What causes bubbles in extruded filament?
Oh yeah, that's simple. You are printing too hot and are literally boiling the plastic. Else you have water. However if it was water you would hear Crackling as it printed. If it is too hot you will not hear nearly as much. I am 87.341% sure you are printing too hot.
Looking at your printing temps you are without a doubt printing too hot.
From this link on 3d hubs.

PLA (Only on Replicator 2) Print temp: 210°C (at 100m/s) Notes: heated
bed optional between 40 and 60°C
ABS (Only on Replicator 2X) Print
temp: 230°C (at 100m/s) Notes: heated bed at 110°C