Yep that's not supposed to be there. That is a pellicle, a protective film that some yeast or bacteria produce n the surface of a substrate to to block out oxygen and protect themselves from other unfriendly 'bugs and or critters'. So...seems like we have a little infection issue in the Berliner Weisse, well I should say a not planned for infection. At this point think I'll let it go and do what its going to do, at least for a few days. Then into the fridge to spend some time cold, that should slow down anything that might be growing in there.
I would guess there is some Brett. at work, but who knows what else might have snuck in, and with some of the things growing in the yeast ranch there it could be anything. Going by the smell, I doubt its anything all too bad, but it is still early, this has only appeared over the last week, since I warmed the beer up.
This only our second infected batch, that I haven't planned on. We had one a few years back on a spiced Scotch Ale, long before we understood what other yeasts and bacteria could offer to the flavor of a beer.
Now how to clean this up. As I said, it doesn't appear to be anything that you can say is 'bad' for you, actually there are not many things that can grow in fermenting wort that could can be harmful, As much as yeast are happy, and a few other organisms, the environment is pretty hostile. The pH of beer can drop pretty low, to the point that many bacteria can't survive. Then there is the presence of alcohol, though this is a small beer(target OG was only 1.038), alcohol becomes toxic as low as 5% by volume. Between the pH and he alcohol content beer is a pretty uncomfortable place to live, so I am not too worried about what is growing. As far as the bucket is concerned, I think this one is retired from regular fermentations, I was planning on marking a bucket 'sour' soon so it looks like this one is it. The last thing will be to replace most of my hoses, they are cheap to replace and an easy way to spread infections.
Well we will have to see how this goes.