Strange Particles on top of bubble coloum

I don't know if you can see it, but on top of the bubble coloum there are dark blue circles. they are animated like they are poping or something like that. I don't know if they are any new feature or something like that but just posted it, coz I couldn't find this bug/feature....

I did search but couldn't find this bug/feature.

Take a look at the photos and a short video......