Sediment bubbling up

[winter999]

I'm just brewing my second batch (Brown Ale) and have noticed something new. I'm now on 10+ days after pitching the yeast and am now in my carboy to condition. Most yeast has already settled to the bottom (no more CO2 production). However, I noticed tiny bubbles rising to the surface. Once there, a small, light colored flake falls off the bubble and sinks to the bottom. I just want someone to confirm I did or did not contaminate my brew.

Thanks!

 

[G. Cretin]

I have seen that in most of my brews and I think what is happening is that some of the yeast are working in the bottom and as they give off Co2 it gets trapped under some of the fallen krausen and floats it up to the top.