  Protoplanets formed in a marginally gravitationally unstable (MGU) disk by
either core accretion or disk instability will be subject to dynamical
interactions with massive spiral arms, possibly resulting in inward or outward
orbital migration, mergers with each other, or even outright ejection from the
protoplanetary system. The latter process has been hypothesized as a possible
formation scenario for the unexpectedly high frequency of unbound gas giant
exoplanets (free floating planets, FFP). Previous calculations with the EDTONS
fixed grid three dimensional (3D) hydrodynamics code found that protoplanets
with masses from 0.01 $M_\oplus$ to 3 $M_{Jup}$ could undergo chaotic orbital
evolutions in MGU disks for $\sim$ 1000 yrs without undergoing monotonic inward
or outward migration. Here the Enzo 2.5 adaptive mesh refinement (AMR) 3D
hydrodynamics code is used to follow the formation and orbital evolution of
protoplanets in MGU disks for up to 2000 yrs. The Enzo results confirm the
basic disk fragmentation results of the EDTONS code, as well as the absence of
monotonic inward or outward orbital migration. In addition, Enzo allows
protoplanet mergers to occur, unlike EDTONS, resulting in a significant
decrease in the number of protoplanets that survive for 1000 to 2000 yrs in the
Enzo models. These models also imply that gas giants should be ejected
frequently in MGU disks that fragment into large numbers of protoplanets,
supporting ejection as a possible source mechanism for the observed FFPs.
