear suppression of
direct photon and dilepton production is found for the pure gluonic initial
conditions which is not so clearly seen in the present photon and dilepton
spectra from Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV due to a large
contribution from other channels. It is argued that dilepton spectra in the
invariant mass range 1.2 GeV $< M <$ 3 GeV will provide a definitive answer
once the background from correlated $D$-meson decays is subtracted
experimentally.
